- Email: [email protected]
Total synthesis of dysidavarone A
Accepted Manuscript Total synthesis of dysidavarone A Chunhui Yu, Xiaoguang Zhang, Jinghua Zhang, Zhengwu Shen PII:
S0040-4020(16)30490-2
DOI:
10.1016/j.tet.2016.05.073
Reference:
TET 27800
To appear in:
Tetrahedron
Received Date: 15 April 2016 Revised Date:
24 May 2016
Accepted Date: 30 May 2016
Please cite this article as: Yu C, Zhang X, Zhang J, Shen Z, Total synthesis of dysidavarone A, Tetrahedron (2016), doi: 10.1016/j.tet.2016.05.073. This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
ACCEPTED MANUSCRIPT
Total Synthesis of Dysidavarone A
†
School of Medicine, Shanghai Jiao Tong University, Shanghai 200025, People’s Republic of China
Shanghai University of Traditional Chinese Medicine, Shanghai 201203, People’s Republic of China
M AN U
SC
‡
RI PT
Chunhui Yu#, ‡, Xiaoguang Zhang #, ‡, Jinghua Zhang#,† and Zhengwu Shen*,†
ABSTRACT. Dysidavarone A is a sesquiterpene isolated from the South China Sea sponge Dysidea avara and was reported that it showed significant anticancer activities. Because the compound has unique “dysidavarane” carbon skeleton and potent biological activity, a seven-step stereoselective synthesis of dysidavarone A was developed. The key steps of the synthesis involved stereoselective intramolecular
α-arylation
TE D
reductive-alkylation,
and
double
bond
migration
reaction.
The
anti-proliferation activities of Dysidavarone A against human kidney carcinoma cell lines 786-O and
EP
human prostate cancer cell lines PC-3 were also assessed.
AC C
During the past three decades, many natural products containing quinone or hydroquinone skeleton have been isolated from marine sponges.1,2 Most of those compounds were reported to have interesting biological activities including antibacterial, antitumor, antifungal and anti-inflammatory activities.3,4 Dysidavarone A is one of the quinone sesquiterpene isolated from the South China Sea sponge Dysidea
*
#
To whom correspondence should be addressed. Tel:+86-21-64457997. E-mail: [email protected]. These authors contributed equally to the paper.
1
ACCEPTED MANUSCRIPT
avara. The compound was reported to have potent antiproliferation activities against four human cancer cell lines.5 Due to its unique three-dimensional architecture of tetracyclic core and promising biological activity, dysidavarone A has become thetarget of synthetic laboratories. So far, there are two groups who
RI PT
have completed the total synthesis of dysidavarone A.6 Herein, we report our studies of the total synthesis of dysidavarone A from a commercial available starting material 2-methyl cyclohexanone-1, 3-dione. Although our synthetic strategy was similar to the Menche’s synthesis6a, the use of less steric hindered 3,
SC
5-diethoxyl benzyl bromide 22 as the alkylation agent, not only improved the yield of reductive alkylation reaction, but also circumvented the deprotection step through direct oxidization of the phenol moiety into
M AN U
quinone (2). Hence the overall yield of the synthesis was significantly improved. In addition, the antiproliferation activities of dysidavarone A and its derivatives (Figure 1) against human kidney
AC C
EP
TE D
carcinoma cells 786-O and human prostate cancer cells PC-3 were also presented.
.
Figure 1. Dysidavarone A and its derivatives
RESULTS AND DISCUSSION Our initial retrosynthetic analysis of dysidavarone A is outlined in Scheme 1. The two double bonds of Dysidavarone A can be easily obtained from the Wittig olefination of 4, 8-diketone of compound 5 with
2
ACCEPTED MANUSCRIPT
the subsequent double bond isomerization. The quinone moiety of the dysidavarone A can be derived from the aromatic ring of compound 5. The compound 5 was envisioned to be synthesized through the alpha arylation reaction from compound 6. The strategy used for appending the aromatic moiety to the bicyclic
RI PT
sesquiterpene skeleton is well documented 7 and is based upon the stereoselective reductive alkylating of an enone derivative 8 with a substituted benzyl bromide. The Wieland-Miescher ketone analogue 8 could
SC
be readily obtained from 2-methylcyclohexane-1, 3-dione in three steps.8
O
H
OEt
H
OEt
M AN U
OEt
O
O
O
Dysidavarone A (1)
H
O
OEt
OEt
OEt
O O Br
Br
TE D
O
OEt
Br
OEt
6
OEt
5
OEt 7
+ O
O 8
EP
Scheme 1. Retrosynthetic Analysis of Dysidavarone A
Based on above retrosynthetic analysis, our initial synthetic approach started from the preparation of
AC C
compound 7 and compound 8. As illustrated in Scheme 2, the Wieland-Miescher ketone analogue 8 was prepared smoothly from commercially available 2-methyl cyclohexanone-1,3-dione 9 in three steps with 93.2% ee according to a previously reported procedure.8 The substituted benzyl bromide 7 was obtained from orcinol in five steps with 61.8% overall yield. The key reactions used for the synthesis of compound 7 involving Vilsmeier-Haack reaction, Baeyer-Villiger oxidation and double-bromination with NBS.
3
ACCEPTED MANUSCRIPT
9
O L-phenylalanine (+)-CSA/DMF rt to 70 oC 85%
O
O
Et2(SO4)2
OH 12
Et2(SO4)2
OEt EtO
K2 CO3, Acetone 10 h 96%
90%
O
O
11
H2O2-KHSO4 EtO
DMF, 100 oC, 1 h OEt 13
MeOH rt, 4 h OEt O
91%
14 OEt
3.2 eq NBS EtO
Br
hv, CCl4, 6 h
O 8
POCl3 EtO
EtO
K2CO3, Acetone 18 h 97%
O
DCM, rt, 48 h
10
HO
TsOH, MEG
RI PT
TEA, EtOAC 70 oC, 10 h 94%
O
O
90%
OH
OEt 15
SC
O ethyl vinyl ketone
Br 81%
OEt 7
M AN U
OEt 16
Scheme 2. The Synthesis of Compound 7 and 8
Having the compound 7 and compound 8 in hand, as illustrated in Scheme 3, we began to explore the
TE D
reductive alkylation reaction and try to synthesize the key intermediate 6. However, despite of various reaction conditions screened,9 the yield of the reaction is very poor, only small amounts of compound 6 was obtained (8%). Although, the compound 6 can be converted into 18 in 72% yield, the exceptional low
EP
yield of 6 prompted us to focus our investigation on the reductive alkylation reaction.
The stepwise
approach of this reaction was examined, the stereoselective Birch reduction of compound 7 went on
AC C
smoothly and gave the ketone 17 as a single isomer in 89% yield. However, the subsequent alkylation reaction was not successful even under vigorous reaction condition.
4
ACCEPTED MANUSCRIPT
Li, NH3, THF, -78 oC to -33 oC, 7, 8%
o
7
O
-78 C to -33 C O
89%
O 8
various conditions
O O Br 6
17 OEt
H
O
2h 88%
OEt
OEt
H
OEt 3N HCl, THF O
O
O
OEt O
O
OEt 5
18 OEt
H
O
H
OEt
OEt
M AN U
OEt
Pd(OAc)2, PPh3 OEt THF, 100 oC, 24 h 72%
SC
O
OEt
H
O
o
RI PT
H
O Li, NH3,THF
O
OEt
Dysidavarone A
19
Scheme 3. The Initiate Synthetic Approach
TE D
We anticipated that the low efficiency of the alkylation is due to the steric hindrance of the ortho-substitutions on the aromatic ring of the benzyl bromide.7 Hence, the less steric hindrance alkylating agent, 3, 5-diethoxyl benzyl bromide 22 was selected as the alkylation agent for the reaction (Scheme 4).
EP
The 3, 5-diethoxyl benzyl bromide 22 was readily synthesized from compound 20 in two steps quantitatively. The reaction between compound 8 and compound 22 went on smoothly and the key
AC C
intermediate 23 was obtained in 82% yield under standard reductive-alkylation condition. Since compound 8 has 5β-Me configuration (Scheme 5), the initial stereoselective hydride SN2 addition at position 10 and the sequent alkylation occurred from the less hindered α-face of the anion intermediate to form compound 23 stereoselectively (dr>19:1). The stereochemistry of 23 was confirmed by two-dimensional NMR spectroscopic methods. The dibromo-substituted compound 24 could also be used as the alkylation agent in the reductive alkylation reaction and the compound 25 was obtained in 60% yield. These results indicated that the size of the substituent at the ortho position of benzyl bromide is the
5
ACCEPTED MANUSCRIPT
main factor which affect the yield of this reaction. The bromination of compound 23 with NBS in methylene chloride gave the compound 25 as the only product in 92% yield. EtO Et2(SO4)2
OEt PBr3, Py
EtO
OEt
OH 21
20
98%
NBS DCM, 0 oC, 1 h 92%
SC
8 OEt Li, NH3,THF OEt
tBuONa, Diox 100 oC, 4 h 88%
O O
O
OEt
OEt 28
O
OEt O Br OEt
25
Ph3PCH3Br
OEt
tBuOK, toulene 40 h 90%
O
92%
OEt
27
CrO3
O
H
OEt
AcOH, H2 O 0 oC, 0.5 h 68%
TE D
OEt
H
3N HCl, THF 2h
26
H
M AN U
OEt
x-phos, Pd2(dba)3
H
O
60%
24
H
O
-78 oC to -33 oC
Br
OEt
23
NBS DCM, 0 oC, 1 h 91%
Br
OEt
O O
82%
Br 22
H
O
-78 oC to -33 o C
DCM, rt, 4 h
K2CO3, Acetone 18 h 97% OH
8 Li, NH3,THF
RI PT
OH
HO
2
p-TsOH
H
O OEt
AcOH, rt, 12 h O
92%
O Dysidavarone A
EP
Scheme 4. The Total Synthesis of Dysidavarone A
AC C
The palladium catalyzed intra-molecular cyclization of compound 25 gave the tetracyclic core of the dysidavarone A in a stereospecific manner in 88% yield. The dioxolane protecting group of compound 26 was removed in the presence of 3N hydrochloric acid in 92% yield and a subsequent Wittig reaction formed two exocyclic double bonds in one step in 90% of yield.10 The key step for accomplishing the synthesis is to convert the aromatic ring into quinone moiety without affecting the allylic positions of two exocyclic double bonds. Due to the substitution pattern on the aromatic ring of compound 28, compound 2 was expected as the only product of oxidation. Various oxidants including CAN, salcomine and CrO3
6
ACCEPTED MANUSCRIPT
were screened. Finally, the CrO3 was selected as which successfully accomplished the desired oxidation and gave compound 2 in 68% yield.11 The final step for the synthesis of dysidavarone A is to convert the exocyclic double bond at position 4 of compound 2 into endo-double bond. Again, various acids and
RI PT
Lewis acids were investigated which includes RuCl3, RhCl3.3H2O, PTSA, TFA and HCl. Eventually, PTSA in AcOH was found to be the best conditions for such double bond migrate reaction, and compound
+e
O
O
O
O
O
.
.
Protonation
M AN U
8
- .
Li, NH3
SC
2 was successfully converted into dysidavarone A in 90% yield.12
O
O
8b
8a
OH
O 8c
X R
OH
-
H
O
23
+e
O
O
O
TE D
O
8d
8e
EP
Scheme 5. The Stereochemistry of Reductive Alkylation
The synthetic dysidavarone A obtained is identical in all respects (NMR, IR, and MS) to natural
AC C
dysidavarone A. The total synthesis of dysidavarone A described above requires seven steps from readily available diketone 8 and proceeds in 34% overall yield. Upon we were finishing this synthesis, Menche’s group published the first total synthesis of dysidavarone A with a similar strategy. Compared with Menche’s synthesis, this synthesis used a less steric hindered 3, 5-diethoxyl benzyl bromide 22 as the alkylation agents, not only improved the yield of reductive alkylation, but also omitted the deprotection step through direct oxidize the phenol moiety into quinone. The methyl derivative 4 was also obtained according the same procedure from compound 8 in seven steps in 33% overall yield (Scheme 6).
7
ACCEPTED MANUSCRIPT
O Li, NH3,THF -78 oC to -33 oC OMe 83% 29
H
H
O
8
H
OMe
OMe
90%
3
M AN U
AcOH, rt, 12 h O
OMe
SC
O
H
O
32
CrO3 0 oC, 0.5 h AcOH, H2O 67%
p-TsOH
OMe
O
O
OMe 33
Pd(OAc)2, PPh3 THF, 100 o C, 24 h
H
2 h, 93%
O
OMe
OMe
3N HCl, THF
O
34
O
O Br 31 85%
tBuOK, toulene 40 h, 92% OMe
OMe
O
91%
OMe
30
H
O
DCM, 0 oC, 1 h
O
OMe Ph3PCH3Br
H
NBS
OMe
RI PT
OMe
Br
O
4
Scheme 6. The synthesis of methyl derivative of Dysidavarone A
TE D
The compounds synthesized above were assessed for the anti-proliferation activities against renal cancer cell lines 786-O and prostate cancer cell lines PC-3. The GI50 of the compounds were listed in
Conclusions
EP
Table 1. All these four compounds tested showed moderate anti-proliferation activities.
AC C
In conclusion, dysidavarone A was successfully synthesized in seven steps starting from known building block 8. Compared with Menche’s approach, this synthesis used a less steric hindered 3, 5-diethoxyl benzyl bromide 22 as the alkylation agents, not only improved the yield of reductive alkylation, but also omitted the deprotection step through direct oxidize the phenole moiety into quinone, thus the overall yield of the synthesis was significantly improved.
8
ACCEPTED MANUSCRIPT
Table 1 The Anti-proliferation Activities of dysidavarone A and Its Derivatives 786-Oa GI50
PC-3b GI50
Compound (µM)
Dysidavarone A (1)
3.71
6.71
2
6.12
3
6.37
4
3.58
7.19
7.05 5.61
SC
<0.02
Taxol
<0.02
786-O (Human kidney carcinoma cells). b
M AN U
a
RI PT
(µM)
PC-3 (Human prostate cancer cells).
Experimental Section
TE D
General Experimental Procedures. Optical rotation was measured with a Perkin-Elmer 341 MC polarimeter. HR-EIMS spectra were obtained with a Q-TOF Micro LC-MS-MS spectrometer, and ESI-MS spectra with an Agilent 1100 1946 DLC-MS spectrometer. NMR spectra were acquired on a
EP
Varian INOVA 400 MHz and Bruker AM-400 spectrometer with TMS as the internal standard. Data are reported as follows: chemical shift, multiplicity (s = singlet, d = doublet, t = triplet, dd = doublet of
AC C
doublet, b = broad, q = quartet, m = multiplet). Infrared spectra were measured using film KBr pellet techniques and were acquired using a Shimadzu FTIR-8400S spectrometer. Column chromatography (CC) separations were carried out using silica gel H60 (300-400 mesh, Qingdao Haiyang Chemical Group Corp.). 786-O and PC-3 cells were obtained from Shanghai Institute of Material Medica of Chinese Academy of Sciences and were grown in RPMI-1640 and DMEM/F12 medium containing 5% fetal bovine serum.
9
ACCEPTED MANUSCRIPT
2-methyl-2-(3-oxopentyl)cyclohexane-1, 3-dione (10): To a solution of 2-methyl-1, 3-cyclohexadione (9) (3.6 g, 28.7 mmol) in ethyl acetate (200 mL) were added triethylamine (5.2 mL, 37.3 mmol) and ethyl
RI PT
vinyl ketone (3.1 mL, 31.2 mmol). The reaction mixture was heated at 70 °C for 10 hrs and then cooled to 25 °C. The solvent was removed under reduced pressure and the residue was purified by column chromatography eluted with petroleum ether/ethyl acetate (1:2) to give triketone 10 (5.74 g, 94%) as a
SC
pink oil. 1H NMR (400 MHz, CDCl3) δH: 2.76-2.68 (m, 2H), 2.65-2.57 (m, 2H), 2.40 (t, J=7.2 Hz, 1H), 2.32-2.28 (t, J=7.2, 7.6 Hz, 2H), 2.08-1.99 (m, 3H), 1.94-1.84 (m, 1H), 1.22 (s, 3H), 1.02 (t, J=8.0 Hz,
M AN U
3H); 13C NMR (100 MHz, CDCl3) δc: 209.8, 209.6, 63.9, 37.3, 36.5, 35.5, 29.3, 19.3, 17.1, 7.2. IR (KBr) νmax: 2976, 2939, 1716, 1686, 1458, 1375, 1364, 1340, 1319, 1115, 1026 cm-1; MS [M+H]+ m/z (%): 211.2 (80).
TE D
(S)-5, 8a-dimethyl-3, 4, 8, 8a-tetrahydronaphthalene-1, 6 (2H, 7H)-dione (11): A solution of the triketone 10 (2.9 g, 13.6 mmol), L-α-phenylalanine (2.26 g, 13.6 mmol) and D-camphorsulfonic acid (1.58 g, 6.8 mmol) in DMF (30 mL) was stirred at 25 °C under argon atmosphere overnight. The mixture was then
EP
heated at 30 °C for 24 hrs, and the temperature was raised in 10 °C intervals every 24 hrs in 4 days. Then the mixture was stirred at 70 °C for additional 24 hrs. The reactant was poured into cold 5% aqueous
AC C
solution of NaHCO3 (100 mL), extracted with ethyl ether (2 × 60 mL), then dried over anhydrous Na2SO4. After removal solvent under reduced pressure, the residue was purified by column chromatography eluted with petroleum ether/ethyl acetate (1:3) to give enone 11 (2.22 g, 85%) as a light yellow oil. [α]D25+132 (c 0.85, CHCl3); 1H NMR (400 MHz, CDCl3) δH: 2.88-2.82 (m, 1H), 2.67-2.63 (m, 1H), 2.53-2.39 (m, 4H), 2.16-2.03 (m, 3H), 1.80 (s, 3H), 1.78-1.74 (m, 1H), 1.41 (s, 3H); 13C NMR (100 MHz, CDCl3) δc: 212.3, 197.9, 158.4, 130.9, 50.9, 37.6, 33.5, 29.8, 27.5, 23.6, 21.7, 11.5. IR (KBr) νmax: 2974, 2943, 1709, 1647,
10
ACCEPTED MANUSCRIPT
1635, 1448, 1420, 1375, 1362, 1317, 1167, 1026 cm-1; MS [M+H]+ m/z (%): 193.2 (100).
(S)-5', 8a'-dimethyl-3', 4', 8', 8a'-tetrahydro-2'H-spiro{[1, 3]dioxolane-2, 1'-naphthalen}-6'(7'H)-one (8):
RI PT
To a solution of compound 11 (1.75 g, 9.1 mmol) in DCM (17 mL), 2-ethyl-2-methyl-3-dioxolane (17 mL), ethylene glycol (60 mg, 0.9 mmol) and p-toluenesulfonic acid (180 mg, 0.9 mmol) were added. The solution was stirred at 25 °C for 48 hrs, and then the mixture of triethylamine (1 mL) in DCM (60 mL)
SC
were added. The organic phase was washed with saturated aqueous NaCl solution and dried over anhydrous Na2SO4. The solvent was removed under reduced pressure and the residue was purified by
M AN U
column chromatography eluted with petroleum ether/ethyl acetate (5:1) to give compound 8 (1.94 g, 90%) as a light yellow oil. [α]D25+115 (c 0.52, MeOH); 1H NMR (400 MHz, CDCl3) δH: 3.98-3.90 (m, 4H), 2.76-2.63 (m, 1H), 2.53-2.37 (m, 2H), 2.24-2.10 (m, 2H), 1.93-1.57 (m, 8H), 1.33 (s, 3H); 13C NMR (100 MHz, CDCl3) δc: 198.9, 160.4, 130.4, 113.0, 65.6, 65.3, 45.5, 33.9, 29.9, 26.75, 26.71, 21.7, 21.1, 11.7;
(100).
TE D
IR (KBr) νmax: 2941, 2856, 1707, 1686, 1458, 1175, 1262, 1032, 950 cm-1; MS [M+H]+ m/z (%): 237.2
EP
3, 5-Diethoxytoluene (13): See compound 21 for similar procedure. Compound 13 was obtained as pale yellow oil in 97% yield; 1H NMR (400 MHz, CDCl3) δH: 6.32 (d, J=1.6 Hz, 2H), 6.27 (s, 1H), 4.01 (q,
AC C
J=6.8 Hz, 4H), 2.28 (s, 3H), 1.39 (t, J=6.8 Hz, 6H); 13C NMR (100 MHz, CDCl3) δc: 160.2, 140.3, 107.8, 98.7, 63.5, 22.0, 15.1; IR (KBr) νmax: 2980, 2922, 1593, 1470, 1391, 1342, 1319, 1292, 1169, 1157, 1065, 818, 687 cm-1; MS [M+H]+ m/z (%): 181.1 (100).
2, 4-diethoxy-6-methylbenzaldehyde (14): A solution of phosphoryl chloride (12.1 mL, 130.6 mmol) in dried DMF (24 mL) was added to a stirred solution of 3, 5-Diethoxytoluene (19.6 g, 108.8 mmol) in 34
11
ACCEPTED MANUSCRIPT
mL of dried DMF at 100 - 110 oC over a period of 30 min under nitrogen atmosphere. Continue stirring at 100-110 oC for 1 hr, the reaction mixture was poured into ice-water. The pH of the aqueous solution was adjusted to pH 8 with saturated aqueous K2CO3 solution. The precipitate formed was collected and dried
RI PT
to afford 2, 4-diethoxy-6-methylbenzaldehycle (14) (20.6 g, 91%) as an off-white solid. Mp. 92-94 oC; 1H NMR (400 MHz, CDCl3) δH: 10.5 (s, 1H), 6.28 (s, 2H), 4.08 (q, J=7.2 Hz, 4H), 2.55 (s, 3H), 1.45 (t, J=6.8, 7.2 Hz, 6H); 13C NMR (100 MHz, CDCl3) δc: 190.9, 164.9, 164.0, 144.7, 117.5, 109.4, 97.1, 64.5, 63.9,
SC
22.5, 14.9, 14.8; IR (KBr) νmax: 2934, 2860, 2777, 1749, 1663, 1603, 1576, 1558, 1456, 1396, 1325, 1292,
M AN U
1163, 1115, 1057, 849, 837, 787, 700, 507 cm-1; MS [M+H]+ m/z (%): 209.2 (100).
2, 4-diethoxy-6-methylphenol (15): KHSO4 (2.53 g, 18.6 mmol) and 10% of H2O2 (11.6 mL, 114.0 mmol) were added to a solution of 14 (19.3 g, 92.7 mmol) in methanol (500 mL) sequentially at 4 oC. The mixture was stirred at 25 °C for 4 hrs, 5% aqueous solution of KHSO3 (15 mL) was added to quench the
TE D
reaction and the solvent was removed under reduced pressure. The residue was extracted with EtOAc (2 × 350 mL), the extract was washed with water (2 × 150 mL) and dried over Na2SO4. The solvent was removed under reduced pressure to give 15 (16.4g, 90%) as a light yellow solid. Mp. 116-118 oC; 1H
EP
NMR (400 MHz, CDCl3) δH: 6.34 (d, J=2.4 Hz, 1H), 6.27 (d, J=2.4 Hz, 1H), 5.32 (s, 1H), 4.08 (q, J=6.8 Hz, 2H), 3.98 (q, J=6.8 Hz, 2H), 2.23 (s, 3H), 1.44 (t, J=6.8, 7.2 Hz, 3H), 1.39 (t, J=6.8 Hz, 3H);
13
C
AC C
NMR (100 MHz, CDCl3) δc: 151.4, 145.3, 137.5, 123.1, 106.9, 97.7, 64.0, 63.5, 15.3, 14.5, 14.4; IR (KBr) νmax: 3433, 2924, 2853, 2856, 2362, 1655, 1657, 1458, 1465, 1240, 669 cm-1; MS [M+H]+ m/z (%): 197.3 (100).
1, 2, 5-triethoxy-3-methylbenzene (16): See compound 21 for similar procedure. Compound 16 was obtained as colorless oil in 96% yield; 1H NMR (400 MHz, CDCl3) δH: 6.33 (d, J=2.4 Hz, 1H), 6.27 (d,
12
ACCEPTED MANUSCRIPT
J=2.0 Hz, 1H), 4.03-3.92 (m, 6H), 2.24 (s, 3H), 1.44-1.33 (m, 9H);
13
C NMR (100 MHz, CDCl3) δc:
155.1, 152.8, 140.9, 132.3, 106.9, 99.6, 68.5, 64.3, 63.8, 16.7, 15.9, 15.1; IR (KBr) νmax: 3433, 2930, 2361,
RI PT
2330, 1707, 1466, 1331, 1117, 1072, 669 cm-1; MS [M+H]+ m/z (%): 225.1 (20).
2-bromo-3-(bromomethyl)-1, 4, 5-triethoxybenzene (7): To a solution of 16 (8.0 g, 35.7 mmol) in CCl4 (600 mL) was added AIBN (293 mg, 1.79 mmol) and NBS (20.4 g, 114.3 mmol). The mixture was
SC
refluxed for 4 hrs in the presence of light. The precipitate was filtered off and the filtrate was concentrated under reduce pressure to give the crude product. The residue was washed with 30 mL petroleum ether
M AN U
(containing 10% of ethyl acetate) to give compound 7 (11.0 g, 81%) as a pale yellow solid. Mp. 121-125 o
C; 1H NMR (400 MHz, CDCl3) δH: 6.51 (s, 1H), 4.75 (s, 2H), 4.15 (q, J=6.8, 7.2 Hz, 2H), 4.06 (q, J=6.8
Hz, 4H), 1.45-1.40 (m, 9H);
13
C NMR (100 MHz, CDCl3) δc: 151.6, 151.2, 141.4, 131.6, 104.9, 100.8,
68.9, 65.3, 64.2, 28.2, 15.2, 14.4; IR (KBr) νmax: 2976, 2934, 2889, 1558, 1657, 1458, 1419, 1387, 1339,
TE D
1244, 1215, 1115, 1034, 1003, 927, 881, 806 cm-1; MS [M+H]+ m/z (%): 381.0 (65).
(4a'S, 5'S, 8a'S)-5', 8a'-dimethylhexahydro-2'H-spiro [[1, 3]dioxolane-2, 1'-naphthalen]-6'(7'H)-one (17):
EP
A solution of compound 8 (200 mg, 0.85 mmol) and H2O (15.3 µL, 0.85 mmol) in THF (2 mL) was added drop wise to a solution of Li (24 mg, 3.4 mmol) in liquid ammonia (5 mL) at -78 °C in 30 min. The
AC C
reaction mixture was stirred at -35 °C for 1 hr. The reaction was quenched with ammonium chloride (500 mg). 10 mL H2O was added into the mixture and then extracted with ethyl ether (2 × 10 mL). The combined organic layer was dried over anhydrous Na2SO4 and concentrated under reduced pressure. The residue was purified by column chromatography eluted with petroleum ether/ethyl acetate (5:1) to give 17 (180 mg, 89%) as a colourless oil. [α]D25 −3.6 (c 0.96, CHCl3); 1H NMR (400 MHz, CDCl3) δH: 3.94-3.84 (m, 4H), 2.42-2.33 (m, 2H), 2.24-2.19 (m, 1H), 1.90-1.89 (m, 1H), 1.76-1.46 (m, 7H), 1.22 (s, 3H). 0.97(d,
13
ACCEPTED MANUSCRIPT
J=6.4 Hz, 3H);
13
C NMR (100 MHz, CDCl3) δc: 212.8, 112.5, 65.1, 64.9, 48.1, 44.9, 42.4, 37.5, 30.7,
29.9, 24.9, 22.7, 14.2, 11.7; IR (KBr) νmax: 2951, 2878, 1700, 1445, 1186, 1086, 1040, 916 cm-1; MS
RI PT
[M+H]+ m/z (%): 239.2 (100).
(4a'S, 5'S, 8a'S)-5'-(2-bromo-3, 5, 6-triethoxybenzyl)-5', 8a'-dimethylhexahydro-2'H-spiro [[1, 3] dioxolane-2, 1'-naphthalen]-6' (7'H)-one (6): See compound 23 for similar procedure. Compound 6 was
SC
obtained as white solid in 8% yield; Mp. 147-152 oC; [α]D25+29 (c 0.07, EtOH); 1H NMR (400 MHz, CDCl3) δH: 6.50 (s, 1H), 4.08-3.91 (m, 9H), 3.83-3.81 (m, 1H), 3.33 (d, J=13.6 Hz, 1H), 3.07 (d, J=13.6
Hz, 3H), 1.02 (s, 3H), 1.01 (s, 3H);
13
M AN U
Hz, 1H), 2.97-2.92 (m, 1H), 2.97-2.92 (m, 1H), 2.34-2.28 (m, 3H), 1.70-1.39 (m, 16H), 1.34 (t, J=6.8, 7.2 C NMR (100 MHz, CDCl3) δc: 215.4, 150.9, 150.6, 142.5, 132.1,
112.6, 107.6, 101.1, 67.8, 65.3, 64.9, 64.5, 64.1, 51.1, 47.3, 41.6, 40.1, 34.2, 29.3, 29.1, 22.6, 22.3, 17.8, 15.3, 14.5, 14.4; IR (KBr) νmax: 3369, 2928, 2864, 2361, 1709, 1578, 1383, 1339, 1232, 1184, 1117, 1074,
TE D
951, 810 cm-1; HRMS [M+Na]+ m/z 561.1796 (calc. 561.1822 for C27H39BrNaO6).
(4aS, 5S, 11S, 12aS)-7, 8, 10-triethoxy-5, 12a-dimethyl-3, 4, 4a, 5, 6, 11, 12, 12a-octahydro-2H-spiro [5,
EP
11-ethanodibenzo [a, e] [8] annulene-1, 2'-[1, 3] dioxolan]-13-one (18): See compound 32 for similar procedure. Compound 18 was obtained as pale yellow foam in 72% yield; [α]D25+37 (c 0.075, EtOH); 1H
AC C
NMR (400 MHz, CDCl3) δH: 6.40 (s, 1H), 4.07-3.77 (m, 10H), 3.66 (d, J=8.8, 13.2 Hz, 1H), 1.62-1.31 (m, 15H), 1.17 (s, 3H), 0.99 (s, 3H); 13C NMR (100 MHz, CDCl3) δc: 220.7, 151.4, 149.9, 139.2, 128.2, 123.7, 111.8, 97.6, 67.7, 64.7, 63.9, 63.4, 46.3, 46.1, 43.3, 42.2, 41.4, 38.6, 29.1, 22.7, 21.9, 17.5, 17.4, 15.3, 14.6, 14.5; IR (KBr) νmax: 2978, 2935, 2880, 2359, 2332, 1718, 1597, 1383, 1331, 1229, 1184, 1072, 1053, 914, 802 cm-1; HRMS [M+Na]+ m/z 481.2583 (calc. 481.2561 for C27H38NaO6).
14
ACCEPTED MANUSCRIPT
(4aR, 5S, 11S, 12aS)-7, 8, 10-triethoxy-5, 12a-dimethyl-2, 3, 4, 4a, 5, 6, 12, 12a-octahydro-5, 11-methanodibenzo [a, e] [8] annulene-1, 13 (11H)-dione (5): See compound 27 for similar procedure. Compound 5 was obtained as light yellow solid in 88% yield; Mp. 167-170 oC; [α]D25+12 (c 0.065, EtOH); H NMR (400 MHz, CDCl3) δH: 6.39 (s, 1H), 4.07-3.84 (m, 7H), 3.75 (d, J=9.2 Hz, 1H), 3.39 (d, J=17.2
RI PT
1
Hz, 1H), 2.63 (d, J=14.4 Hz, 1H), 2.55-2.49 (m, 3H), 2.22-2.02 (m, 4H), 1.84-1.78 (m, 3H), 1.46-1.25 (m, 12H), 1.09 (s, 3H); 13C NMR (100 MHz, CDCl3) δc: 219.0, 213.4, 151.5, 150.1, 138.9, 127.5, 123.0, 97.4,
SC
67.8, 64.1, 63.3, 49.2, 46.9, 46.5, 43.0, 41.6, 39.9, 37.2, 24.9, 22.8, 19.4, 17.5, 15.2, 14.5, 14.4; IR (KBr) νmax: 2976, 2938, 2872, 2361, 1718, 1701, 1597, 1470, 1387, 1331, 1232, 1128, 1072, 1036, 974, 800 cm-1;
M AN U
HRMS [M+Na]+ m/z 437.2318 (calc. 437.2298 for C25H34NaO5).
3, 5-Diethoxybenzyl alcohol (21): A mixture of 3, 5-dihydroxybenzyl alcohol (24 g, 171.3 mmol), diethyl sulfate (55.9 mL, 428.1 mmol) and potassium carbonate anhydrous (71.0 g, 513.9 mmol) in acetone (500
TE D
mL) was refluxed under nitrogen for 18 hrs. After cooling, the solution was filtered, the cake was washed with acetone (50 mL) and the filtrate was evaporated under reduced pressure. The residue was then purified by column chromatography eluted with petroleum ether/ethyl acetate (5:1) to give
EP
3,5-Diethoxybenzyl alcohol (21) (32.7 g, 97.3%) as a colorless liquid. 1H NMR (400 MHz, CDCl3) δH: 6.51 (d, J=2.4 Hz, 2H), 6.39 (t, J=2.0, 2.4 Hz, 1H), 4.62 (s, 2H), 4.03 (q, J=6.8 Hz, 4H), 1.42 (t, J=6.8 Hz,
AC C
6H); 13C NMR (100 MHz, CDCl3) δc: 159.8, 142.8, 104.6, 100.1, 64.9, 63.0, 14.3; IR (KBr) νmax: 3442, 2980, 2930, 1597, 1456, 1393, 1292, 1171, 1115, 1059, 1032, 972, 841, 708, 689 cm-1; MS [M+H]+ m/z (%): 197.1 (100).
1-(bromomethyl)-3, 5-diethoxybenzene (22): PBr3 (15.8 mL) was added dropwise to a solution of 3, 5-diethoxybenzyl alcohol (21) (32.7 g, 166.6 mmol) and pyridine (0.67 mL, 8.3 mmol) in DCM (500 mL)
15
ACCEPTED MANUSCRIPT
at 0 oC. The mixture was stirred at room temperature for 4 hrs. Then the reaction was quenched with ice water (600 mL), extracted with DCM (2 × 300 mL), washed with brine (2 × 200 mL), dried over anhydrous Na2SO4, and concentrated to provide 1-(bromomethyl)-3, 5-diethoxybenzene (22) as a grey
RI PT
solid. (42.3g, 98.4%) The crude product can be used for next step of reaction without further purification. Mp. 53-56 oC; 1H NMR (400 MHz, CDCl3) δ: 6.54 (d, J=2.4 Hz, 2H), 6.40 (t, J=2.0, 2.4 Hz, 1H), 4.43 (s, 2H), 4.03 (q, J=6.8 Hz, 4H), 1.42 (t, J=6.8 Hz, 6H); 13C NMR (100 MHz, CDCl3) δc: 159.7, 139.1, 107.0,
SC
101.0, 63.1, 33.3, 14.3; IR (KBr) νmax: 2972, 2930, 2883, 2862, 1684, 1597, 1558, 1456, 1394, 1317, 1169,
M AN U
1113, 1057, 847, 822, 690, 550, 498 cm-1; MS [M+H]+ m/z (%): 259.1 (80).
(4a'S, 5'S, 8a'S)-5'-(3, 5-diethoxybenzyl)-5', 8a'-dimethylhexahydro-2'H-spiro [[1, 3] dioxolane-2, 1'-naphthalen]-6' (7'H)-one (23): Compound 8 (1.2 g, 5.1 mmol) in dried THF (30 mL) was added dropwise to a stirred solution of lithium (321 mg, 45.9 mmol) in liquid ammonia (50 mL) at -78 °C under
TE D
argon. The resulting solution was refluxed for 1 hrs, and then a solution of 22 (9.16 g, 35.5 mmol) in dried THF (15 mL) was added. The mixture was allowed to stand for 2 hrs at 25 °C until liquid ammonia be evaporated. Then, the saturated aqueous ammonium chloride (20 mL) was added, and the mixture was
EP
extracted with diethyl ether (3 × 30 mL). The combined organic layer was washed with brine, dried over anhydrous Na2SO4. After removal the solvent under reduced pressure, the residue was purified by column
AC C
chromatography eluted with petroleum ether/ethyl acetate (10:1) to give 23 (1.74 g, 82%) as a white foam. [α]D25+47 (c 0.03, MeOH); 1H NMR (400 MHz, CDCl3) δH: 6.31 (t, J=2.0, 2.4 Hz, 1H), 6.24 (d, J=2.0 Hz, 2H), 4.00 (q, J=6.8 Hz, 4H), 3.91-3.80 (m, 4H), 3.10 (d, J=13.6 Hz, 1H), 2.49 (d, J=13.2 Hz, 1H), 2.41-2.38 (m, 1H), 2.31-2.25 (m, 1H), 1.76-1.55 (m, 4H), 1.52-1.37 (m, 11H), 1.13 (s, 3H), 1.10 (s, 3H); 13
C NMR (100 MHz, CDCl3) δc: 216.3, 159.1, 139.9, 112.2, 108.6, 99.7, 64.6, 64.3, 62.9, 51.8, 44.5, 42.7,
41.7, 35.0, 29.7, 27.4, 22.2, 21.9, 21.8, 16.0, 14.4; IR (KBr) νmax: 2978, 2935, 2363, 1699, 1595, 1173,
16
ACCEPTED MANUSCRIPT
1059, 949, 908, 866, 820, 719, 669 cm-1; HRMS [M+Na]+ m/z 439.2459 (calc. 439.2455 for C25H36NaO5 ).
2-bromo-1-(bromomethyl)-3, 5-diethoxybenzene (24): See compound 25 for similar procedure.
RI PT
Compound 24 was obtained as a white solid in 91% yield; Mp. 107-110 oC; 1H NMR (400 MHz, CDCl3) δH: 6.62 (d, J=2.8 Hz, 1H), 6.43 (d, J=2.4 Hz, 1H), 4.60 (s, 2H), 4.08 (m, 4H), 1.50 (t, J=6.8 Hz, 3H), 1.54 (t, J=6.8, 7.2 Hz, 3H);
13
C NMR (100 MHz, CDCl3) δc: 158.5, 156.0, 137.9, 107.2, 104.8, 100.8, 64.5,
SC
63.4, 33.7, 14.3, 14.2; IR (KBr) νmax: 2982, 2934, 2885, 1603, 1582, 1456, 1391, 1331, 1184, 1117, 1074,
M AN U
1026, 889, 851, 806, 717, 660, 627 cm-1; MS [M+H]+ m/z (%) 337.0 (15).
(4a'S, 5'S, 8a'S)-5'-(2-bromo-3, 5-diethoxybenzyl)-5', 8a'-dimethylhexahydro-2'H-spiro [[1, 3] dioxolane-2, 1'-naphthalen]-6'(7'H)-one (25): To a solution of 23 (1.60 g, 3.84 mmol) in DCM (75 mL), NBS (0.72 g, 4.03 mmol) was added at 0 °C and the reaction was stirred at 0 oC for 1 hrs. The reaction mixture was
TE D
quenched with saturated aqueous NaHCO3 (15 mL). Then the mixture was diluted with H2O (30 mL), extracted with EtOAc (3 × 60 mL). The combined organic layer was then washed with brine (20 mL), dried over anhydrous MgSO4, and then concentrated under reduced pressure. The residue was purified by
EP
column chromatography eluted with petroleum ether/ethyl acetate (10:1) to give compound 25 (1.83 g, 92%) as a white foam. [α]D25 +10 (c 0.06, MeOH); 1H NMR (400 MHz, CDCl3) δH: 6.31 (d, J=2.8 Hz, 1H),
AC C
6.21 (d, J=2.4 Hz, 1H), 4.03-3.79 (m, 8H), 3.15 (d, J=14.4 Hz, 1H), 3.00 (d, J=14.0 Hz, 1H), 2.47-2.43 (m, 2H), 2.22-2.19 (m, 1H), 1.84-1.81 (m, 1H), 1.65-1.33 (m, 13H), 1.06 (s, 6H); 13C NMR (100 MHz, CDCl3) δc: 216.9, 157.6, 155.3, 138.9, 112.1, 107.7, 107.1, 99.6, 64.5, 64.4, 64.2, 63.0, 51.9, 44.3, 43.4, 41.7, 35.0, 29.4, 27.8, 22.4, 22.1, 20.6, 16.3, 14.2, 14.1; IR (KBr) νmax: 2982, 2937, 2883, 1697, 1657, 1589, 1340, 1178, 1138, 1045, 1020, 951, 806 cm-1; HRMS [M+Na]+ m/z 517.1556 (calc. 517.1560 for C25H35BrNaO5).
17
ACCEPTED MANUSCRIPT
(4aS, 5S, 11S, 12aS)-8,10-diethoxy-5, 12a-dimethyl-3, 4, 4a, 5, 6, 11, 12, 12a-octahydro-2H-spiro [5, 11-methanodibenzo [a, e] [8] annulene-1, 2'-[1, 3] dioxolan]-13-one (26): An oven-dried 100 mL
RI PT
round-bottomed flask was charged with Pd2(dba)3 (439 mg, 0.49 mmol), xant-Phos (232 mg, 0.49 mmol) and anhydrous t-BuONa (701 mg, 7.29 mmol). A solution of 25 (1200 mg, 2.43 mmol) in anhydrous dioxane (30 mL) was added under Ar, and the suspension was heated to reflux for 4 hrs. After cooling to
SC
25 °C, the reaction mixture was diluted with EtOAc (30 mL), filtered over celite, and concentrated under reduced pressure. The residue was purified by column chromatography eluted with petroleum ether/ethyl
M AN U
acetate (12:1) gave 26 (886 mg, 88%) as a pale yellow foam. 1H NMR (400 MHz, CDCl3) δH: 6.32 (s, 1H), 6.13 (s, 1H), 4.04-3.96 (m, 4H), 3.88-3.77 (m, 4H), 3.66 (d, J=9.2 Hz, 1H), 3.03 (d, J=16.4 Hz, 1H), 2.75 (d, J=16.4 Hz, 1H), 2.64-2.60 (m, 1H), 2.45 (d, J=13.6 Hz, 1H), 1.95 (t, J=9.2, 4.0 Hz, 1H), 1.14 (s, 3H), 1.00 (s, 3H); 13C NMR (100 MHz, CDCl3) δc: 220.21, 158.1, 156.5, 134.5, 123.3, 111.9, 103.9, 97.5, 64.7,
TE D
63.9, 62.9, 62.8, 48.5, 46.7, 46.2, 42.0, 41.3, 38.3, 29.1, 22.8, 22.0, 17.3, 14.42, 14.36; IR (KBr) νmax: 3367, 3337, 2980, 2934, 2883, 1717, 1178, 1134, 1072, 1022 cm-1; [α]D25+43 (c 0.075, MeOH); HRMS
EP
(ESI+): [M+Na]+ m/z 437.2303 (calc. 437.2298 for C25H34NaO5).
(4aR, 5S, 11S, 12aS)-8, 10-diethoxy-5, 12a-dimethyl-2, 3, 4, 4a, 5, 6, 12, 12a-octahydro-5,
AC C
11-ethanodibenzo [a, e] [8] annulene-1, 13(11H)-dione (27): 3.0 M hydrochloric acid (9.7 mL, 39.8 mmol) was added to a stirred solution of 26 (1.10 g, 2.66 mmol) in THF (20 mL) at 25 °C. After 2 h stirring, the reaction was quenched with saturated aqueous sodium hydrogen carbonate (6 mL), and the mixture was extracted with ethyl acetate (3 × 30 mL). The combined extracts were washed with brine (30 mL), dried over anhydrous Na2SO4, concentrated under reduced pressure afforded an oily residue, which was purified by column chromatography using petroleum ether/ethyl acetate (12:1) as elute gave 27 (905 mg, 92%) as
18
ACCEPTED MANUSCRIPT
a pale yellow solid. Mp. 147-151 oC; [α]D25+28 (c 0.05, MeOH); 1H NMR (400 MHz, CDCl3) δH: 6.29 (s, 1H), 6.09 (s, 1H), 4.03-3.93 (m, 4H), 3.73 (d, J=9.6 Hz, 1H), 3.03 (d, J=16.8 Hz, 1H), 2.76 (d, J=16.4 Hz, 1H), 2.57-2.44 (m, 3H), 2.19-2.00 (m, 1H), 1.81-1.73 (m, 2H), 1.47-1.39 (m, 7H), 1.22 (s, 3H), 1.06 (s,
RI PT
3H); 13C NMR (100 MHz, CDCl3) δc: 218.5, 213.2, 158.4, 156.6, 133.8, 122.9, 103.8, 97.4, 62.97, 62.92, 48.9, 48.1, 46.9, 46.8, 41.4, 39.8, 37.1, 24.9, 22.8, 19.3, 17.4, 14.4, 14.3; IR (KBr) νmax: 2934, 2378, 2303, 2181, 1705, 1508, 1178, 1121, 1070, 839 cm-1; HRMS [M+Na]+ m/z 393.2039 (calc. 393.2036 for
SC
C23H30NaO4).
M AN U
(4aR, 5S, 11R, 12aS)-8, 10-diethoxy-5, 12a-dimethyl-1, 13-dimethylene-1, 2, 3, 4, 4a, 5, 6, 11, 12, 12a-decahydro-5, 11-methanodibenzo [a, e] [8] annulene (28): A mixture of t-BuOK (3.75g, 33.4 mmol) and methyltriphenylphosphonium bromide (12.54g, 35.1 mmol) in dry toluene (80 mL) was refluxed at 90 o
C for 1 hr under argon. The resulted solution was cooled to 25 °C. A solution of 27 (650 mg, 1.76 mmol)
TE D
in toluene (50 mL) was added to above prepared mixture. The reactant was stirred at 90 oC for 40 hrs under argon and quenched with water (60 mL). After extracted with EtOAc (2 × 50 mL), the combined organic layer was washed with brine (30 mL), dried over anhydrous Na2SO4. After concentered under
EP
reduced pressure, the residue was purified by column chromatography eluted with petroleum ether/ethyl acetate (100:1) gave 27 (580 mg, 90%) as a pale yellow solid. Mp. 85-89 oC; [α]D25+46 (c 0.07, MeOH); H NMR (400 MHz, CDCl3) δH: 6.31 (d, J=2.0 Hz, 1 H), 6.11 (d, J=2.0 Hz, 1H), 4.93 (d, J=0.8 Hz, 1H),
AC C
1
4.82 (d, J=1.2 Hz, 1H), 4.51 (d, J=1.2 Hz, 1H); 4.08-3.91 (m, 5H), 2.81 (d, J=16.0 Hz, 1H), 2.46 (d, J=15.6 Hz, 1H), 1.81-1.73 (m, 2H), 1.47-1.39 (m, 7H), 1.22 (s, 3H), 1.06 (s, 3H);
13
C NMR (100 MHz,
CDCl3) δc: 158.6, 157.4, 155.9, 155.3, 136.4, 126.3, 104.9, 104.5, 102.9, 97.0, 62.8, 48.7, 46.6, 43.5, 39.3, 38.4, 37.4, 32.7, 26.9, 24.5, 21.9, 20.5, 14.53, 14.48; IR (KBr) νmax: 2972, 2926, 2907, 2868, 1603, 1587, 1437, 1340, 1285, 1180, 1146, 1122, 1092, 1068, 885, 839 cm-1; HRMS [M+Na]+ m/z 389.2455 (calc.
19
ACCEPTED MANUSCRIPT
389.2451 for C25H34NaO2).
(5R, 6aS, 10aR, 11S)-2-ethoxy-6a, 11-dimethyl-7, 13-dimethylene-5, 6, 6a, 7, 8, 9, 10, 10a, 11,
RI PT
12-decahydro-5, 11-methanodibenzo [a, e] [8] annulene-1, 4-dione (2): A solution of CrO3 (467 mg, 4.67 mmol) in H2O (2 mL) and AcOH (8 mL) was added drop wisely to the solution of compound 27 (450 mg, 1.23 mmol) in AcOH (12 mL) at 0 °C. The reaction mixture was stirred at room temperature and
SC
monitored by TLC (petroleum ether/EtOAc=10:1). After 30 min, ice water (20 mL) was added, and the aqueous layer was extracted with EtOAc (2 × 30 mL). The combined organic layers were washed with
M AN U
saturated NH4Cl solution (30 mL), dried over anhydrous Na2SO4. After filtration, the solution was concentration under reduced pressure. The residue was purified by column chromatography using petroleum ether/ethyl acetate (10:1) as elute to give 2 (295 mg, 68%) as a pale yellow solid. Mp. 88-93 oC; [α]D25+17 (c 0.06, MeOH); 1H NMR (400 MHz, CDCl3) δH: 5.86 (s, 1H), 4.93 (s, 1H), 4.86 (s, 1H), 4.54
TE D
(s, 1H), 4.50 (s, 1H), 4.00 (q, J=6.8 Hz, 2H), 3.77 (d, J=10.8 Hz, 1H), 2.75 (d, J=18.4 Hz, 1H), 2.22-1.95 (m, 6H), 1.83-1.79 (m, 1H), 1.70-1.67 (m, 2H), 1.56-1.43 (m, 5H), 1.24 (s, 3H), 1.09 (s, 3H);
13
C NMR
(100 MHz, CDCl3) δc: 186.2, 182.3, 157.6, 157.3, 151.5, 148.5, 138.1, 107.1, 105.6, 105.2, 64.6, 48.7,
EP
42.4, 41.6, 38.8, 37.8, 36.7, 32.6, 26.9, 24.3, 21.3, 20.2, 13.4; IR (KBr) νmax: 2930, 2860, 1717, 1647,
AC C
1219, 1111, 1034, 980, 891 cm-1; HRMS [M+Na]+ m/z 375.1937 (calc. 375.1931 for C23H28NaO3).
(5R, 6aS, 10aR, 11S)-2-ethoxy-6a, 7, 11-trimethyl-13-methylene-6, 6a, 10, 10a, 11, 12-hexahydro-5, 11-methanodibenzo [a, e] [8] annulene-1, 4(5H, 9H)-dione (1): To a solution of 2 (100 mg, 0.28 mmol) in AcOH (20 mL) was added PTSA (10 mg, 0.06 mmol), the mixture was stirred at 25 oC for 12 hrs. Then the solution was diluted with ice water (50 mL) and extracted into tert-Butyl methyl ether (3 × 20 mL). The combined extract was washed with brine (2 × 20 mL), dried over anhydrous Na2SO4 and concentrated
20
ACCEPTED MANUSCRIPT
under reduced pressure. The residue was purified by column chromatography eluted with petroleum ether/ethyl acetate (10:1) to give compound 1 (92 mg, 92%) as a pale solid. Mp = 99-102 oC; [α]D25+119 (c 0.13, MeOH); 1H NMR (400 MHz, CDCl3) δH: 5.85 (s, 1H), 5.09 (s, 1H), 4.91 (s, 1H), 4.85 (s, 1H),
RI PT
4.00 (q, J=6.8, 7.2 Hz, 2H), 3.72 (d, J=10.4 Hz, 1H), 2.79 (d, J=18.4 Hz, 1H), 2.19-2.22 (dd, J=10.4, 14.0 Hz, 1H), 2.02-1.98 (m, 1H); 1.90-1.85 (m, 1H), 1.69-1.63 (m, 2H), 1.54-1.45 (m, 8H), 1.25 (s, 3H), 1.05 (s, 3H);
13
C NMR (100 MHz, CDCl3) δc: 186.2, 182.3, 157.3, 152.0, 148.6, 142.1, 138.8, 118.9, 107.1,
SC
105.1, 64.6, 46.8, 42.4, 41.4, 37.4, 37.2, 36.6, 25.9, 19.96, 19.88, 19.3, 17.5, 13.4; IR (KBr) νmax: 2964, 2937, 1697, 1670, 1677, 1630, 1601, 1339, 1279, 1225, 1209, 1161, 1101, 1034, 889, 850 cm-1; HRMS
M AN U
[M+Na]+ m/z 375.1936 (calc. 375.1931 for C23H28NaO3 ).
(4a'S, 5'S, 8a'S)-5'-(3, 5-dimethoxybenzyl)-5', 8a'-dimethylhexahydro-2'H-spiro [[1, 3] dioxolane-2, 1'-naphthalen]-6'(7'H)-one (30): See compound 23 for similar procedure. Compound 30 was obtained as
TE D
white foam in 83% yield; [α]D25+27 (c 0.13, MeOH); 1H NMR (400 MHz, CDCl3) δH: 6.32 (t, J=2.0, 2.4 Hz, 1H), 6.26 (d, J=2.4 Hz, 1H), 3.91-3.80 (m, 4H), 3.71 (s, 6H), 3.13 (d, J=13.6 Hz, 1H); 3.72 (d, J=13.6 Hz, 1H), 2.48-2.37 (m, 1H), 2.31-2.25 (m, 2H), 1.75-1.65 (m, 3H), 1.54-1.43 (m, 5H), 1.14 (s, 3H), 1.11 13
C NMR (100 MHz, CDCl3) δc: 216.2, 159.8, 140.2, 112.1, 107.9, 98.5, 64.6, 64.3, 54.8, 51.8,
EP
(s, 3H);
44.4, 42.6, 41.7, 35.0, 29.7, 27.3, 22.2, 21.9, 21.8, 15.9; IR (KBr) νmax: 2943, 2883, 2837, 1701, 1595,
AC C
1460, 1429, 1344, 1294, 1205, 1184, 1151, 1099, 1059, 1045, 910, 829, 708 cm-1; HRMS [M+Na]+ m/z 411.2161 (calc. 411.2142 for C23H32NaO5).
(4a'S, 5'S, 8a'S)-5'-(2-bromo-3, 5-dimethoxybenzyl)-5', 8a'-dimethyl-hexahydro-2'H-spiro [(1, 3) -dioxolane-2, 1'-naphthalen]-6'(7'H)-one (31): See compound 25 for similar procedure. Compound 31 was obtained as white foam in 91% yield; [α]D25+25 (c 0.08, MeOH); 1H NMR (400 MHz, CDCl3) δH: 6.34 (d,
21
ACCEPTED MANUSCRIPT
J=2.8 Hz, 1H), 6.25 (d, J=2.8 Hz, 1H), 3.89-3.79 (m, 7H), 3.73 (s, 3H), 3.18 (d, J=13.2 Hz, 1H), 3.03 (d, J=14.0 Hz, 1H), 2.49-2.43 (m, 2H), 2.23-2.19 (m, 1H), 1.84-1.82 (m, 1H), 1.77-1.41 (m, 7H), 1.09 (s, 3H), 1.08 (s, 3H); 13C NMR (100 MHz, CDCl3) δc: 217.2, 158.4, 155.9, 139.2, 112.2, 107.0, 103.7, 97.9, 64.6,
RI PT
64.3, 55.8, 54.9, 52.1, 44.3, 43.4, 41.8, 35.1, 29.5, 27.8, 22.4, 22.2, 20.8, 16.3; IR (KBr) νmax: 2937, 2881, 2856, 1701, 1591, 1458, 1437, 1381, 1340, 1288, 1202, 1163, 1082, 1022, 949, 910 cm-1; HRMS
SC
[M+Na]+ m/z 489.1259 (calc. 489.1247 for C23H31BrNaO5).
(4aS, 5S, 11S, 12aS)-8, 10-dimethoxy-5, 12a-dimethyl-3, 4, 4a, 5, 6, 11, 12, 12a-octahydro-2H-spiro [5,
M AN U
11-methanodibenzo [a, e] [8] annulene-1, 2'-[1, 3] dioxolan]-13-one (32): In a sealed tube was charged with Pd(OAc)2 (225 mg, 1.0 mmol), PPh3 (262 mg, 1.0 mmol) and Cs2CO3 (3257 mg, 9.99 mmol), a solution of 31 (1550 mg, 3.33 mmol) in anhydrous THF (60 mL) was added, the resulting suspension was heated to 100 oC for 24 hrs. After cooling to 25 °C, the reaction mixture was diluted with EtOAc (30 mL),
TE D
filtered through celite and then concentrated under vacuum. The residue was purified by column chromatography eluted with petroleum ether/ethyl acetate (10:1) gave 32 (1093 mg, 85%) as a white foam. [α]D25+84 (c 0.05, MeOH); 1H NMR (400 MHz, CDCl3) δH: 6.34 (d, J=2.0 Hz, 1H), 6.15 (d, J=2.0 Hz,
EP
1H), 3.89-3.87 (m, 3H), 3.80-3.78 (m, 7H), 3.65 (d, J=9.2 Hz, 1H), 3.05 (d, J=16.4 Hz, 1H), 2.71 (d, J=16.4 Hz, 1H), 2.63 (dd, J=4.8, 12.0 Hz, 1H), 2.42 (d, J=13.6 Hz, 1H), 1.95 (dd, J=9.2, 13.6 Hz, 1H),
AC C
1.67-1.33 (m, 7H), 1.15 (s, 3H), 1.00 (s, 3H); 13C NMR (100 MHz, CDCl3) δc: 219.9, 158.8, 157.4, 134.6, 123.4, 111.8, 103.4, 96.5, 64.7, 63.9, 54.9, 54.7, 48.5, 46.7, 46.2, 41.9, 41.3, 38.4, 29.0, 22.8, 21.9, 17.3; IR (KBr) νmax: 3431, 2976, 2937, 1717, 1609, 1589, 1458, 1339, 1209, 1132, 1074, 1053, 1018, 939, 825 cm-1; HRMS [M+Na]+ m/z 409.1994 (calc. 409.1985 for C23H30NaO5).
(4aR, 5S, 11S, 12aS)-8, 10-dimethoxy-5, 12a-dimethyl-2, 3, 4, 4a, 5, 6, 12, 12a-octahydro-5,
22
ACCEPTED MANUSCRIPT
11-methanodibenzo [a, e] [8] annulene-1, 13(11H)-dione (33): See compound 27 for similar procedure. Compound 33 was obtained as white solid in 93% yield; Mp. 138−143 oC; [α]D25+37 (c 0.07, MeOH); 1H NMR (400 MHz, CDCl3) δH: 6.33 (d, J=2.0 Hz, 1H), 6.13 (d, J=1.6 Hz, 1H), 3.81(s, 3H), 3.77 (s, 3H),
3H), 1.85-1.76 (m, 2H), 1.53-1.43 (m, 1H), 1.25 (s, 3H), 1.09 (s, 3H);
RI PT
3.72 (d, J=9.6 Hz, 1H), 3.06 (d, J=16.4 Hz, 1H), 2.81 (d, J=16.4 Hz, 1H), 2.59-2.47 (m, 3H), 2.22-2.02 (m, 13
C NMR (100 MHz, CDCl3) δc:
218.2, 213.3, 159.1, 157.3, 133.9, 123.0, 103.3, 96.3, 54.9, 54.8, 48.9, 48.1, 46.98, 46.88, 41.3, 39.8, 37.1,
SC
24.9, 22.8, 19.4, 17.4; IR (KBr) νmax: 3475, 2939, 2899, 1705, 1605, 1593, 1489, 1458, 1356, 1207, 1145,
M AN U
1120, 1053, 976 928, 831 cm-1; HRMS [M+Na]+ m/z 365.1732 (calc. 365.1723 for C21H26NaO4).
(4aR, 5S, 11R, 12aS)-8, 10-dimethoxy-5, 12a-dimethyl-1, 13-dimethylene-1, 2, 3, 4, 4a, 5, 6, 11, 12, 12a-decahydro-5, 11-ethanodibenzo [a, e] [8] annulene (34): See compound 28 for similar procedure. Compound 34 was obtained as white solid in 92% yield; Mp. 81−86 oC; [α]D25+66 (c 0.085, MeOH); 1H
TE D
NMR (400 MHz, CDCl3) δH: 6.32 (d, J=2.0 Hz, 1H), 6.13 (d, J=2.0 Hz, 1H), 4.92 (d, J=0.8 Hz, 1H), 4.81 (d, J=1.2 Hz, 1H), 4.51 (d, J=1.6 Hz, 1H), 3.90 (dd, J=5.2, 5.6 Hz, 1H), 3.84 (s, 3H), 3.77 (s, 3H), 2.82 (d, J=16.0 Hz, 1H), 2.46 (d, J=16.0 Hz, 1H), 2.27-2.20 (m, 1H), 2.11-2.05 (m, 3H), 1.80-1.54 (m, 3H), 1.23 13
C NMR (100 MHz, CDCl3) δc: 158.5, 158.1, 156.6, 155.1, 136.5, 126.1, 105.1,
EP
(s, 3H), 1.13 (s, 3H);
103.9, 102.9, 95.9, 54.9, 54.8, 48.7, 46.7, 43.5, 39.3, 38.4, 37.3, 32.7, 26.9, 24.5, 21.9, 20.5; IR (KBr) νmax:
AC C
2989, 2930, 2854, 1630, 1605, 1593, 1487, 1458, 1354, 1213, 1196, 1088, 1122, 879, 827, 770, 629 cm-1; HRMS [M+Na]+ m/z 361.2143 (calc. 361.2138 for C23H30NaO2).
(5R, 6aS, 10aR, 11S)-2-methoxy-6a, 11-dimethyl-7, 13-dimethylene-5, 6, 6a, 7, 8, 9, 10, 10a, 11, 12-decahydro-5, 11-methanodibenzo [a, e] [8] annulene-1, 4-dione (3): See compound 2 for similar procedure. Compound 3 was obtained as light yellow solid in 67% yield; Mp. 86-91 oC; [α]D25+19 (c
23
ACCEPTED MANUSCRIPT
0.075, MeOH); 1H NMR (400 MHz, CDCl3) δH: 5.89 (s, 1H), 4.94 (s, 1H), 4.87 (s, 1H), 4.56 (s, 1H), 4.51 (s, 1H), 3.81 (s, 3H), 3.77 (s, 3H), 2.82 (d, J=16.0 Hz, 1H), 2.46 (d, J=16.0 Hz, 1H), 2.27-2.20 (m, 1H), 2.11-2.05 (m, 3H), 1.80-1.54 (m, 3H), 1.23 (s, 3H), 1.13 (s, 3H); 13C NMR (100 MHz, CDCl3) δc: 185.9,
RI PT
182.2, 158.1, 157.6, 151.4, 148.7, 138.2, 106.9, 105.6, 105.3, 55.7, 48.8, 42.4, 41.6, 38.8, 37.8, 36.8, 32.6, 26.9, 24.4, 21.3, 20.2; IR (KBr) νmax: 2964, 2926, 2877, 1697, 1670, 1647, 1602, 1558, 1458, 1231, 1221,
SC
1030, 885, 851, 775 cm-1; HRMS [M+Na]+ m/z 361.1781 (calc. 361.1774 for C22H26NaO3).
(5R, 6aS, 10aR, 11S)-2-methoxy-6a, 7, 11-trimethyl-13-methylene-6, 6a, 10, 10a, 11, 12-hexahydro-5,
M AN U
11-methanodibenzo [a, e] [8] annulene-1, 4(5H, 9H)-dione (4): See compound 1 for similar procedure. Compound 4 was obtained as light yellow solid in 90% yield; Mp. 95−98 oC; [α]D25+129 (c 0.085, MeOH); 1
H NMR (400 MHz, CDCl3) δH: 5.88 (s, 1H), 5.09 (d, J=3.2 Hz, 1H), 4.92 (s, 1H), 4.86 (s, 1H), 3.81 (s,
3H), 3.73 (d, J=10.4 Hz, 1H), 2.80 (d, J=18.8 Hz, 1H), 2.20 (dd, J=10.4, 13.6 Hz, 1H), 2.04 (d, J=18.4 Hz,
TE D
2H), 1.90-1.86 (m, 1H), 1.70-1.66 (m, 2H), 1.55-1.49 (m, 5H), 1.26 (s, 3H), 1.06 (s, 3H); 13C NMR (100 MHz, CDCl3) δC: 185.9, 182.2, 158.1, 157.6, 151.4, 148.7, 138.2, 106.9, 105.6, 105.3, 55.7, 48.8, 42.4, 41.6, 38.8, 37.8, 36.8, 32.6, 26.9, 24.4, 21.3, 20.2; IR(KBr) νmax: 2959, 2935, 1697, 1670, 1647, 1602,
EP
1558, 1375, 1340, 1229, 1211, 1099, 1026, 1005, 887, 845 cm-1; HRMS [M+Na]+ m/z 361.1786 (calc.
AC C
361.1774 for C22H26NaO3).
IC50 Value Determination for Human Kidney Carcinoma Cell lines 786-O and Human Prostate Cancer Cell lines PC-3. Human kidney carcinoma cells 786-O and human prostate cancer cells PC-3 were inoculated into 96 well microtiter plates at 10,000 and 7,500 cells/well in RPMI-1640 and DMEM/F12 medium containing 5% fetal bovine serum. After cell inoculation, the microtiter plates are incubated at 37° C, 5% CO2, 95% air and 100% relative humidity for 24 hrs prior to addition of experimental drugs.
24
ACCEPTED MANUSCRIPT
After 24 hrs, two plates of each cell line are fixed in situ with TCA, to represent a measurement of the cell population for each cell line at the time of compounds addition. At the time of compounds addition, different compounds dilutions are added to the appropriate microtiter wells already resulting in the
RI PT
required final drug concentrations. Following compounds addition, the plates are incubated for an additional 48 hrs at 37 °C, 5% CO2, 95% air, and 100% relative humidity. Cells are fixed in situ by cold 50% (w/v) TCA and incubated for 1 hr at 4 °C. The plates are washed five times with water and air dried.
SC
Sulforhodamine B (SRB) solution (100 µL) at 0.4% (w/v) in 1% acetic acid is added to each well, and plates are incubated for 10 minutes at room temperature. After staining, unbound dye is removed by
M AN U
washing five times with 1% acetic acid and the plates are air dried. Bound stain is subsequently solubilized with 10 mM trizma base, and the absorbance is read on an automated plate reader at a wavelength of 515 nm.
TE D
Acknowledgment
This research was supported by Science & Technology Commission of Shanghai municipality (grant number: 14401900600) and Jiangsu municipal government (333 high level talent funding project, grant
EP
number: BRA2013081). The authors would like to thank Miss. Runzhong Fu from University of South California, U.S.A for a very helpful linguistic modification. The authors also appreciate the help provided
AC C
by Prof. Peilan He from Shanghai Institute of Material Medica, Chinese Academy of Sciences and Dr. Yibo Wang from Basilea Pharmaceutica China Ltd.
References
(1) Faulkner, D. J. Nat. Prod. Rep. 1996, 13, 75-125. (2) An, J. G.; Wiemer, D. F. J. Org. Chem. 1996, 61, 8775-8779.
25
ACCEPTED MANUSCRIPT
(3) Ciavatta, M. L.; Lopez Gresa, M. P.; Gavagnin, M.; Romero, V.; Melck, D.; Manzo, E.; Guo, Y. W.; Van Soest, R.; Cimino, G. Tetrahedron 2007, 63, 1380-1384. (4) Mcnamara, C. E.; Larsen, L.; Perry, N. B.; Harper, J. L.; Berridge, M. V.; Chia, E. W.; Kelly, M.;
RI PT
Webb, V. L. J. Nat. Prod. 2005, 68, 1431-1433.
(5) (a) Jiao, W. H.; Huang, X. J.; Yang, J. S.; Yang, F.; Piao, S. J.; Gao, H.; Li, J.; Ye, W. C.; Yao, X. S.; Chen, W. S.; Lin, H. W. Org. Lett. 2012, 14, 202-205. (b) Jiao, W. H.; Xu, T. T.; Yu, H. B.; Chen, G.
SC
D.; Huang, X. J.; Yang, F.; Li, Y. S.; Han, B. N.; Liu, X. Y.; Lin, H. W. J. Nat. Prod. 2014, 77, 346-350.
M AN U
(6) (a) Schmalzbauer, B.; Herrmann, J.; Müller, R.; Menche, D. Org. Lett. 2013, 15, 964-967. (b) Fukui, Y.; Narita, K.; Katoh, T. Chem. Eur. J. 2014, 20, 2436-2439.
(7) (a) Smith III, A. B.; Mewshar, R. J. Org. Chem. 1984, 49, 3685-3689. (b) Corey, E. J.; Roberts, B. E. J. Am. Chem. Soc. 1997, 119, 12425-12431. (c) Petra, S.; Herbert, W. Angew. Chem. 1999, 111,
TE D
3935-3938. (d) Ling, T.; Rivas, F.; Theodorakis, E. A. Tetrahedron Lett. 2002, 43, 9019-9022. (e) Junji, S.; Takuya, K.; Kazuhiro, W.; Tadashi, K.; Ohgi, T. Eur. J. Org. Chem. 2011, 16, 2948-2957. (8) (a) Hagiwara, H.; Uda, H. J. Org. Chem. 1988, 53, 2308-2311. (b) Ling, T.; Xu, J.; Smith, R.;
EP
Theodorakis, E. A.; Ali, A.; Cantrell, C. L. Tetrahedron 2011, 67, 3023-3029. (c) Takahashi, S.; Oritani, T.; Yamashita, K. Tetrahedron 1988, 44, 7081-7088. (d) Ling, T.; Poupon, E.; Rueden, E. J.;
AC C
Kim, S. H.; Theodorakis, E. A. J. Am. Chem. Soc. 2002, 124, 12261-12267. (e) Cheung, A. K.; Murelli, R.; Snapper, M. L. J. Org. Chem. 2004, 69, 5712-5719. (f) Patent: Koch, M. A.; Odermatt, A.; Waldmann, H.; Scheck, M. WO 200669787, 2006 [Chem. Abstr. 2006, 145, 124765]. (g) Pereira, A. R.; Strangman, W. K.; Marion, F.; Feldberg, L.; Roll, D.; Mallon, R.; Hollander, I.; Andersen, R. J. J. Med. Chem. 2010, 53, 8523-8533. (h) Scheck, M.; Koch, M. A.; Waldmann, H. Tetrahedron 2008, 64, 4792-4802.
26
ACCEPTED MANUSCRIPT
(9) (a) Stahl, P.; Waldmann, H. Angew. Chem. Int. Ed. 1999, 38, 3710-3713. (b) Poigny, S.; Guyot, M.; Samadi, M. J. Org. Chem. 1998, 63, 5890-5894. (c) Stahl, P.; Kissau, L.; Mazitschek, R.; Huwe, A.; Furet, P.; Giannis, A.; Waldmann, H. J. Am. Chem. Soc. 2001, 123, 11586-11593. (d) Bruner, S. D.;
RI PT
Radeke, H. S.; Tallarico, J. A.; Snapper, M. L. J. Org. Chem. 1995, 60, 1114-1115. (e) Fretz, S. J.; Hadad, C. M.; Hart, D. J.; Vyas, S.; Yang, D. J. Org. Chem. 2013, 78, 83-92. (f) Snitman, D. L.; Tsai, M. Y.; Watt, D. S. J. Org. Chem. 1979, 44, 2838-2842.
SC
(10) Locke, E. P.; Hecht, S. M. Chem. Commun. 1996, 2717-2718.
(11) (a) Lanfranchi, D. A.; Hanquet, G. J. Org. Chem. 2006, 71, 4854-4861. (b) Ali, M. H.; Niedbalski, M.;
M AN U
Bohnert, G.; Bryant, D. Syn. Commun. 2006, 36, 1751-1759. (c) Yamazaki, S. Tetrahedron Lett. 2001, 42, 3355-3358. (d) Bissel, P.; Nazih, A.; Sablong, R.; Lepoittevin, J. P. Org. Lett. 1999, 1, 1283-1285. (12) (a) Bradshaw, B.; Etxebarria-Jardi, G.; Bonjoch, J. Org. Biomol. Chem. 2008, 6, 772-. (b) Chaudhury,
AC C
EP
TE D
S.; Li, S.; Donaldson, W. A. Chem. Commun. 2006, 19, 2069-2070.
27
ACCEPTED MANUSCRIPT
Total Synthesis of Dysidavarone A
7 Steps, 34% overall yield
O
+ O
O
EtO
OEt
H
SC
Br
RI PT
Chunhui Yu, Xiaoguang Zhang, Jinghua Zhang and Zhengwu Shen*
O
OEt
O
AC C
EP
TE D
M AN U
Dysidavarone A
S0040-4020(16)30490-2
DOI:
10.1016/j.tet.2016.05.073
Reference:
TET 27800
To appear in:
Tetrahedron
Received Date: 15 April 2016 Revised Date:
24 May 2016
Accepted Date: 30 May 2016
Please cite this article as: Yu C, Zhang X, Zhang J, Shen Z, Total synthesis of dysidavarone A, Tetrahedron (2016), doi: 10.1016/j.tet.2016.05.073. This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
ACCEPTED MANUSCRIPT
Total Synthesis of Dysidavarone A
†
School of Medicine, Shanghai Jiao Tong University, Shanghai 200025, People’s Republic of China
Shanghai University of Traditional Chinese Medicine, Shanghai 201203, People’s Republic of China
M AN U
SC
‡
RI PT
Chunhui Yu#, ‡, Xiaoguang Zhang #, ‡, Jinghua Zhang#,† and Zhengwu Shen*,†
ABSTRACT. Dysidavarone A is a sesquiterpene isolated from the South China Sea sponge Dysidea avara and was reported that it showed significant anticancer activities. Because the compound has unique “dysidavarane” carbon skeleton and potent biological activity, a seven-step stereoselective synthesis of dysidavarone A was developed. The key steps of the synthesis involved stereoselective intramolecular
α-arylation
TE D
reductive-alkylation,
and
double
bond
migration
reaction.
The
anti-proliferation activities of Dysidavarone A against human kidney carcinoma cell lines 786-O and
EP
human prostate cancer cell lines PC-3 were also assessed.
AC C
During the past three decades, many natural products containing quinone or hydroquinone skeleton have been isolated from marine sponges.1,2 Most of those compounds were reported to have interesting biological activities including antibacterial, antitumor, antifungal and anti-inflammatory activities.3,4 Dysidavarone A is one of the quinone sesquiterpene isolated from the South China Sea sponge Dysidea
*
#
To whom correspondence should be addressed. Tel:+86-21-64457997. E-mail: [email protected]. These authors contributed equally to the paper.
1
ACCEPTED MANUSCRIPT
avara. The compound was reported to have potent antiproliferation activities against four human cancer cell lines.5 Due to its unique three-dimensional architecture of tetracyclic core and promising biological activity, dysidavarone A has become thetarget of synthetic laboratories. So far, there are two groups who
RI PT
have completed the total synthesis of dysidavarone A.6 Herein, we report our studies of the total synthesis of dysidavarone A from a commercial available starting material 2-methyl cyclohexanone-1, 3-dione. Although our synthetic strategy was similar to the Menche’s synthesis6a, the use of less steric hindered 3,
SC
5-diethoxyl benzyl bromide 22 as the alkylation agent, not only improved the yield of reductive alkylation reaction, but also circumvented the deprotection step through direct oxidization of the phenol moiety into
M AN U
quinone (2). Hence the overall yield of the synthesis was significantly improved. In addition, the antiproliferation activities of dysidavarone A and its derivatives (Figure 1) against human kidney
AC C
EP
TE D
carcinoma cells 786-O and human prostate cancer cells PC-3 were also presented.
.
Figure 1. Dysidavarone A and its derivatives
RESULTS AND DISCUSSION Our initial retrosynthetic analysis of dysidavarone A is outlined in Scheme 1. The two double bonds of Dysidavarone A can be easily obtained from the Wittig olefination of 4, 8-diketone of compound 5 with
2
ACCEPTED MANUSCRIPT
the subsequent double bond isomerization. The quinone moiety of the dysidavarone A can be derived from the aromatic ring of compound 5. The compound 5 was envisioned to be synthesized through the alpha arylation reaction from compound 6. The strategy used for appending the aromatic moiety to the bicyclic
RI PT
sesquiterpene skeleton is well documented 7 and is based upon the stereoselective reductive alkylating of an enone derivative 8 with a substituted benzyl bromide. The Wieland-Miescher ketone analogue 8 could
SC
be readily obtained from 2-methylcyclohexane-1, 3-dione in three steps.8
O
H
OEt
H
OEt
M AN U
OEt
O
O
O
Dysidavarone A (1)
H
O
OEt
OEt
OEt
O O Br
Br
TE D
O
OEt
Br
OEt
6
OEt
5
OEt 7
+ O
O 8
EP
Scheme 1. Retrosynthetic Analysis of Dysidavarone A
Based on above retrosynthetic analysis, our initial synthetic approach started from the preparation of
AC C
compound 7 and compound 8. As illustrated in Scheme 2, the Wieland-Miescher ketone analogue 8 was prepared smoothly from commercially available 2-methyl cyclohexanone-1,3-dione 9 in three steps with 93.2% ee according to a previously reported procedure.8 The substituted benzyl bromide 7 was obtained from orcinol in five steps with 61.8% overall yield. The key reactions used for the synthesis of compound 7 involving Vilsmeier-Haack reaction, Baeyer-Villiger oxidation and double-bromination with NBS.
3
ACCEPTED MANUSCRIPT
9
O L-phenylalanine (+)-CSA/DMF rt to 70 oC 85%
O
O
Et2(SO4)2
OH 12
Et2(SO4)2
OEt EtO
K2 CO3, Acetone 10 h 96%
90%
O
O
11
H2O2-KHSO4 EtO
DMF, 100 oC, 1 h OEt 13
MeOH rt, 4 h OEt O
91%
14 OEt
3.2 eq NBS EtO
Br
hv, CCl4, 6 h
O 8
POCl3 EtO
EtO
K2CO3, Acetone 18 h 97%
O
DCM, rt, 48 h
10
HO
TsOH, MEG
RI PT
TEA, EtOAC 70 oC, 10 h 94%
O
O
90%
OH
OEt 15
SC
O ethyl vinyl ketone
Br 81%
OEt 7
M AN U
OEt 16
Scheme 2. The Synthesis of Compound 7 and 8
Having the compound 7 and compound 8 in hand, as illustrated in Scheme 3, we began to explore the
TE D
reductive alkylation reaction and try to synthesize the key intermediate 6. However, despite of various reaction conditions screened,9 the yield of the reaction is very poor, only small amounts of compound 6 was obtained (8%). Although, the compound 6 can be converted into 18 in 72% yield, the exceptional low
EP
yield of 6 prompted us to focus our investigation on the reductive alkylation reaction.
The stepwise
approach of this reaction was examined, the stereoselective Birch reduction of compound 7 went on
AC C
smoothly and gave the ketone 17 as a single isomer in 89% yield. However, the subsequent alkylation reaction was not successful even under vigorous reaction condition.
4
ACCEPTED MANUSCRIPT
Li, NH3, THF, -78 oC to -33 oC, 7, 8%
o
7
O
-78 C to -33 C O
89%
O 8
various conditions
O O Br 6
17 OEt
H
O
2h 88%
OEt
OEt
H
OEt 3N HCl, THF O
O
O
OEt O
O
OEt 5
18 OEt
H
O
H
OEt
OEt
M AN U
OEt
Pd(OAc)2, PPh3 OEt THF, 100 oC, 24 h 72%
SC
O
OEt
H
O
o
RI PT
H
O Li, NH3,THF
O
OEt
Dysidavarone A
19
Scheme 3. The Initiate Synthetic Approach
TE D
We anticipated that the low efficiency of the alkylation is due to the steric hindrance of the ortho-substitutions on the aromatic ring of the benzyl bromide.7 Hence, the less steric hindrance alkylating agent, 3, 5-diethoxyl benzyl bromide 22 was selected as the alkylation agent for the reaction (Scheme 4).
EP
The 3, 5-diethoxyl benzyl bromide 22 was readily synthesized from compound 20 in two steps quantitatively. The reaction between compound 8 and compound 22 went on smoothly and the key
AC C
intermediate 23 was obtained in 82% yield under standard reductive-alkylation condition. Since compound 8 has 5β-Me configuration (Scheme 5), the initial stereoselective hydride SN2 addition at position 10 and the sequent alkylation occurred from the less hindered α-face of the anion intermediate to form compound 23 stereoselectively (dr>19:1). The stereochemistry of 23 was confirmed by two-dimensional NMR spectroscopic methods. The dibromo-substituted compound 24 could also be used as the alkylation agent in the reductive alkylation reaction and the compound 25 was obtained in 60% yield. These results indicated that the size of the substituent at the ortho position of benzyl bromide is the
5
ACCEPTED MANUSCRIPT
main factor which affect the yield of this reaction. The bromination of compound 23 with NBS in methylene chloride gave the compound 25 as the only product in 92% yield. EtO Et2(SO4)2
OEt PBr3, Py
EtO
OEt
OH 21
20
98%
NBS DCM, 0 oC, 1 h 92%
SC
8 OEt Li, NH3,THF OEt
tBuONa, Diox 100 oC, 4 h 88%
O O
O
OEt
OEt 28
O
OEt O Br OEt
25
Ph3PCH3Br
OEt
tBuOK, toulene 40 h 90%
O
92%
OEt
27
CrO3
O
H
OEt
AcOH, H2 O 0 oC, 0.5 h 68%
TE D
OEt
H
3N HCl, THF 2h
26
H
M AN U
OEt
x-phos, Pd2(dba)3
H
O
60%
24
H
O
-78 oC to -33 oC
Br
OEt
23
NBS DCM, 0 oC, 1 h 91%
Br
OEt
O O
82%
Br 22
H
O
-78 oC to -33 o C
DCM, rt, 4 h
K2CO3, Acetone 18 h 97% OH
8 Li, NH3,THF
RI PT
OH
HO
2
p-TsOH
H
O OEt
AcOH, rt, 12 h O
92%
O Dysidavarone A
EP
Scheme 4. The Total Synthesis of Dysidavarone A
AC C
The palladium catalyzed intra-molecular cyclization of compound 25 gave the tetracyclic core of the dysidavarone A in a stereospecific manner in 88% yield. The dioxolane protecting group of compound 26 was removed in the presence of 3N hydrochloric acid in 92% yield and a subsequent Wittig reaction formed two exocyclic double bonds in one step in 90% of yield.10 The key step for accomplishing the synthesis is to convert the aromatic ring into quinone moiety without affecting the allylic positions of two exocyclic double bonds. Due to the substitution pattern on the aromatic ring of compound 28, compound 2 was expected as the only product of oxidation. Various oxidants including CAN, salcomine and CrO3
6
ACCEPTED MANUSCRIPT
were screened. Finally, the CrO3 was selected as which successfully accomplished the desired oxidation and gave compound 2 in 68% yield.11 The final step for the synthesis of dysidavarone A is to convert the exocyclic double bond at position 4 of compound 2 into endo-double bond. Again, various acids and
RI PT
Lewis acids were investigated which includes RuCl3, RhCl3.3H2O, PTSA, TFA and HCl. Eventually, PTSA in AcOH was found to be the best conditions for such double bond migrate reaction, and compound
+e
O
O
O
O
O
.
.
Protonation
M AN U
8
- .
Li, NH3
SC
2 was successfully converted into dysidavarone A in 90% yield.12
O
O
8b
8a
OH
O 8c
X R
OH
-
H
O
23
+e
O
O
O
TE D
O
8d
8e
EP
Scheme 5. The Stereochemistry of Reductive Alkylation
The synthetic dysidavarone A obtained is identical in all respects (NMR, IR, and MS) to natural
AC C
dysidavarone A. The total synthesis of dysidavarone A described above requires seven steps from readily available diketone 8 and proceeds in 34% overall yield. Upon we were finishing this synthesis, Menche’s group published the first total synthesis of dysidavarone A with a similar strategy. Compared with Menche’s synthesis, this synthesis used a less steric hindered 3, 5-diethoxyl benzyl bromide 22 as the alkylation agents, not only improved the yield of reductive alkylation, but also omitted the deprotection step through direct oxidize the phenol moiety into quinone. The methyl derivative 4 was also obtained according the same procedure from compound 8 in seven steps in 33% overall yield (Scheme 6).
7
ACCEPTED MANUSCRIPT
O Li, NH3,THF -78 oC to -33 oC OMe 83% 29
H
H
O
8
H
OMe
OMe
90%
3
M AN U
AcOH, rt, 12 h O
OMe
SC
O
H
O
32
CrO3 0 oC, 0.5 h AcOH, H2O 67%
p-TsOH
OMe
O
O
OMe 33
Pd(OAc)2, PPh3 THF, 100 o C, 24 h
H
2 h, 93%
O
OMe
OMe
3N HCl, THF
O
34
O
O Br 31 85%
tBuOK, toulene 40 h, 92% OMe
OMe
O
91%
OMe
30
H
O
DCM, 0 oC, 1 h
O
OMe Ph3PCH3Br
H
NBS
OMe
RI PT
OMe
Br
O
4
Scheme 6. The synthesis of methyl derivative of Dysidavarone A
TE D
The compounds synthesized above were assessed for the anti-proliferation activities against renal cancer cell lines 786-O and prostate cancer cell lines PC-3. The GI50 of the compounds were listed in
Conclusions
EP
Table 1. All these four compounds tested showed moderate anti-proliferation activities.
AC C
In conclusion, dysidavarone A was successfully synthesized in seven steps starting from known building block 8. Compared with Menche’s approach, this synthesis used a less steric hindered 3, 5-diethoxyl benzyl bromide 22 as the alkylation agents, not only improved the yield of reductive alkylation, but also omitted the deprotection step through direct oxidize the phenole moiety into quinone, thus the overall yield of the synthesis was significantly improved.
8
ACCEPTED MANUSCRIPT
Table 1 The Anti-proliferation Activities of dysidavarone A and Its Derivatives 786-Oa GI50
PC-3b GI50
Compound (µM)
Dysidavarone A (1)
3.71
6.71
2
6.12
3
6.37
4
3.58
7.19
7.05 5.61
SC
<0.02
Taxol
<0.02
786-O (Human kidney carcinoma cells). b
M AN U
a
RI PT
(µM)
PC-3 (Human prostate cancer cells).
Experimental Section
TE D
General Experimental Procedures. Optical rotation was measured with a Perkin-Elmer 341 MC polarimeter. HR-EIMS spectra were obtained with a Q-TOF Micro LC-MS-MS spectrometer, and ESI-MS spectra with an Agilent 1100 1946 DLC-MS spectrometer. NMR spectra were acquired on a
EP
Varian INOVA 400 MHz and Bruker AM-400 spectrometer with TMS as the internal standard. Data are reported as follows: chemical shift, multiplicity (s = singlet, d = doublet, t = triplet, dd = doublet of
AC C
doublet, b = broad, q = quartet, m = multiplet). Infrared spectra were measured using film KBr pellet techniques and were acquired using a Shimadzu FTIR-8400S spectrometer. Column chromatography (CC) separations were carried out using silica gel H60 (300-400 mesh, Qingdao Haiyang Chemical Group Corp.). 786-O and PC-3 cells were obtained from Shanghai Institute of Material Medica of Chinese Academy of Sciences and were grown in RPMI-1640 and DMEM/F12 medium containing 5% fetal bovine serum.
9
ACCEPTED MANUSCRIPT
2-methyl-2-(3-oxopentyl)cyclohexane-1, 3-dione (10): To a solution of 2-methyl-1, 3-cyclohexadione (9) (3.6 g, 28.7 mmol) in ethyl acetate (200 mL) were added triethylamine (5.2 mL, 37.3 mmol) and ethyl
RI PT
vinyl ketone (3.1 mL, 31.2 mmol). The reaction mixture was heated at 70 °C for 10 hrs and then cooled to 25 °C. The solvent was removed under reduced pressure and the residue was purified by column chromatography eluted with petroleum ether/ethyl acetate (1:2) to give triketone 10 (5.74 g, 94%) as a
SC
pink oil. 1H NMR (400 MHz, CDCl3) δH: 2.76-2.68 (m, 2H), 2.65-2.57 (m, 2H), 2.40 (t, J=7.2 Hz, 1H), 2.32-2.28 (t, J=7.2, 7.6 Hz, 2H), 2.08-1.99 (m, 3H), 1.94-1.84 (m, 1H), 1.22 (s, 3H), 1.02 (t, J=8.0 Hz,
M AN U
3H); 13C NMR (100 MHz, CDCl3) δc: 209.8, 209.6, 63.9, 37.3, 36.5, 35.5, 29.3, 19.3, 17.1, 7.2. IR (KBr) νmax: 2976, 2939, 1716, 1686, 1458, 1375, 1364, 1340, 1319, 1115, 1026 cm-1; MS [M+H]+ m/z (%): 211.2 (80).
TE D
(S)-5, 8a-dimethyl-3, 4, 8, 8a-tetrahydronaphthalene-1, 6 (2H, 7H)-dione (11): A solution of the triketone 10 (2.9 g, 13.6 mmol), L-α-phenylalanine (2.26 g, 13.6 mmol) and D-camphorsulfonic acid (1.58 g, 6.8 mmol) in DMF (30 mL) was stirred at 25 °C under argon atmosphere overnight. The mixture was then
EP
heated at 30 °C for 24 hrs, and the temperature was raised in 10 °C intervals every 24 hrs in 4 days. Then the mixture was stirred at 70 °C for additional 24 hrs. The reactant was poured into cold 5% aqueous
AC C
solution of NaHCO3 (100 mL), extracted with ethyl ether (2 × 60 mL), then dried over anhydrous Na2SO4. After removal solvent under reduced pressure, the residue was purified by column chromatography eluted with petroleum ether/ethyl acetate (1:3) to give enone 11 (2.22 g, 85%) as a light yellow oil. [α]D25+132 (c 0.85, CHCl3); 1H NMR (400 MHz, CDCl3) δH: 2.88-2.82 (m, 1H), 2.67-2.63 (m, 1H), 2.53-2.39 (m, 4H), 2.16-2.03 (m, 3H), 1.80 (s, 3H), 1.78-1.74 (m, 1H), 1.41 (s, 3H); 13C NMR (100 MHz, CDCl3) δc: 212.3, 197.9, 158.4, 130.9, 50.9, 37.6, 33.5, 29.8, 27.5, 23.6, 21.7, 11.5. IR (KBr) νmax: 2974, 2943, 1709, 1647,
10
ACCEPTED MANUSCRIPT
1635, 1448, 1420, 1375, 1362, 1317, 1167, 1026 cm-1; MS [M+H]+ m/z (%): 193.2 (100).
(S)-5', 8a'-dimethyl-3', 4', 8', 8a'-tetrahydro-2'H-spiro{[1, 3]dioxolane-2, 1'-naphthalen}-6'(7'H)-one (8):
RI PT
To a solution of compound 11 (1.75 g, 9.1 mmol) in DCM (17 mL), 2-ethyl-2-methyl-3-dioxolane (17 mL), ethylene glycol (60 mg, 0.9 mmol) and p-toluenesulfonic acid (180 mg, 0.9 mmol) were added. The solution was stirred at 25 °C for 48 hrs, and then the mixture of triethylamine (1 mL) in DCM (60 mL)
SC
were added. The organic phase was washed with saturated aqueous NaCl solution and dried over anhydrous Na2SO4. The solvent was removed under reduced pressure and the residue was purified by
M AN U
column chromatography eluted with petroleum ether/ethyl acetate (5:1) to give compound 8 (1.94 g, 90%) as a light yellow oil. [α]D25+115 (c 0.52, MeOH); 1H NMR (400 MHz, CDCl3) δH: 3.98-3.90 (m, 4H), 2.76-2.63 (m, 1H), 2.53-2.37 (m, 2H), 2.24-2.10 (m, 2H), 1.93-1.57 (m, 8H), 1.33 (s, 3H); 13C NMR (100 MHz, CDCl3) δc: 198.9, 160.4, 130.4, 113.0, 65.6, 65.3, 45.5, 33.9, 29.9, 26.75, 26.71, 21.7, 21.1, 11.7;
(100).
TE D
IR (KBr) νmax: 2941, 2856, 1707, 1686, 1458, 1175, 1262, 1032, 950 cm-1; MS [M+H]+ m/z (%): 237.2
EP
3, 5-Diethoxytoluene (13): See compound 21 for similar procedure. Compound 13 was obtained as pale yellow oil in 97% yield; 1H NMR (400 MHz, CDCl3) δH: 6.32 (d, J=1.6 Hz, 2H), 6.27 (s, 1H), 4.01 (q,
AC C
J=6.8 Hz, 4H), 2.28 (s, 3H), 1.39 (t, J=6.8 Hz, 6H); 13C NMR (100 MHz, CDCl3) δc: 160.2, 140.3, 107.8, 98.7, 63.5, 22.0, 15.1; IR (KBr) νmax: 2980, 2922, 1593, 1470, 1391, 1342, 1319, 1292, 1169, 1157, 1065, 818, 687 cm-1; MS [M+H]+ m/z (%): 181.1 (100).
2, 4-diethoxy-6-methylbenzaldehyde (14): A solution of phosphoryl chloride (12.1 mL, 130.6 mmol) in dried DMF (24 mL) was added to a stirred solution of 3, 5-Diethoxytoluene (19.6 g, 108.8 mmol) in 34
11
ACCEPTED MANUSCRIPT
mL of dried DMF at 100 - 110 oC over a period of 30 min under nitrogen atmosphere. Continue stirring at 100-110 oC for 1 hr, the reaction mixture was poured into ice-water. The pH of the aqueous solution was adjusted to pH 8 with saturated aqueous K2CO3 solution. The precipitate formed was collected and dried
RI PT
to afford 2, 4-diethoxy-6-methylbenzaldehycle (14) (20.6 g, 91%) as an off-white solid. Mp. 92-94 oC; 1H NMR (400 MHz, CDCl3) δH: 10.5 (s, 1H), 6.28 (s, 2H), 4.08 (q, J=7.2 Hz, 4H), 2.55 (s, 3H), 1.45 (t, J=6.8, 7.2 Hz, 6H); 13C NMR (100 MHz, CDCl3) δc: 190.9, 164.9, 164.0, 144.7, 117.5, 109.4, 97.1, 64.5, 63.9,
SC
22.5, 14.9, 14.8; IR (KBr) νmax: 2934, 2860, 2777, 1749, 1663, 1603, 1576, 1558, 1456, 1396, 1325, 1292,
M AN U
1163, 1115, 1057, 849, 837, 787, 700, 507 cm-1; MS [M+H]+ m/z (%): 209.2 (100).
2, 4-diethoxy-6-methylphenol (15): KHSO4 (2.53 g, 18.6 mmol) and 10% of H2O2 (11.6 mL, 114.0 mmol) were added to a solution of 14 (19.3 g, 92.7 mmol) in methanol (500 mL) sequentially at 4 oC. The mixture was stirred at 25 °C for 4 hrs, 5% aqueous solution of KHSO3 (15 mL) was added to quench the
TE D
reaction and the solvent was removed under reduced pressure. The residue was extracted with EtOAc (2 × 350 mL), the extract was washed with water (2 × 150 mL) and dried over Na2SO4. The solvent was removed under reduced pressure to give 15 (16.4g, 90%) as a light yellow solid. Mp. 116-118 oC; 1H
EP
NMR (400 MHz, CDCl3) δH: 6.34 (d, J=2.4 Hz, 1H), 6.27 (d, J=2.4 Hz, 1H), 5.32 (s, 1H), 4.08 (q, J=6.8 Hz, 2H), 3.98 (q, J=6.8 Hz, 2H), 2.23 (s, 3H), 1.44 (t, J=6.8, 7.2 Hz, 3H), 1.39 (t, J=6.8 Hz, 3H);
13
C
AC C
NMR (100 MHz, CDCl3) δc: 151.4, 145.3, 137.5, 123.1, 106.9, 97.7, 64.0, 63.5, 15.3, 14.5, 14.4; IR (KBr) νmax: 3433, 2924, 2853, 2856, 2362, 1655, 1657, 1458, 1465, 1240, 669 cm-1; MS [M+H]+ m/z (%): 197.3 (100).
1, 2, 5-triethoxy-3-methylbenzene (16): See compound 21 for similar procedure. Compound 16 was obtained as colorless oil in 96% yield; 1H NMR (400 MHz, CDCl3) δH: 6.33 (d, J=2.4 Hz, 1H), 6.27 (d,
12
ACCEPTED MANUSCRIPT
J=2.0 Hz, 1H), 4.03-3.92 (m, 6H), 2.24 (s, 3H), 1.44-1.33 (m, 9H);
13
C NMR (100 MHz, CDCl3) δc:
155.1, 152.8, 140.9, 132.3, 106.9, 99.6, 68.5, 64.3, 63.8, 16.7, 15.9, 15.1; IR (KBr) νmax: 3433, 2930, 2361,
RI PT
2330, 1707, 1466, 1331, 1117, 1072, 669 cm-1; MS [M+H]+ m/z (%): 225.1 (20).
2-bromo-3-(bromomethyl)-1, 4, 5-triethoxybenzene (7): To a solution of 16 (8.0 g, 35.7 mmol) in CCl4 (600 mL) was added AIBN (293 mg, 1.79 mmol) and NBS (20.4 g, 114.3 mmol). The mixture was
SC
refluxed for 4 hrs in the presence of light. The precipitate was filtered off and the filtrate was concentrated under reduce pressure to give the crude product. The residue was washed with 30 mL petroleum ether
M AN U
(containing 10% of ethyl acetate) to give compound 7 (11.0 g, 81%) as a pale yellow solid. Mp. 121-125 o
C; 1H NMR (400 MHz, CDCl3) δH: 6.51 (s, 1H), 4.75 (s, 2H), 4.15 (q, J=6.8, 7.2 Hz, 2H), 4.06 (q, J=6.8
Hz, 4H), 1.45-1.40 (m, 9H);
13
C NMR (100 MHz, CDCl3) δc: 151.6, 151.2, 141.4, 131.6, 104.9, 100.8,
68.9, 65.3, 64.2, 28.2, 15.2, 14.4; IR (KBr) νmax: 2976, 2934, 2889, 1558, 1657, 1458, 1419, 1387, 1339,
TE D
1244, 1215, 1115, 1034, 1003, 927, 881, 806 cm-1; MS [M+H]+ m/z (%): 381.0 (65).
(4a'S, 5'S, 8a'S)-5', 8a'-dimethylhexahydro-2'H-spiro [[1, 3]dioxolane-2, 1'-naphthalen]-6'(7'H)-one (17):
EP
A solution of compound 8 (200 mg, 0.85 mmol) and H2O (15.3 µL, 0.85 mmol) in THF (2 mL) was added drop wise to a solution of Li (24 mg, 3.4 mmol) in liquid ammonia (5 mL) at -78 °C in 30 min. The
AC C
reaction mixture was stirred at -35 °C for 1 hr. The reaction was quenched with ammonium chloride (500 mg). 10 mL H2O was added into the mixture and then extracted with ethyl ether (2 × 10 mL). The combined organic layer was dried over anhydrous Na2SO4 and concentrated under reduced pressure. The residue was purified by column chromatography eluted with petroleum ether/ethyl acetate (5:1) to give 17 (180 mg, 89%) as a colourless oil. [α]D25 −3.6 (c 0.96, CHCl3); 1H NMR (400 MHz, CDCl3) δH: 3.94-3.84 (m, 4H), 2.42-2.33 (m, 2H), 2.24-2.19 (m, 1H), 1.90-1.89 (m, 1H), 1.76-1.46 (m, 7H), 1.22 (s, 3H). 0.97(d,
13
ACCEPTED MANUSCRIPT
J=6.4 Hz, 3H);
13
C NMR (100 MHz, CDCl3) δc: 212.8, 112.5, 65.1, 64.9, 48.1, 44.9, 42.4, 37.5, 30.7,
29.9, 24.9, 22.7, 14.2, 11.7; IR (KBr) νmax: 2951, 2878, 1700, 1445, 1186, 1086, 1040, 916 cm-1; MS
RI PT
[M+H]+ m/z (%): 239.2 (100).
(4a'S, 5'S, 8a'S)-5'-(2-bromo-3, 5, 6-triethoxybenzyl)-5', 8a'-dimethylhexahydro-2'H-spiro [[1, 3] dioxolane-2, 1'-naphthalen]-6' (7'H)-one (6): See compound 23 for similar procedure. Compound 6 was
SC
obtained as white solid in 8% yield; Mp. 147-152 oC; [α]D25+29 (c 0.07, EtOH); 1H NMR (400 MHz, CDCl3) δH: 6.50 (s, 1H), 4.08-3.91 (m, 9H), 3.83-3.81 (m, 1H), 3.33 (d, J=13.6 Hz, 1H), 3.07 (d, J=13.6
Hz, 3H), 1.02 (s, 3H), 1.01 (s, 3H);
13
M AN U
Hz, 1H), 2.97-2.92 (m, 1H), 2.97-2.92 (m, 1H), 2.34-2.28 (m, 3H), 1.70-1.39 (m, 16H), 1.34 (t, J=6.8, 7.2 C NMR (100 MHz, CDCl3) δc: 215.4, 150.9, 150.6, 142.5, 132.1,
112.6, 107.6, 101.1, 67.8, 65.3, 64.9, 64.5, 64.1, 51.1, 47.3, 41.6, 40.1, 34.2, 29.3, 29.1, 22.6, 22.3, 17.8, 15.3, 14.5, 14.4; IR (KBr) νmax: 3369, 2928, 2864, 2361, 1709, 1578, 1383, 1339, 1232, 1184, 1117, 1074,
TE D
951, 810 cm-1; HRMS [M+Na]+ m/z 561.1796 (calc. 561.1822 for C27H39BrNaO6).
(4aS, 5S, 11S, 12aS)-7, 8, 10-triethoxy-5, 12a-dimethyl-3, 4, 4a, 5, 6, 11, 12, 12a-octahydro-2H-spiro [5,
EP
11-ethanodibenzo [a, e] [8] annulene-1, 2'-[1, 3] dioxolan]-13-one (18): See compound 32 for similar procedure. Compound 18 was obtained as pale yellow foam in 72% yield; [α]D25+37 (c 0.075, EtOH); 1H
AC C
NMR (400 MHz, CDCl3) δH: 6.40 (s, 1H), 4.07-3.77 (m, 10H), 3.66 (d, J=8.8, 13.2 Hz, 1H), 1.62-1.31 (m, 15H), 1.17 (s, 3H), 0.99 (s, 3H); 13C NMR (100 MHz, CDCl3) δc: 220.7, 151.4, 149.9, 139.2, 128.2, 123.7, 111.8, 97.6, 67.7, 64.7, 63.9, 63.4, 46.3, 46.1, 43.3, 42.2, 41.4, 38.6, 29.1, 22.7, 21.9, 17.5, 17.4, 15.3, 14.6, 14.5; IR (KBr) νmax: 2978, 2935, 2880, 2359, 2332, 1718, 1597, 1383, 1331, 1229, 1184, 1072, 1053, 914, 802 cm-1; HRMS [M+Na]+ m/z 481.2583 (calc. 481.2561 for C27H38NaO6).
14
ACCEPTED MANUSCRIPT
(4aR, 5S, 11S, 12aS)-7, 8, 10-triethoxy-5, 12a-dimethyl-2, 3, 4, 4a, 5, 6, 12, 12a-octahydro-5, 11-methanodibenzo [a, e] [8] annulene-1, 13 (11H)-dione (5): See compound 27 for similar procedure. Compound 5 was obtained as light yellow solid in 88% yield; Mp. 167-170 oC; [α]D25+12 (c 0.065, EtOH); H NMR (400 MHz, CDCl3) δH: 6.39 (s, 1H), 4.07-3.84 (m, 7H), 3.75 (d, J=9.2 Hz, 1H), 3.39 (d, J=17.2
RI PT
1
Hz, 1H), 2.63 (d, J=14.4 Hz, 1H), 2.55-2.49 (m, 3H), 2.22-2.02 (m, 4H), 1.84-1.78 (m, 3H), 1.46-1.25 (m, 12H), 1.09 (s, 3H); 13C NMR (100 MHz, CDCl3) δc: 219.0, 213.4, 151.5, 150.1, 138.9, 127.5, 123.0, 97.4,
SC
67.8, 64.1, 63.3, 49.2, 46.9, 46.5, 43.0, 41.6, 39.9, 37.2, 24.9, 22.8, 19.4, 17.5, 15.2, 14.5, 14.4; IR (KBr) νmax: 2976, 2938, 2872, 2361, 1718, 1701, 1597, 1470, 1387, 1331, 1232, 1128, 1072, 1036, 974, 800 cm-1;
M AN U
HRMS [M+Na]+ m/z 437.2318 (calc. 437.2298 for C25H34NaO5).
3, 5-Diethoxybenzyl alcohol (21): A mixture of 3, 5-dihydroxybenzyl alcohol (24 g, 171.3 mmol), diethyl sulfate (55.9 mL, 428.1 mmol) and potassium carbonate anhydrous (71.0 g, 513.9 mmol) in acetone (500
TE D
mL) was refluxed under nitrogen for 18 hrs. After cooling, the solution was filtered, the cake was washed with acetone (50 mL) and the filtrate was evaporated under reduced pressure. The residue was then purified by column chromatography eluted with petroleum ether/ethyl acetate (5:1) to give
EP
3,5-Diethoxybenzyl alcohol (21) (32.7 g, 97.3%) as a colorless liquid. 1H NMR (400 MHz, CDCl3) δH: 6.51 (d, J=2.4 Hz, 2H), 6.39 (t, J=2.0, 2.4 Hz, 1H), 4.62 (s, 2H), 4.03 (q, J=6.8 Hz, 4H), 1.42 (t, J=6.8 Hz,
AC C
6H); 13C NMR (100 MHz, CDCl3) δc: 159.8, 142.8, 104.6, 100.1, 64.9, 63.0, 14.3; IR (KBr) νmax: 3442, 2980, 2930, 1597, 1456, 1393, 1292, 1171, 1115, 1059, 1032, 972, 841, 708, 689 cm-1; MS [M+H]+ m/z (%): 197.1 (100).
1-(bromomethyl)-3, 5-diethoxybenzene (22): PBr3 (15.8 mL) was added dropwise to a solution of 3, 5-diethoxybenzyl alcohol (21) (32.7 g, 166.6 mmol) and pyridine (0.67 mL, 8.3 mmol) in DCM (500 mL)
15
ACCEPTED MANUSCRIPT
at 0 oC. The mixture was stirred at room temperature for 4 hrs. Then the reaction was quenched with ice water (600 mL), extracted with DCM (2 × 300 mL), washed with brine (2 × 200 mL), dried over anhydrous Na2SO4, and concentrated to provide 1-(bromomethyl)-3, 5-diethoxybenzene (22) as a grey
RI PT
solid. (42.3g, 98.4%) The crude product can be used for next step of reaction without further purification. Mp. 53-56 oC; 1H NMR (400 MHz, CDCl3) δ: 6.54 (d, J=2.4 Hz, 2H), 6.40 (t, J=2.0, 2.4 Hz, 1H), 4.43 (s, 2H), 4.03 (q, J=6.8 Hz, 4H), 1.42 (t, J=6.8 Hz, 6H); 13C NMR (100 MHz, CDCl3) δc: 159.7, 139.1, 107.0,
SC
101.0, 63.1, 33.3, 14.3; IR (KBr) νmax: 2972, 2930, 2883, 2862, 1684, 1597, 1558, 1456, 1394, 1317, 1169,
M AN U
1113, 1057, 847, 822, 690, 550, 498 cm-1; MS [M+H]+ m/z (%): 259.1 (80).
(4a'S, 5'S, 8a'S)-5'-(3, 5-diethoxybenzyl)-5', 8a'-dimethylhexahydro-2'H-spiro [[1, 3] dioxolane-2, 1'-naphthalen]-6' (7'H)-one (23): Compound 8 (1.2 g, 5.1 mmol) in dried THF (30 mL) was added dropwise to a stirred solution of lithium (321 mg, 45.9 mmol) in liquid ammonia (50 mL) at -78 °C under
TE D
argon. The resulting solution was refluxed for 1 hrs, and then a solution of 22 (9.16 g, 35.5 mmol) in dried THF (15 mL) was added. The mixture was allowed to stand for 2 hrs at 25 °C until liquid ammonia be evaporated. Then, the saturated aqueous ammonium chloride (20 mL) was added, and the mixture was
EP
extracted with diethyl ether (3 × 30 mL). The combined organic layer was washed with brine, dried over anhydrous Na2SO4. After removal the solvent under reduced pressure, the residue was purified by column
AC C
chromatography eluted with petroleum ether/ethyl acetate (10:1) to give 23 (1.74 g, 82%) as a white foam. [α]D25+47 (c 0.03, MeOH); 1H NMR (400 MHz, CDCl3) δH: 6.31 (t, J=2.0, 2.4 Hz, 1H), 6.24 (d, J=2.0 Hz, 2H), 4.00 (q, J=6.8 Hz, 4H), 3.91-3.80 (m, 4H), 3.10 (d, J=13.6 Hz, 1H), 2.49 (d, J=13.2 Hz, 1H), 2.41-2.38 (m, 1H), 2.31-2.25 (m, 1H), 1.76-1.55 (m, 4H), 1.52-1.37 (m, 11H), 1.13 (s, 3H), 1.10 (s, 3H); 13
C NMR (100 MHz, CDCl3) δc: 216.3, 159.1, 139.9, 112.2, 108.6, 99.7, 64.6, 64.3, 62.9, 51.8, 44.5, 42.7,
41.7, 35.0, 29.7, 27.4, 22.2, 21.9, 21.8, 16.0, 14.4; IR (KBr) νmax: 2978, 2935, 2363, 1699, 1595, 1173,
16
ACCEPTED MANUSCRIPT
1059, 949, 908, 866, 820, 719, 669 cm-1; HRMS [M+Na]+ m/z 439.2459 (calc. 439.2455 for C25H36NaO5 ).
2-bromo-1-(bromomethyl)-3, 5-diethoxybenzene (24): See compound 25 for similar procedure.
RI PT
Compound 24 was obtained as a white solid in 91% yield; Mp. 107-110 oC; 1H NMR (400 MHz, CDCl3) δH: 6.62 (d, J=2.8 Hz, 1H), 6.43 (d, J=2.4 Hz, 1H), 4.60 (s, 2H), 4.08 (m, 4H), 1.50 (t, J=6.8 Hz, 3H), 1.54 (t, J=6.8, 7.2 Hz, 3H);
13
C NMR (100 MHz, CDCl3) δc: 158.5, 156.0, 137.9, 107.2, 104.8, 100.8, 64.5,
SC
63.4, 33.7, 14.3, 14.2; IR (KBr) νmax: 2982, 2934, 2885, 1603, 1582, 1456, 1391, 1331, 1184, 1117, 1074,
M AN U
1026, 889, 851, 806, 717, 660, 627 cm-1; MS [M+H]+ m/z (%) 337.0 (15).
(4a'S, 5'S, 8a'S)-5'-(2-bromo-3, 5-diethoxybenzyl)-5', 8a'-dimethylhexahydro-2'H-spiro [[1, 3] dioxolane-2, 1'-naphthalen]-6'(7'H)-one (25): To a solution of 23 (1.60 g, 3.84 mmol) in DCM (75 mL), NBS (0.72 g, 4.03 mmol) was added at 0 °C and the reaction was stirred at 0 oC for 1 hrs. The reaction mixture was
TE D
quenched with saturated aqueous NaHCO3 (15 mL). Then the mixture was diluted with H2O (30 mL), extracted with EtOAc (3 × 60 mL). The combined organic layer was then washed with brine (20 mL), dried over anhydrous MgSO4, and then concentrated under reduced pressure. The residue was purified by
EP
column chromatography eluted with petroleum ether/ethyl acetate (10:1) to give compound 25 (1.83 g, 92%) as a white foam. [α]D25 +10 (c 0.06, MeOH); 1H NMR (400 MHz, CDCl3) δH: 6.31 (d, J=2.8 Hz, 1H),
AC C
6.21 (d, J=2.4 Hz, 1H), 4.03-3.79 (m, 8H), 3.15 (d, J=14.4 Hz, 1H), 3.00 (d, J=14.0 Hz, 1H), 2.47-2.43 (m, 2H), 2.22-2.19 (m, 1H), 1.84-1.81 (m, 1H), 1.65-1.33 (m, 13H), 1.06 (s, 6H); 13C NMR (100 MHz, CDCl3) δc: 216.9, 157.6, 155.3, 138.9, 112.1, 107.7, 107.1, 99.6, 64.5, 64.4, 64.2, 63.0, 51.9, 44.3, 43.4, 41.7, 35.0, 29.4, 27.8, 22.4, 22.1, 20.6, 16.3, 14.2, 14.1; IR (KBr) νmax: 2982, 2937, 2883, 1697, 1657, 1589, 1340, 1178, 1138, 1045, 1020, 951, 806 cm-1; HRMS [M+Na]+ m/z 517.1556 (calc. 517.1560 for C25H35BrNaO5).
17
ACCEPTED MANUSCRIPT
(4aS, 5S, 11S, 12aS)-8,10-diethoxy-5, 12a-dimethyl-3, 4, 4a, 5, 6, 11, 12, 12a-octahydro-2H-spiro [5, 11-methanodibenzo [a, e] [8] annulene-1, 2'-[1, 3] dioxolan]-13-one (26): An oven-dried 100 mL
RI PT
round-bottomed flask was charged with Pd2(dba)3 (439 mg, 0.49 mmol), xant-Phos (232 mg, 0.49 mmol) and anhydrous t-BuONa (701 mg, 7.29 mmol). A solution of 25 (1200 mg, 2.43 mmol) in anhydrous dioxane (30 mL) was added under Ar, and the suspension was heated to reflux for 4 hrs. After cooling to
SC
25 °C, the reaction mixture was diluted with EtOAc (30 mL), filtered over celite, and concentrated under reduced pressure. The residue was purified by column chromatography eluted with petroleum ether/ethyl
M AN U
acetate (12:1) gave 26 (886 mg, 88%) as a pale yellow foam. 1H NMR (400 MHz, CDCl3) δH: 6.32 (s, 1H), 6.13 (s, 1H), 4.04-3.96 (m, 4H), 3.88-3.77 (m, 4H), 3.66 (d, J=9.2 Hz, 1H), 3.03 (d, J=16.4 Hz, 1H), 2.75 (d, J=16.4 Hz, 1H), 2.64-2.60 (m, 1H), 2.45 (d, J=13.6 Hz, 1H), 1.95 (t, J=9.2, 4.0 Hz, 1H), 1.14 (s, 3H), 1.00 (s, 3H); 13C NMR (100 MHz, CDCl3) δc: 220.21, 158.1, 156.5, 134.5, 123.3, 111.9, 103.9, 97.5, 64.7,
TE D
63.9, 62.9, 62.8, 48.5, 46.7, 46.2, 42.0, 41.3, 38.3, 29.1, 22.8, 22.0, 17.3, 14.42, 14.36; IR (KBr) νmax: 3367, 3337, 2980, 2934, 2883, 1717, 1178, 1134, 1072, 1022 cm-1; [α]D25+43 (c 0.075, MeOH); HRMS
EP
(ESI+): [M+Na]+ m/z 437.2303 (calc. 437.2298 for C25H34NaO5).
(4aR, 5S, 11S, 12aS)-8, 10-diethoxy-5, 12a-dimethyl-2, 3, 4, 4a, 5, 6, 12, 12a-octahydro-5,
AC C
11-ethanodibenzo [a, e] [8] annulene-1, 13(11H)-dione (27): 3.0 M hydrochloric acid (9.7 mL, 39.8 mmol) was added to a stirred solution of 26 (1.10 g, 2.66 mmol) in THF (20 mL) at 25 °C. After 2 h stirring, the reaction was quenched with saturated aqueous sodium hydrogen carbonate (6 mL), and the mixture was extracted with ethyl acetate (3 × 30 mL). The combined extracts were washed with brine (30 mL), dried over anhydrous Na2SO4, concentrated under reduced pressure afforded an oily residue, which was purified by column chromatography using petroleum ether/ethyl acetate (12:1) as elute gave 27 (905 mg, 92%) as
18
ACCEPTED MANUSCRIPT
a pale yellow solid. Mp. 147-151 oC; [α]D25+28 (c 0.05, MeOH); 1H NMR (400 MHz, CDCl3) δH: 6.29 (s, 1H), 6.09 (s, 1H), 4.03-3.93 (m, 4H), 3.73 (d, J=9.6 Hz, 1H), 3.03 (d, J=16.8 Hz, 1H), 2.76 (d, J=16.4 Hz, 1H), 2.57-2.44 (m, 3H), 2.19-2.00 (m, 1H), 1.81-1.73 (m, 2H), 1.47-1.39 (m, 7H), 1.22 (s, 3H), 1.06 (s,
RI PT
3H); 13C NMR (100 MHz, CDCl3) δc: 218.5, 213.2, 158.4, 156.6, 133.8, 122.9, 103.8, 97.4, 62.97, 62.92, 48.9, 48.1, 46.9, 46.8, 41.4, 39.8, 37.1, 24.9, 22.8, 19.3, 17.4, 14.4, 14.3; IR (KBr) νmax: 2934, 2378, 2303, 2181, 1705, 1508, 1178, 1121, 1070, 839 cm-1; HRMS [M+Na]+ m/z 393.2039 (calc. 393.2036 for
SC
C23H30NaO4).
M AN U
(4aR, 5S, 11R, 12aS)-8, 10-diethoxy-5, 12a-dimethyl-1, 13-dimethylene-1, 2, 3, 4, 4a, 5, 6, 11, 12, 12a-decahydro-5, 11-methanodibenzo [a, e] [8] annulene (28): A mixture of t-BuOK (3.75g, 33.4 mmol) and methyltriphenylphosphonium bromide (12.54g, 35.1 mmol) in dry toluene (80 mL) was refluxed at 90 o
C for 1 hr under argon. The resulted solution was cooled to 25 °C. A solution of 27 (650 mg, 1.76 mmol)
TE D
in toluene (50 mL) was added to above prepared mixture. The reactant was stirred at 90 oC for 40 hrs under argon and quenched with water (60 mL). After extracted with EtOAc (2 × 50 mL), the combined organic layer was washed with brine (30 mL), dried over anhydrous Na2SO4. After concentered under
EP
reduced pressure, the residue was purified by column chromatography eluted with petroleum ether/ethyl acetate (100:1) gave 27 (580 mg, 90%) as a pale yellow solid. Mp. 85-89 oC; [α]D25+46 (c 0.07, MeOH); H NMR (400 MHz, CDCl3) δH: 6.31 (d, J=2.0 Hz, 1 H), 6.11 (d, J=2.0 Hz, 1H), 4.93 (d, J=0.8 Hz, 1H),
AC C
1
4.82 (d, J=1.2 Hz, 1H), 4.51 (d, J=1.2 Hz, 1H); 4.08-3.91 (m, 5H), 2.81 (d, J=16.0 Hz, 1H), 2.46 (d, J=15.6 Hz, 1H), 1.81-1.73 (m, 2H), 1.47-1.39 (m, 7H), 1.22 (s, 3H), 1.06 (s, 3H);
13
C NMR (100 MHz,
CDCl3) δc: 158.6, 157.4, 155.9, 155.3, 136.4, 126.3, 104.9, 104.5, 102.9, 97.0, 62.8, 48.7, 46.6, 43.5, 39.3, 38.4, 37.4, 32.7, 26.9, 24.5, 21.9, 20.5, 14.53, 14.48; IR (KBr) νmax: 2972, 2926, 2907, 2868, 1603, 1587, 1437, 1340, 1285, 1180, 1146, 1122, 1092, 1068, 885, 839 cm-1; HRMS [M+Na]+ m/z 389.2455 (calc.
19
ACCEPTED MANUSCRIPT
389.2451 for C25H34NaO2).
(5R, 6aS, 10aR, 11S)-2-ethoxy-6a, 11-dimethyl-7, 13-dimethylene-5, 6, 6a, 7, 8, 9, 10, 10a, 11,
RI PT
12-decahydro-5, 11-methanodibenzo [a, e] [8] annulene-1, 4-dione (2): A solution of CrO3 (467 mg, 4.67 mmol) in H2O (2 mL) and AcOH (8 mL) was added drop wisely to the solution of compound 27 (450 mg, 1.23 mmol) in AcOH (12 mL) at 0 °C. The reaction mixture was stirred at room temperature and
SC
monitored by TLC (petroleum ether/EtOAc=10:1). After 30 min, ice water (20 mL) was added, and the aqueous layer was extracted with EtOAc (2 × 30 mL). The combined organic layers were washed with
M AN U
saturated NH4Cl solution (30 mL), dried over anhydrous Na2SO4. After filtration, the solution was concentration under reduced pressure. The residue was purified by column chromatography using petroleum ether/ethyl acetate (10:1) as elute to give 2 (295 mg, 68%) as a pale yellow solid. Mp. 88-93 oC; [α]D25+17 (c 0.06, MeOH); 1H NMR (400 MHz, CDCl3) δH: 5.86 (s, 1H), 4.93 (s, 1H), 4.86 (s, 1H), 4.54
TE D
(s, 1H), 4.50 (s, 1H), 4.00 (q, J=6.8 Hz, 2H), 3.77 (d, J=10.8 Hz, 1H), 2.75 (d, J=18.4 Hz, 1H), 2.22-1.95 (m, 6H), 1.83-1.79 (m, 1H), 1.70-1.67 (m, 2H), 1.56-1.43 (m, 5H), 1.24 (s, 3H), 1.09 (s, 3H);
13
C NMR
(100 MHz, CDCl3) δc: 186.2, 182.3, 157.6, 157.3, 151.5, 148.5, 138.1, 107.1, 105.6, 105.2, 64.6, 48.7,
EP
42.4, 41.6, 38.8, 37.8, 36.7, 32.6, 26.9, 24.3, 21.3, 20.2, 13.4; IR (KBr) νmax: 2930, 2860, 1717, 1647,
AC C
1219, 1111, 1034, 980, 891 cm-1; HRMS [M+Na]+ m/z 375.1937 (calc. 375.1931 for C23H28NaO3).
(5R, 6aS, 10aR, 11S)-2-ethoxy-6a, 7, 11-trimethyl-13-methylene-6, 6a, 10, 10a, 11, 12-hexahydro-5, 11-methanodibenzo [a, e] [8] annulene-1, 4(5H, 9H)-dione (1): To a solution of 2 (100 mg, 0.28 mmol) in AcOH (20 mL) was added PTSA (10 mg, 0.06 mmol), the mixture was stirred at 25 oC for 12 hrs. Then the solution was diluted with ice water (50 mL) and extracted into tert-Butyl methyl ether (3 × 20 mL). The combined extract was washed with brine (2 × 20 mL), dried over anhydrous Na2SO4 and concentrated
20
ACCEPTED MANUSCRIPT
under reduced pressure. The residue was purified by column chromatography eluted with petroleum ether/ethyl acetate (10:1) to give compound 1 (92 mg, 92%) as a pale solid. Mp = 99-102 oC; [α]D25+119 (c 0.13, MeOH); 1H NMR (400 MHz, CDCl3) δH: 5.85 (s, 1H), 5.09 (s, 1H), 4.91 (s, 1H), 4.85 (s, 1H),
RI PT
4.00 (q, J=6.8, 7.2 Hz, 2H), 3.72 (d, J=10.4 Hz, 1H), 2.79 (d, J=18.4 Hz, 1H), 2.19-2.22 (dd, J=10.4, 14.0 Hz, 1H), 2.02-1.98 (m, 1H); 1.90-1.85 (m, 1H), 1.69-1.63 (m, 2H), 1.54-1.45 (m, 8H), 1.25 (s, 3H), 1.05 (s, 3H);
13
C NMR (100 MHz, CDCl3) δc: 186.2, 182.3, 157.3, 152.0, 148.6, 142.1, 138.8, 118.9, 107.1,
SC
105.1, 64.6, 46.8, 42.4, 41.4, 37.4, 37.2, 36.6, 25.9, 19.96, 19.88, 19.3, 17.5, 13.4; IR (KBr) νmax: 2964, 2937, 1697, 1670, 1677, 1630, 1601, 1339, 1279, 1225, 1209, 1161, 1101, 1034, 889, 850 cm-1; HRMS
M AN U
[M+Na]+ m/z 375.1936 (calc. 375.1931 for C23H28NaO3 ).
(4a'S, 5'S, 8a'S)-5'-(3, 5-dimethoxybenzyl)-5', 8a'-dimethylhexahydro-2'H-spiro [[1, 3] dioxolane-2, 1'-naphthalen]-6'(7'H)-one (30): See compound 23 for similar procedure. Compound 30 was obtained as
TE D
white foam in 83% yield; [α]D25+27 (c 0.13, MeOH); 1H NMR (400 MHz, CDCl3) δH: 6.32 (t, J=2.0, 2.4 Hz, 1H), 6.26 (d, J=2.4 Hz, 1H), 3.91-3.80 (m, 4H), 3.71 (s, 6H), 3.13 (d, J=13.6 Hz, 1H); 3.72 (d, J=13.6 Hz, 1H), 2.48-2.37 (m, 1H), 2.31-2.25 (m, 2H), 1.75-1.65 (m, 3H), 1.54-1.43 (m, 5H), 1.14 (s, 3H), 1.11 13
C NMR (100 MHz, CDCl3) δc: 216.2, 159.8, 140.2, 112.1, 107.9, 98.5, 64.6, 64.3, 54.8, 51.8,
EP
(s, 3H);
44.4, 42.6, 41.7, 35.0, 29.7, 27.3, 22.2, 21.9, 21.8, 15.9; IR (KBr) νmax: 2943, 2883, 2837, 1701, 1595,
AC C
1460, 1429, 1344, 1294, 1205, 1184, 1151, 1099, 1059, 1045, 910, 829, 708 cm-1; HRMS [M+Na]+ m/z 411.2161 (calc. 411.2142 for C23H32NaO5).
(4a'S, 5'S, 8a'S)-5'-(2-bromo-3, 5-dimethoxybenzyl)-5', 8a'-dimethyl-hexahydro-2'H-spiro [(1, 3) -dioxolane-2, 1'-naphthalen]-6'(7'H)-one (31): See compound 25 for similar procedure. Compound 31 was obtained as white foam in 91% yield; [α]D25+25 (c 0.08, MeOH); 1H NMR (400 MHz, CDCl3) δH: 6.34 (d,
21
ACCEPTED MANUSCRIPT
J=2.8 Hz, 1H), 6.25 (d, J=2.8 Hz, 1H), 3.89-3.79 (m, 7H), 3.73 (s, 3H), 3.18 (d, J=13.2 Hz, 1H), 3.03 (d, J=14.0 Hz, 1H), 2.49-2.43 (m, 2H), 2.23-2.19 (m, 1H), 1.84-1.82 (m, 1H), 1.77-1.41 (m, 7H), 1.09 (s, 3H), 1.08 (s, 3H); 13C NMR (100 MHz, CDCl3) δc: 217.2, 158.4, 155.9, 139.2, 112.2, 107.0, 103.7, 97.9, 64.6,
RI PT
64.3, 55.8, 54.9, 52.1, 44.3, 43.4, 41.8, 35.1, 29.5, 27.8, 22.4, 22.2, 20.8, 16.3; IR (KBr) νmax: 2937, 2881, 2856, 1701, 1591, 1458, 1437, 1381, 1340, 1288, 1202, 1163, 1082, 1022, 949, 910 cm-1; HRMS
SC
[M+Na]+ m/z 489.1259 (calc. 489.1247 for C23H31BrNaO5).
(4aS, 5S, 11S, 12aS)-8, 10-dimethoxy-5, 12a-dimethyl-3, 4, 4a, 5, 6, 11, 12, 12a-octahydro-2H-spiro [5,
M AN U
11-methanodibenzo [a, e] [8] annulene-1, 2'-[1, 3] dioxolan]-13-one (32): In a sealed tube was charged with Pd(OAc)2 (225 mg, 1.0 mmol), PPh3 (262 mg, 1.0 mmol) and Cs2CO3 (3257 mg, 9.99 mmol), a solution of 31 (1550 mg, 3.33 mmol) in anhydrous THF (60 mL) was added, the resulting suspension was heated to 100 oC for 24 hrs. After cooling to 25 °C, the reaction mixture was diluted with EtOAc (30 mL),
TE D
filtered through celite and then concentrated under vacuum. The residue was purified by column chromatography eluted with petroleum ether/ethyl acetate (10:1) gave 32 (1093 mg, 85%) as a white foam. [α]D25+84 (c 0.05, MeOH); 1H NMR (400 MHz, CDCl3) δH: 6.34 (d, J=2.0 Hz, 1H), 6.15 (d, J=2.0 Hz,
EP
1H), 3.89-3.87 (m, 3H), 3.80-3.78 (m, 7H), 3.65 (d, J=9.2 Hz, 1H), 3.05 (d, J=16.4 Hz, 1H), 2.71 (d, J=16.4 Hz, 1H), 2.63 (dd, J=4.8, 12.0 Hz, 1H), 2.42 (d, J=13.6 Hz, 1H), 1.95 (dd, J=9.2, 13.6 Hz, 1H),
AC C
1.67-1.33 (m, 7H), 1.15 (s, 3H), 1.00 (s, 3H); 13C NMR (100 MHz, CDCl3) δc: 219.9, 158.8, 157.4, 134.6, 123.4, 111.8, 103.4, 96.5, 64.7, 63.9, 54.9, 54.7, 48.5, 46.7, 46.2, 41.9, 41.3, 38.4, 29.0, 22.8, 21.9, 17.3; IR (KBr) νmax: 3431, 2976, 2937, 1717, 1609, 1589, 1458, 1339, 1209, 1132, 1074, 1053, 1018, 939, 825 cm-1; HRMS [M+Na]+ m/z 409.1994 (calc. 409.1985 for C23H30NaO5).
(4aR, 5S, 11S, 12aS)-8, 10-dimethoxy-5, 12a-dimethyl-2, 3, 4, 4a, 5, 6, 12, 12a-octahydro-5,
22
ACCEPTED MANUSCRIPT
11-methanodibenzo [a, e] [8] annulene-1, 13(11H)-dione (33): See compound 27 for similar procedure. Compound 33 was obtained as white solid in 93% yield; Mp. 138−143 oC; [α]D25+37 (c 0.07, MeOH); 1H NMR (400 MHz, CDCl3) δH: 6.33 (d, J=2.0 Hz, 1H), 6.13 (d, J=1.6 Hz, 1H), 3.81(s, 3H), 3.77 (s, 3H),
3H), 1.85-1.76 (m, 2H), 1.53-1.43 (m, 1H), 1.25 (s, 3H), 1.09 (s, 3H);
RI PT
3.72 (d, J=9.6 Hz, 1H), 3.06 (d, J=16.4 Hz, 1H), 2.81 (d, J=16.4 Hz, 1H), 2.59-2.47 (m, 3H), 2.22-2.02 (m, 13
C NMR (100 MHz, CDCl3) δc:
218.2, 213.3, 159.1, 157.3, 133.9, 123.0, 103.3, 96.3, 54.9, 54.8, 48.9, 48.1, 46.98, 46.88, 41.3, 39.8, 37.1,
SC
24.9, 22.8, 19.4, 17.4; IR (KBr) νmax: 3475, 2939, 2899, 1705, 1605, 1593, 1489, 1458, 1356, 1207, 1145,
M AN U
1120, 1053, 976 928, 831 cm-1; HRMS [M+Na]+ m/z 365.1732 (calc. 365.1723 for C21H26NaO4).
(4aR, 5S, 11R, 12aS)-8, 10-dimethoxy-5, 12a-dimethyl-1, 13-dimethylene-1, 2, 3, 4, 4a, 5, 6, 11, 12, 12a-decahydro-5, 11-ethanodibenzo [a, e] [8] annulene (34): See compound 28 for similar procedure. Compound 34 was obtained as white solid in 92% yield; Mp. 81−86 oC; [α]D25+66 (c 0.085, MeOH); 1H
TE D
NMR (400 MHz, CDCl3) δH: 6.32 (d, J=2.0 Hz, 1H), 6.13 (d, J=2.0 Hz, 1H), 4.92 (d, J=0.8 Hz, 1H), 4.81 (d, J=1.2 Hz, 1H), 4.51 (d, J=1.6 Hz, 1H), 3.90 (dd, J=5.2, 5.6 Hz, 1H), 3.84 (s, 3H), 3.77 (s, 3H), 2.82 (d, J=16.0 Hz, 1H), 2.46 (d, J=16.0 Hz, 1H), 2.27-2.20 (m, 1H), 2.11-2.05 (m, 3H), 1.80-1.54 (m, 3H), 1.23 13
C NMR (100 MHz, CDCl3) δc: 158.5, 158.1, 156.6, 155.1, 136.5, 126.1, 105.1,
EP
(s, 3H), 1.13 (s, 3H);
103.9, 102.9, 95.9, 54.9, 54.8, 48.7, 46.7, 43.5, 39.3, 38.4, 37.3, 32.7, 26.9, 24.5, 21.9, 20.5; IR (KBr) νmax:
AC C
2989, 2930, 2854, 1630, 1605, 1593, 1487, 1458, 1354, 1213, 1196, 1088, 1122, 879, 827, 770, 629 cm-1; HRMS [M+Na]+ m/z 361.2143 (calc. 361.2138 for C23H30NaO2).
(5R, 6aS, 10aR, 11S)-2-methoxy-6a, 11-dimethyl-7, 13-dimethylene-5, 6, 6a, 7, 8, 9, 10, 10a, 11, 12-decahydro-5, 11-methanodibenzo [a, e] [8] annulene-1, 4-dione (3): See compound 2 for similar procedure. Compound 3 was obtained as light yellow solid in 67% yield; Mp. 86-91 oC; [α]D25+19 (c
23
ACCEPTED MANUSCRIPT
0.075, MeOH); 1H NMR (400 MHz, CDCl3) δH: 5.89 (s, 1H), 4.94 (s, 1H), 4.87 (s, 1H), 4.56 (s, 1H), 4.51 (s, 1H), 3.81 (s, 3H), 3.77 (s, 3H), 2.82 (d, J=16.0 Hz, 1H), 2.46 (d, J=16.0 Hz, 1H), 2.27-2.20 (m, 1H), 2.11-2.05 (m, 3H), 1.80-1.54 (m, 3H), 1.23 (s, 3H), 1.13 (s, 3H); 13C NMR (100 MHz, CDCl3) δc: 185.9,
RI PT
182.2, 158.1, 157.6, 151.4, 148.7, 138.2, 106.9, 105.6, 105.3, 55.7, 48.8, 42.4, 41.6, 38.8, 37.8, 36.8, 32.6, 26.9, 24.4, 21.3, 20.2; IR (KBr) νmax: 2964, 2926, 2877, 1697, 1670, 1647, 1602, 1558, 1458, 1231, 1221,
SC
1030, 885, 851, 775 cm-1; HRMS [M+Na]+ m/z 361.1781 (calc. 361.1774 for C22H26NaO3).
(5R, 6aS, 10aR, 11S)-2-methoxy-6a, 7, 11-trimethyl-13-methylene-6, 6a, 10, 10a, 11, 12-hexahydro-5,
M AN U
11-methanodibenzo [a, e] [8] annulene-1, 4(5H, 9H)-dione (4): See compound 1 for similar procedure. Compound 4 was obtained as light yellow solid in 90% yield; Mp. 95−98 oC; [α]D25+129 (c 0.085, MeOH); 1
H NMR (400 MHz, CDCl3) δH: 5.88 (s, 1H), 5.09 (d, J=3.2 Hz, 1H), 4.92 (s, 1H), 4.86 (s, 1H), 3.81 (s,
3H), 3.73 (d, J=10.4 Hz, 1H), 2.80 (d, J=18.8 Hz, 1H), 2.20 (dd, J=10.4, 13.6 Hz, 1H), 2.04 (d, J=18.4 Hz,
TE D
2H), 1.90-1.86 (m, 1H), 1.70-1.66 (m, 2H), 1.55-1.49 (m, 5H), 1.26 (s, 3H), 1.06 (s, 3H); 13C NMR (100 MHz, CDCl3) δC: 185.9, 182.2, 158.1, 157.6, 151.4, 148.7, 138.2, 106.9, 105.6, 105.3, 55.7, 48.8, 42.4, 41.6, 38.8, 37.8, 36.8, 32.6, 26.9, 24.4, 21.3, 20.2; IR(KBr) νmax: 2959, 2935, 1697, 1670, 1647, 1602,
EP
1558, 1375, 1340, 1229, 1211, 1099, 1026, 1005, 887, 845 cm-1; HRMS [M+Na]+ m/z 361.1786 (calc.
AC C
361.1774 for C22H26NaO3).
IC50 Value Determination for Human Kidney Carcinoma Cell lines 786-O and Human Prostate Cancer Cell lines PC-3. Human kidney carcinoma cells 786-O and human prostate cancer cells PC-3 were inoculated into 96 well microtiter plates at 10,000 and 7,500 cells/well in RPMI-1640 and DMEM/F12 medium containing 5% fetal bovine serum. After cell inoculation, the microtiter plates are incubated at 37° C, 5% CO2, 95% air and 100% relative humidity for 24 hrs prior to addition of experimental drugs.
24
ACCEPTED MANUSCRIPT
After 24 hrs, two plates of each cell line are fixed in situ with TCA, to represent a measurement of the cell population for each cell line at the time of compounds addition. At the time of compounds addition, different compounds dilutions are added to the appropriate microtiter wells already resulting in the
RI PT
required final drug concentrations. Following compounds addition, the plates are incubated for an additional 48 hrs at 37 °C, 5% CO2, 95% air, and 100% relative humidity. Cells are fixed in situ by cold 50% (w/v) TCA and incubated for 1 hr at 4 °C. The plates are washed five times with water and air dried.
SC
Sulforhodamine B (SRB) solution (100 µL) at 0.4% (w/v) in 1% acetic acid is added to each well, and plates are incubated for 10 minutes at room temperature. After staining, unbound dye is removed by
M AN U
washing five times with 1% acetic acid and the plates are air dried. Bound stain is subsequently solubilized with 10 mM trizma base, and the absorbance is read on an automated plate reader at a wavelength of 515 nm.
TE D
Acknowledgment
This research was supported by Science & Technology Commission of Shanghai municipality (grant number: 14401900600) and Jiangsu municipal government (333 high level talent funding project, grant
EP
number: BRA2013081). The authors would like to thank Miss. Runzhong Fu from University of South California, U.S.A for a very helpful linguistic modification. The authors also appreciate the help provided
AC C
by Prof. Peilan He from Shanghai Institute of Material Medica, Chinese Academy of Sciences and Dr. Yibo Wang from Basilea Pharmaceutica China Ltd.
References
(1) Faulkner, D. J. Nat. Prod. Rep. 1996, 13, 75-125. (2) An, J. G.; Wiemer, D. F. J. Org. Chem. 1996, 61, 8775-8779.
25
ACCEPTED MANUSCRIPT
(3) Ciavatta, M. L.; Lopez Gresa, M. P.; Gavagnin, M.; Romero, V.; Melck, D.; Manzo, E.; Guo, Y. W.; Van Soest, R.; Cimino, G. Tetrahedron 2007, 63, 1380-1384. (4) Mcnamara, C. E.; Larsen, L.; Perry, N. B.; Harper, J. L.; Berridge, M. V.; Chia, E. W.; Kelly, M.;
RI PT
Webb, V. L. J. Nat. Prod. 2005, 68, 1431-1433.
(5) (a) Jiao, W. H.; Huang, X. J.; Yang, J. S.; Yang, F.; Piao, S. J.; Gao, H.; Li, J.; Ye, W. C.; Yao, X. S.; Chen, W. S.; Lin, H. W. Org. Lett. 2012, 14, 202-205. (b) Jiao, W. H.; Xu, T. T.; Yu, H. B.; Chen, G.
SC
D.; Huang, X. J.; Yang, F.; Li, Y. S.; Han, B. N.; Liu, X. Y.; Lin, H. W. J. Nat. Prod. 2014, 77, 346-350.
M AN U
(6) (a) Schmalzbauer, B.; Herrmann, J.; Müller, R.; Menche, D. Org. Lett. 2013, 15, 964-967. (b) Fukui, Y.; Narita, K.; Katoh, T. Chem. Eur. J. 2014, 20, 2436-2439.
(7) (a) Smith III, A. B.; Mewshar, R. J. Org. Chem. 1984, 49, 3685-3689. (b) Corey, E. J.; Roberts, B. E. J. Am. Chem. Soc. 1997, 119, 12425-12431. (c) Petra, S.; Herbert, W. Angew. Chem. 1999, 111,
TE D
3935-3938. (d) Ling, T.; Rivas, F.; Theodorakis, E. A. Tetrahedron Lett. 2002, 43, 9019-9022. (e) Junji, S.; Takuya, K.; Kazuhiro, W.; Tadashi, K.; Ohgi, T. Eur. J. Org. Chem. 2011, 16, 2948-2957. (8) (a) Hagiwara, H.; Uda, H. J. Org. Chem. 1988, 53, 2308-2311. (b) Ling, T.; Xu, J.; Smith, R.;
EP
Theodorakis, E. A.; Ali, A.; Cantrell, C. L. Tetrahedron 2011, 67, 3023-3029. (c) Takahashi, S.; Oritani, T.; Yamashita, K. Tetrahedron 1988, 44, 7081-7088. (d) Ling, T.; Poupon, E.; Rueden, E. J.;
AC C
Kim, S. H.; Theodorakis, E. A. J. Am. Chem. Soc. 2002, 124, 12261-12267. (e) Cheung, A. K.; Murelli, R.; Snapper, M. L. J. Org. Chem. 2004, 69, 5712-5719. (f) Patent: Koch, M. A.; Odermatt, A.; Waldmann, H.; Scheck, M. WO 200669787, 2006 [Chem. Abstr. 2006, 145, 124765]. (g) Pereira, A. R.; Strangman, W. K.; Marion, F.; Feldberg, L.; Roll, D.; Mallon, R.; Hollander, I.; Andersen, R. J. J. Med. Chem. 2010, 53, 8523-8533. (h) Scheck, M.; Koch, M. A.; Waldmann, H. Tetrahedron 2008, 64, 4792-4802.
26
ACCEPTED MANUSCRIPT
(9) (a) Stahl, P.; Waldmann, H. Angew. Chem. Int. Ed. 1999, 38, 3710-3713. (b) Poigny, S.; Guyot, M.; Samadi, M. J. Org. Chem. 1998, 63, 5890-5894. (c) Stahl, P.; Kissau, L.; Mazitschek, R.; Huwe, A.; Furet, P.; Giannis, A.; Waldmann, H. J. Am. Chem. Soc. 2001, 123, 11586-11593. (d) Bruner, S. D.;
RI PT
Radeke, H. S.; Tallarico, J. A.; Snapper, M. L. J. Org. Chem. 1995, 60, 1114-1115. (e) Fretz, S. J.; Hadad, C. M.; Hart, D. J.; Vyas, S.; Yang, D. J. Org. Chem. 2013, 78, 83-92. (f) Snitman, D. L.; Tsai, M. Y.; Watt, D. S. J. Org. Chem. 1979, 44, 2838-2842.
SC
(10) Locke, E. P.; Hecht, S. M. Chem. Commun. 1996, 2717-2718.
(11) (a) Lanfranchi, D. A.; Hanquet, G. J. Org. Chem. 2006, 71, 4854-4861. (b) Ali, M. H.; Niedbalski, M.;
M AN U
Bohnert, G.; Bryant, D. Syn. Commun. 2006, 36, 1751-1759. (c) Yamazaki, S. Tetrahedron Lett. 2001, 42, 3355-3358. (d) Bissel, P.; Nazih, A.; Sablong, R.; Lepoittevin, J. P. Org. Lett. 1999, 1, 1283-1285. (12) (a) Bradshaw, B.; Etxebarria-Jardi, G.; Bonjoch, J. Org. Biomol. Chem. 2008, 6, 772-. (b) Chaudhury,
AC C
EP
TE D
S.; Li, S.; Donaldson, W. A. Chem. Commun. 2006, 19, 2069-2070.
27
ACCEPTED MANUSCRIPT
Total Synthesis of Dysidavarone A
7 Steps, 34% overall yield
O
+ O
O
EtO
OEt
H
SC
Br
RI PT
Chunhui Yu, Xiaoguang Zhang, Jinghua Zhang and Zhengwu Shen*
O
OEt
O
AC C
EP
TE D
M AN U
Dysidavarone A