Total synthesis and biological evaluation of clavaminol-G and its analogs

European Journal of Medicinal Chemistry 67 (2013) 384e389

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European Journal of Medicinal Chemistry journal homepage: http://www.elsevier.com/locate/ejmech

Original article

Total synthesis and biological evaluation of clavaminol-G and its analogs T. Vijai Kumar Reddy a, B.L.A. Prabhavathi Devi a, *, R.B.N. Prasad a, P. Sujitha b, C. Ganesh Kumar b a b

Centre for Lipid Research, CSIR-Indian Institute of Chemical Technology, Tarnaka, Hyderabad 500007, India Chemical Biology Laboratory, CSIR-Indian Institute of Chemical Technology, Tarnaka, Hyderabad 500007, India

a r t i c l e i n f o

a b s t r a c t

Article history: Received 31 May 2013 Received in revised form 28 June 2013 Accepted 1 July 2013 Available online 12 July 2013

The first total synthesis of clavaminol-G (1) and 1-aminoundecan-2-ol (2) has been achieved from 10undecenoic acid using epoxidation, regioselective azidolysis and in situ detosylation and reduction reactions as key steps. The methodology is extended for the synthesis of 1-aminoundecan-2-ol derivatives; namely, methyl 11-amino-10-hydroxyundecanoate (3), 11-amino-10-hydroxyundecanoic acid (4) and 11aminoundecan-1,10-diol (5). Among these, 1-aminoundecan-2-ol (2) exhibited good antimicrobial activity and promising cytotoxicity towards HeLa, MDA-MB-231, MCF-7 and A549 cell lines with IC50 values of 4.36, 4.02, 3.88 and 6.78 mM, respectively. Compound 3 exhibited good activity against HeLa cells (IC50 ¼ 3.59 mM), while compound 5 showed moderate activity towards HeLa and A549 cell lines. Clavaminol G (1) and compound 4 showed no activity towards all the cell lines. Ó 2013 Elsevier Masson SAS. All rights reserved.

Keywords: Clavaminol-G 1-Aminoundecan-2-ol Epoxidation Azidolysis Cytotoxic activity Antimicrobial activity

1. Introduction Amino alcohol functional groups are often found in many bioactive compounds with significant applications in synthetic and pharmaceutical chemistry. Different compounds containing amino alcohol moiety have been synthesized for use in various diseases [1]. Among the numerous amino alcohols, clavaminols AeN are a new class of 2-amino-3-alkanols with a wide range of bioactivities, such as anti-inflammatory, antibacterial, anticancer, anti-protozoal, anathematic and antifungal activities [2]. Structurally, these compounds are related to the widely distributed amphiphilic sphingosine derivatives. Due to the wide spectrum of biological activities, the clavaminols family has attracted increased attention by both synthetic organic chemists and biologists. Recently, marine organisms and ascidians (tunicates) have been identified as an enriched bioresource for these compounds. Searching for new bioactive compounds from marine origin, Aiello et al. reported clavaminols AeF [3], with cytotoxic properties against A549, T47D and AGS cell lines. Recently, Aiello et al. [4] isolated six new amino alcohols, clavaminols GeN from the Mediterranean ascidian

* Corresponding author. Tel.: þ91 40 27191845; fax: þ91 40 27193370. E-mail address: [email protected] (B.L.A. Prabhavathi Devi). 0223-5234/$ e see front matter Ó 2013 Elsevier Masson SAS. All rights reserved. http://dx.doi.org/10.1016/j.ejmech.2013.07.001

Clavelina phlegrea. Clavaminol G (1) and its hydrolyzed product 1aminoundecan-2-ol (2) are the marine-derived bioactive compounds isolated by Aiello and co-workers from the Mediterranean ascidian C. phlegrea. Clavaminol G and 1-aminoundecan-2-ol are the sphingoid-type bases, which contains a long saturated C11 alkyl chain with 1,2-aminoalcohol moiety. These naturally-occurring bioactive compounds exhibited moderate to good cytotoxicity against A549 (lung carcinoma) and AGS (gastric carcinoma) cell lines [4]. Due to these interesting structural pattern and bioactivities, the synthesis of clavaminol G and 1-aminoundecan-2-ol is considered important for the organic chemists. In continuation to our previous work [5] on the construction of bioactive naturallyoccurring compounds, in the present study, we synthesized clavaminol G (1) and 1-aminoundecan-2-ol (2) from 10-undecenoic acid, which is derived from a renewable feedstock, castor oil. In addition, we also synthesized the compounds methyl 11-amino-10hydroxyundecanoate (3), 11-amino-10-hydroxyundecanoic acid (4) and 11-aminoundecan-1,10-diol (5), the derivatives of 1aminoundecan-2-ol (2) with eCOOCH3, eCOOH and eOH terminal functional groups, respectively. All these synthesized compounds, 1e5 were further evaluated for their biological activities. To the best of our knowledge, this is the first report on the total synthesis and biological evaluation of clavaminol G (1) and 1aminoundecan-2-ol (2).

T. Vijai Kumar Reddy et al. / European Journal of Medicinal Chemistry 67 (2013) 384e389

2. Results and discussion 2.1. Chemistry Our retrosynthetic analysis of compounds 1 and 2 is illustrated in Scheme 1. As indicated, compounds 1 and 2 could be synthesized from the azido tosylate 10, which in turn could be obtained from the epoxy alcohol 8. Compound 8 would be derived from readily available 10-undecenoic acid 6. The synthesis of clavaminol G (1) and 1-aminoundecan-2-ol (2) (Scheme 2) was initiated with commercially available fatty acid namely, 10-undecenoic acid 6 which was converted to alcohol 7 in high yield (97%) by lithium aluminum hydride (LAH) reduction [5,6]. The alcohol 7 on epoxidation [7] with meta-chloroperoxybenzoic acid (m-CPBA) in dichloromethane (DCM) at room temperature gave epoxy alcohol 8 in about 87% yield [8]. Azidolysis [7c,9] of 8 with sodium azide in C2H5OH:H2O (5:1) in presence of NH4Cl furnished 11-azidoundecan-1,10-diol (9) as a viscous liquid in 92.5% yield. The 13C NMR spectrum of compound 9, showed signals for CH2 group of C-11 at d 56.83 ppm and CH group of C-10 at d 70.56 ppm [7b]. Tosylation [5] of compound 9 with 1.1 equiv of tosyl chloride in dry DCM and in the presence of triethylamine at 0  C produced azido tosylate 10 in 71% yield. The synthesis of 1aminoundecan-2-ol (2) was completed in one-pot from azido tosylate 10 by LAH reduction [5,10] in 69% yield, by involving simultaneous reduction of eN3 to eNH2 and detosylation. Finally, the total synthesis of clavaminol G (1) was achieved from compound 2 by selective acetylation [11] of amine group with acetic anhydride (Ac2O) in dry tetrahydrofuran (THF) at reflux temperature in 75.5% yield. The spectroscopic data of clavaminol G was found to be identical to those of the natural product [4]. The overall yield of the clavaminol G obtained was 28.9% after six steps. We next turned our attention towards the synthesis of derivatives of 1-aminoundecan-2-ol (2) namely, methyl 11-amino-10hydroxyundecanoate (3), 11-amino-10-hydroxyundecanoic acid (4) and 11-aminoundecan-1,10-diol (5). The synthesis was performed as shown in Scheme 3. Initially, methyl undec-10-enoate 11 was prepared by esterification [12] of 10-undecenoic acid 6 with 2% H2SO4/CH3OH at reflux temperature in excellent yield (98%). Epoxidation [7a,13] of 11 with m-CPBA in DCM at room temperature afforded epoxy compound 12 in 87.5% yield. Treatment of the epoxide 12 with sodium azide in C2H5OH:H2O (5:1) and in the presence of NH4Cl gave methyl 11-azido-10-hydroxyundecanoate 13 in 93% yield as a pale yellow oil [7b]. Reduction of the azide group of 13 with 10% Pd/C under hydrogen atmosphere in methanol [7b,10], furnished compound 3 in good yield (83.5%), which was subsequently subjected to hydrolysis [14] to give compound 4 in 90.7% yield [15]. Whereas, compound 5 was obtained in 95% yield from one-pot reduction of compound 13 with LAH [5,6].

385

MDA-MB-231, MCF-7 and A549. Based on the cytotoxicity results shown in Table 1, it was observed that 1-aminoundecan-2-ol (2) exhibited an excellent cytotoxicity against all four-tumor cell lines, namely HeLa, MDA-MB-231, MCF-7 and A549 with IC50 values of 4.36, 4.02, 3.88 and 6.78 mM, respectively. 1-Aminoundecan-2-ol derivative 3 with terminal ester moiety showed good activity against HeLa cells with IC50 value of 3.59 mM, moderate activity against A549 and MCF-7 cells with IC50 values of 7.89, 10.19 mM, respectively and weak activity towards MDA-MB-231 cells with IC50 value of 29.79 mM. Compound 5 with alcohol functionality showed moderate activity towards HeLa and A549 cell lines. However, clavaminol G (1) and compound 4 with terminal acid functionality did not show any activity towards all the tested tumor cell lines. 2.2.2. Antimicrobial activity Based on the antimicrobial results for all synthesized compounds 1e5, only 1-aminoundecan-2-ol (2) exhibited good antibacterial activity (MIC values of 18.75 mg/mL) against the various Gram-positive (Micrococcus luteus MTCC 2470, Bacillus subtilis MTCC 121, Staphylococcus aureus MTCC 96 and S. aureus MLS16 MTCC 2940) and Gram-negative (Escherichia coli MTCC 739, Pseudomonas aeruginosa MTCC 2453 and Klebsiella planticola MTCC 530) bacterial strains and the MIC values were comparable to those observed against the standard drug, neomycin. Similarly, the antifungal results against different Candida strains as shown in Table 2. 3. Conclusion In conclusion, we have developed a simple route for the total synthesis of a natural bioactive compounds clavaminol G (1) and 1aminoundecan-2-ol (2) starting from commercially available 10undecenoic acid. The key transformations involved in the synthesis are epoxidation, azidolysis and one-pot reduction of azido tosylate 10. All the steps involved in the present synthesis are high yielding and the applied reagents are readily available. This proposed synthetic route is straightforward, flexible and effective, as the raw material comes from renewable sources. Among the synthesized compounds, compound 2 with free amino alcohol moiety exhibited potent cytotoxic activity towards all the four-tumor cell lines of HeLa, MDA-MB-231, MCF-7 and A549 cells. Interestingly, compound 3which is derivative of 1-aminoundecan-2-ol by the presence of an extra ester functionality, showed significant cytotoxic activity against HeLa cells (IC50 ¼ 3.59 mM). Whereas compound 5 with eOH terminal functional group was indeed cytotoxic, only in HeLa and A549 cells, while compounds 1 and 4 were completely inactive towards all the four cell lines, indicating that free NH2 and OH functional groups are critical for the cytotoxic activity. In addition, 1-aminoundecan-2-ol (2) showed very good antimicrobial and antifungal activities. 4. Experimental section

2.2. Biological evaluation 4.1. General experimental 2.2.1. Cytotoxicity assay The cytotoxicity evaluation of all the synthesized compounds 1e 5 was carried out on four human tumor cell lines namely, HeLa,

OH ()

NHR1

OH 2

7

1, 2

()

R

N3

All reagents used were of analytical grade and were used as obtained from different commercially sources without any further

O

O

8

10

OTs

()

8

OH

8

()

8

6

R1 = COCH3 , R2 = CH3, clavaminol G (1); R1 = H, R2 = CH3, 1-aminoundecan-2-ol (2) Scheme 1. Retrosynthetic analysis of clavaminol G (1) and 1-aminoundecan-2-ol (2).

OH

386

T. Vijai Kumar Reddy et al. / European Journal of Medicinal Chemistry 67 (2013) 384e389

O ()

8

i

OH

()

6

8

N3

()

OH

OH

iv

()

8

N3

9

OTs

iii

OH

8

8

7

OH ()

8

O

ii

OH

OH

v

() NH2

10

OH

vi

()

7

NHAc

7

1

2

Reagents and conditions: i) LiAlH4, dry THF, 0 ºC to rt, 30 min, 97%; ii) m-CPBA, DCM, room temperature, 4 h, 87.1%; iii) NaN3, NH4Cl, C2H5OH:H2O (5:1), reflux, 24 h, 92.5%; iv) p-TsCl, Et3N, DMAP, dry DCM, 0 ºC, 5 h, 71%; v) LiAlH4, dry THF, 0 ºC to room temperature, 8 h, 69%; vi) Ac2O, dry THF, room temperature to reflux, 5 h, 75.5%. Scheme 2. Synthesis of clavaminol G (1) and 1-aminoundecan-2-ol (2).

dried over anhydrous Na2SO4 and evaporated under reduced pressure. The obtained residue was purified by column chromatography (4% ethyl acetate in hexane) to afford (7) as a colorless oil (2.69 g, 97%). 1H NMR (CDCl3, 300 MHz): d 5.68e5.83 (m, 1H, H-10), 4.87e4.99 (m, 2H, H-11), 3.59 (t, J ¼ 6.7 Hz, 2H, H-1), 1.98e2.07 (m, 2H, H-9), 1.49e1.59 (m, 2H, H-2), 1.24e1.41 (m, 12H, H-3, H-4, H-5, H-6, H-7, H-8). IR (neat, cm1) n: 3370 (OH), 3076 (]CHaliph.), 2926, 2854 (CHaliph.), 1639 (C]C). ESI-MS m/z: 171 [M þ H]þ.

purification. All dry reactions were carried out under nitrogen environment in oven-dried glassware using standard gas-light syringes, cannulas, and septa. Reactions were carried out using anhydrous solvents and were monitored on silica gel TLC plates (coated with TLC grade silica gel, obtained from Merck) employing iodine vapors for detection of spots. Column chromatography was performed over silica gel (100e200 mesh) procured from Qualigens (India) using freshly distilled solvents. Mass spectra were recorded using electron spray ionization-mass spectrometry (ESI-MS). IR spectra were recorded on a PerkineElmer FT-IR Spectrum BX. 1H NMR and 13C NMR spectra were recorded on Bruker UXNMR (operating at 300 MHz, 500 MHz for 1H and 75 MHz, 125 MHz for 13 C NMR) spectrometer using CDCl3. Chemical shifts d are reported relative to TMS (d ¼ 0.0) as an internal standard. All spectra were recorded at 25  C.

4.1.2. 9-(Oxiran-2-yl)nonan-1-ol (8) [8] m-CPBA (2.44 g, 14.11 mmol) was added to a stirred solution of 10-undecen-1-ol (7) (2.0 g, 11.76 mmol) in DCM (10 mL) at room temperature. The mixture was stirred for 4 h. Then DCM was added and the organic phase was successively washed with saturated solution of NaHSO3, NaHCO3 and NaCl. The combined organic phases were dried over anhydrous Na2SO4 and evaporated under reduced pressure. The obtained residue was purified by column chromatography (10% ethyl acetate in hexane) afforded pure 9(oxiran-2-yl)nonan-1-ol (8) (1.90 g, 87.1%) as a colorless liquid. 1H NMR (CDCl3, 300 MHz): d 3.63 (t, J ¼ 6.6 Hz, 2H, H-1), 2.87e2.95 (m, 1H, H-11a), 2.72e2.78 (m, 1H, H-10), 2.46 (dd, J ¼ 4.9 Hz, 2.6 Hz, 1H, H-11b), 1.68 (br s, 1H, eOH), 1.41e1.62 (m, 6H, H-2, H-3, H-9), 1.24e 1.39 (m, 10H, H-4, H-5, H-6, H-7, H-8). 13C NMR (CDCl3, 125 MHz):

4.1.1. 10-Undecen-1-ol (7) [5,6] 10-Undecenoic acid (3.0 g, 16.30 mmol) in dry THF (15 mL) was added dropwise to a stirred suspension of LiAlH4 (0.90 g, 24.45 mmol) in dry THF (20 mL) at 0  C and the reaction mixture was stirred for 30 min at room temperature. The reaction mixture was quenched with ethyl acetate. The solution was filtered and the organic layer was washed with distilled water and brine solution,

O ()

8

OH

O

i

()

6

()

OH

5

8

()

11

OH NH 2

OMe

8

OH

vi

() N3

O

O

ii

OMe

8

OH

iii

() N3

12 O

8

OMe

iv

13

O

8

OMe

13

OH () NH 2

3

O

8

OMe

v

OH () NH 2

O

8

OH

4

Reagents and conditions: i) 2% H2SO4/CH3OH, reflux, 4 h, 98%; ii) m-CPBA, DCM, room temperature, 4 h, 87.5%; iii) NaN3, NH4Cl, C2H5OH:H2O (5:1), reflux, 24 h, 93.7%; iv) H2, 10% Pd-C, CH3OH, room temperature, 4 h, 83.5%; v) 10% KOH/C2H5OH, reflux, 2 h, 90.7%; vi) LiAlH4, dry THF, 0 ºC to room temperature, 5 h, 95%. Scheme 3. Synthesis of methyl 11-amino-10-hydroxyundecanoate (3), 11-amino-10-hydroxyundecanoic acid (4) and 11-aminoundecan-1,10-diol (5).

T. Vijai Kumar Reddy et al. / European Journal of Medicinal Chemistry 67 (2013) 384e389 Table 1 Cytotoxicity testing against four human cancer cell lines for compounds 1e5. Comp. No.

1 2 3 4 5 Doxorubicin

IC50 values (in mM) HeLa

MDA-MB-231

MCF-7

A549

e 4.36 3.59 e 8.79 0.45

e 4.02 29.79 e e 0.50

e 3.88 10.19 e e 1.05

e 6.78 7.89 e 16.19 1.21

e: No activity, HeLa: human cervical cancer cell line, MDA-MB-231: Human breast adenocarcinoma cell line, MCF-7: human breast adenocarcinoma cell line, A549: human alveolar adenocarcinoma cell line.

d 62.85, 52.37, 47.06, 32.68, 32.38, 29.38 (2C), 29.31 (2C), 25.87, 25.64. IR (neat, cm1) n: 3393 (OH), 2927, 2855 (CHaliph.), 1258, 834 (CeOeCoxirane). ESI-MS m/z: 186 [M þ H]þ.

4.1.3. 11-Azidoundecan-1,10-diol (9) NaN3 (3.25 g, 50 mmol) and NH4Cl (1.16 g, 22.0 mmol) were added to a stirred solution of 9-(oxiran-2-yl)nonan-1-ol (1.86 g, 10.0 mmol) in ethanolewater (5:1 v/v, 20 mL) at room temperature. The reaction mixture was refluxed for 24 h. The solvent was evaporated and 10 mL of distilled water was added. Then the reaction mixture was extracted with CHCl3 (3  15 mL). The combined organic layers were dried over anhydrous Na2SO4 and evaporated under reduced pressure. The obtained residue was purified by column chromatography (3% methanol in chloroform) afforded (9) (2.12 g, 92.5%) as a viscous liquid. 1H NMR (CDCl3, 300 MHz) d: 3.71e3.81(m, 1H, H-10), 3.64 (t, J ¼ 6.7 Hz, 2H, H-1), 3.37 (dd, J ¼ 12.0 Hz, 3.0 Hz, 1H, H-11a), 3.24 (dd, J ¼ 12.0 Hz, 7.5 Hz, 1H, H-11b), 2.07 (br s, 1H, eOH), 1.70 (br s, 1H, eOH), 1.52e1.62 (m, 2H, H-2), 1.42e1.50 (m, 2H, H-9), 1.23e1.39 (m, 12H, H-3, H-4, H-5, H-6, H-7, H-8). 13C NMR (CDCl3, 75 MHz) d: 70.56, 62.59, 56.83, 34.16, 32.47, 29.32, 29.26, 29.21, 25.83, 25.55, 25.27. IR (neat, cm1) n: 3363 (OH), 2928, 2855 (CHaliph.), 2101(Nþ^N). ESI-MS m/z: 252 [M þ Na]þ. 4.1.4. 11-Azido-10-hydroxyundecyl-4-methylbenzenesulfonate (10) Anhydrous Et3N (1.93 mL, 13.88 mmol) was added dropwise to an ice cooled solution of azido diol 9 (2.12 g, 9.25 mmol) in dry CH2Cl2 (20 mL) followed by addition of p-TsCl (1.93 g, 10.15 mmol) and a catalytic amount of 4-dimethylaminopyridine. The reaction mixture was stirred at 0  C for 5 h. The mixture was diluted with distilled water (15 mL) and extracted with CH2Cl2 (2  20 mL). The combined organic layers were washed with distilled water (20 mL), brine solution (20 mL) and dried over anhydrous Na2SO4. The

Table 2 Antifungal activity of 1-aminoundecan-2-ol (2). Test strain

MIC (mg/mL) Compound (2)

Fluconazole

Miconazole

Candida albicans MTCC 183 Candida albicans MTCC 854 Candida albicans MTCC 1637 Candida albicans MTCC 3017 Candida albicans MTCC 3018 Candida albicans MTCC 3958 Candida albicans MTCC 4748 Candida albicans MTCC 7315 Candida parapsilosis MTCC 1744 Candida glabrata MTCC 3019 Candida aaseri MTCC 1962 Issatchenkia orientalis MTCC 3020 Issatchenkia hanoiensis MTCC 4755

18.75 18.75 18.75 18.75 18.75 18.75 18.75 18.75 18.75 18.75 18.75 18.75 18.75

37.5 37.5 75.0 75.0 37.5 75.0 37.5 37.5 18.75 75.0 37.5 150 75.0

9.37 9.37 9.37 9.37 9.37 9.37 9.37 9.37 9.37 9.37 9.37 9.37 9.37

387

solvent was removed under reduced pressure and the obtained residue was purified by column chromatography (5% ethyl acetate in hexane) which afforded (10) (2.51 g, 71%) as a colorless gum. 1H NMR (CDCl3, 300 MHz): d 7.78 (d, J ¼ 8.3 Hz, 2H, ArH), 7.34 (d, J ¼ 8.1 Hz, 2H, ArH), 4.01 (t, J ¼ 6.4 Hz, 2H, H-1), 3.71e3.81 (m, 1H, H-10), 3.37 (dd, J ¼ 12.2 Hz, 3.2 Hz, 1H, H-11a), 3.24 (dd, J ¼ 12.2 Hz, 7.3 Hz, 1H, H-11b), 2.45 (s, 3H, ArCH3), 1.56e1.72 (m, 2H, H-2), 1.40e 1.50 (m, 2H, H-9), 1.17e1.37 (m, 12H, H-3, H-4, H-5, H-6, H-7, H-8). 13 C NMR (CDCl3, 75 MHz): d 144.56, 133.10, 129.72 (2C), 127.76 (2C), 70.71, 70.62, 57.02, 34.19, 29.31, 29.19, 29.13, 28.74, 28.70, 25.29, 25.19, 21.54. IR (neat, cm1) n: 3536 (OH), 3032 (CHarom.), 2929, 2856 (CHaliph.), 2100 (Nþ^N), 1598 (C]Carom.), 1357 (O]S]O). ESI-MS m/z: 406 [M þ Na]þ. 4.1.5. 1-Aminoundecan-2-ol (2) [4] 11-Azido-10-hydroxyundecyl-4-methylbenzenesulfonate (0.24 g, 0.62 mmol) in dry THF (5 mL) was added dropwise to a stirred solution of LiAlH4 (0.18 g, 4.98 mmol) in dry THF (15 mL) at 0  C. The reaction mixture allowed to warm to room temperature and stirred for 8 h. The reaction mixture was quenched by the addition of distilled water (5 mL). The mixture was extracted with ethyl acetate (3  10 mL), washed with distilled water (10 mL), brine solution (10 mL) and dried over anhydrous Na2SO4. The solvent was removed under reduced pressure and the obtained residue was purified by column chromatography (20% methanol in chloroform), which afforded (2) (0.08 g, 69%) as a white solid. Mp: 103e105  C; 1H NMR (CDCl3 þ CD3OD, 300 MHz): d 3.45e3.57 (m, 1H, H-2), 2.72 (dd, J ¼ 13.0 Hz, 2.8 Hz, 1H, H-1a), 2.53 (dd, J ¼ 13.0 Hz, 8.4 Hz, 1H, H-1b), 1.36e1.47 (m, 2H, H-3), 1.17e1.34 (br m, 14H, H-4, H-5, H-6, H-7, H-8, H-9, H-10), 0.88 (t, J ¼ 6.6 Hz, 3H, H11). 13C NMR (CDCl3 þ CD3OD, 75 MHz): d 71.48, 46.57, 34.47, 31.49, 29.28, 29.18 (2C), 28.90, 25.22, 22.24, 13.49. IR (KBr, cm1) n: 3397 (OH), 3207 (NH2), 2917, 2850 (CHaliph.). ESI-MS m/z: 188 [M þ H]þ. HRMS calcd for C11H26NO [M þ H]þ 188.2008, found 188.2006. 4.1.6. Clavaminol G [N-(2-hydroxyundecyl)acetamide] (1) [4] Acetic anhydride (0.04 mL, 0.49 mmol) was added to a stirred solution of (2) (0.08 g, 0.41 mmol) in dry THF (10 mL) and the resulting mixture was stirred at room temperature for 1 h. After 1 h, stirring was continued for additional 5 h at 65  C. The reaction mixture was diluted with distilled water (10 mL) and ethyl acetate (10 mL). The organic phase was washed with brine solution, dried over anhydrous Na2SO4 and evaporated under reduced pressure. The obtained residue was purified by column chromatography (3% methanol in chloroform) afforded pure N-(2-hydroxyundecyl) acetamide (1) (0.07 g, 75.5%) as white solid. Mp: 89e91  C; 1H NMR (CDCl3, 500 MHz): d 5.89e5.98 (m, 1H, eNH), 3.67e3.74 (m, 1H, H2), 3.45e3.51 (ddd, J ¼ 14.3 Hz, 6.6 Hz, 3.3 Hz, 1H, H-1a), 3.06e3.14 (ddd, J ¼ 13.2 Hz, 7.7 Hz, 5.5 Hz, 1H, H-1b), 2.43 (br s, 1H, eOH), 2.01 (s, 3H, NHCOCH3), 1.40e1.48 (m, 2H, H-3), 1.22e1.34 (m, 14H, H-4, H-5, H-6, H-7, H-8, H-9, H-10), 0.87 (t, J ¼ 6.6 Hz, 3H, H-11). 13C NMR (CDCl3, 75 MHz): d 171.15, 71.27, 45.82, 35.02, 31.83, 29.51 (3C), 29.25, 25.46, 23.14, 22.62, 14.05. IR (KBr, cm1) n: 3408 (OH), 3281 (NH), 2917, 2849 (CHaliph.), 1628 (C]O), 1587 (NH d). ESI-MS m/z: 230 [M þ H]þ. HRMS calcd for C13H28NO2 [M þ H]þ 230.2114, found 230.2108. 4.1.7. Methyl undec-10-enoate (11) [12] A solution of 10-undecenoic acid (6) (5 g, 27.17 mmol) in 2% H2SO4/CH3OH (50 mL), was refluxed for 4 h. The reaction mixture was cooled to room temperature and extracted with ethyl acetate (2  50 mL). The combined organic phases were dried over anhydrous Na2SO4 and evaporated under reduced pressure. The obtained residue was purified by column chromatography (100% hexane) afforded pure methyl undec-10-enoate (5.27 g, 98%) as a

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colorless oil. 1H NMR (CDCl3, 300 MHz): d 5.68e5.82 (m, 1H, H-10), 4.87e4.99 (m, 2H, H-11), 3.64 (s, 3H, eOCH3), 2.26 (t, J ¼ 7.5 Hz, 2H, H-2), 1.98e2.07 (q, 2H, H-9), 1.55e1.65 (m, 2H, H-3), 1.25e1.41 (m, 10H, H-4, H-5, H-6, H-7, H-8). IR (neat, cm1) n: 3076 (]CHaliph.), 2927, 2855 (CHaliph.), 1742 (C]O), 1640 (C]C). ESI-MS m/z: 199 [M þ H]þ. 4.1.8. Methyl 9-(oxiran-2-yl)nonanoate (12) [13] m-CPBA (4.19 g, 24.24 mmol) was added to a stirred solution of methyl undec-10-enoate (4.0 g, 20.2 mmol) in DCM (20 mL) at room temperature. The mixture was stirred for 4 h. Then DCM was added and the organic phase was successively washed with saturated solution of NaHSO3, NaHCO3 and brine solution. The combined organic phases were dried over anhydrous Na2SO4 and evaporated under reduced pressure. The obtained residue was purified by column chromatography (5% ethyl acetate in hexane) afforded pure methyl 9-(oxiran-2-yl)nonanoate (12) (3.78 g, 87.5%) as a colorless liquid. 1H NMR (CDCl3, 300 MHz): d 3.64 (s, 3H, e OCH3), 2.82 (br m, 1H, H-10), 2.66e2.69 (m, 1H, H-11a), 2.39 (dd, J ¼ 4.5 Hz, 2.2 Hz, 1H, H-11b), 2.26 (t, J ¼ 7.5 Hz, 2H, H-2), 1.54e1.67 (m, 2H, H-3), 1.40e1.53 (m, 4H, H-4, H-9), 1.26e1.37 (m, 8H, H-5, H6, H-7, H-8). IR (neat, cm1) n: 2927, 2855 (CHaliph.), 1742 (C]O), 1172, 834(CeOeCoxirane.). ESI-MS m/z: 215 [M þ H]þ. 4.1.9. Methyl 11-azido-10-hydroxyundecanoate (13) [7b] NaN3 (3.25 g, 50 mmol) and NH4Cl (1.16 g, 22.0 mmol) were added to a stirred solution of methyl 9-(oxiran-2-yl)nonanoate (2.14 g, 10.0 mmol) in ethanolewater (5:1 v/v, 20 mL) at room temperature. The reaction mixture was refluxed for 24 h. The solvent was evaporated and 10 mL of distilled water was added. Then the reaction mixture was extracted with CHCl3 (3  15 mL). The combined organic layers were dried over anhydrous Na2SO4 and evaporated under reduced pressure. The obtained residue was purified by column chromatography (3% methanol in chloroform) afforded (13) (2.41 g, 93.7%) as a pale yellow oil. 1H NMR (CDCl3, 300 MHz): d 3.68e3.74 (m, 1H, H-10), 3.64 (s, 3H, eOCH3), 3.32 (dd, J ¼ 11.7 Hz, 2.9 Hz, 1H, H-11a), 3.21 (dd, J ¼ 11.7 Hz, 6.8 Hz, 1H, H11b), 2.27 (t, J ¼ 7.8 Hz, 2H, H-2), 1.57e1.64 (m, 2H, H-3), 1.41e1.47 (m, 2H, H-9), 1.27e1.34 (m, 10H, H-4, H-5, H-6, H-7, H-8). 13C NMR (CDCl3, 75 MHz): d 174.28, 70.60, 56.82, 51.29, 34.10, 33.86, 29.22, 29.06, 28.91, 28.85, 25.19, 24.68. IR (neat, cm1) n: 3363 (OH), 2928, 2855 (CHaliph.), 2101 (Nþ^N), 1742 (C]O). ESI-MS m/z: 280 [M þ Na]þ. 4.1.10. Methyl 11-amino-10-hydroxyundecanoate (3) [7b] A 10% PdeC (0.05 g) was added to a stirred solution of (13) (0.50 g, 1.94 mmol) in methanol (20 mL). The reaction mixture was stirred for 4 h at room temperature under the pressure of hydrogen balloon, the reaction mixture was filtered through Celite and the filtrate was evaporated under reduced pressure. The obtained residue was purified by column chromatography (10% methanol in chloroform) afforded (3) (0.37 g, 83.5%) as a white solid. Mp: 99e 102  C; 1H NMR (CDCl3, 300 MHz): d 5.03e5.28 (br m, 2H, eNH2), 3.69e3.80 (m, 1H, H-10), 3.66 (s, 3H, eOCH3), 2.94 (dd, J ¼ 12.0 Hz, 2.2 Hz, 1H, H-11a), 2.72 (dd, J ¼ 12.8 Hz, 9.8 Hz, 1H, H-11b), 2.30 (t, J ¼ 7.5 Hz, 2H, H-2), 1.56e1.66 (m, 2H, H-3), 1.38e1.47 (m, 2H, H-9), 1.24e1.32 (m, 10H, H-4, H-5, H-6, H-7, H-8). 13C NMR (CDCl3, 75 MHz): d 174.27, 68.34, 51.45, 45.42, 35.00, 34.05, 29.51, 29.36, 29.22, 29.10, 25.48, 24.90; IR (KBr, cm1) n: 3477 (OH), 3237 (NH2), 2928, 2849 (CHaliph.), 1742 (C]O). ESI-MS m/z: 232 [M þ H]þ. HRMS calcd for C12H26NO3 [M þ H] þ 232.1907, found 232.1896. 4.1.11. 11-Amino-10-hydroxyundecanoic acid (4) [15] A solution of (3) (0.23 g, 1 mmol) in 10% ethanolic KOH (3 mL) was refluxed for 2 h. After evaporation of the solvent, the residue

was dissolved in distilled water (1 mL), and the resulting solution was acidified with 1 N HCl with ice-bath cooling. The precipitated solid was filtered, washed with distilled water, and dried under vacuum to give 11-amino-10-hydroxyundeacanoic acid (4) (0.19 g, 90.7%) as white solid. Mp: 198e200  C; 1H NMR (D2O þ CD3OD, 300 MHz): d 3.70e3.81 (br m, 1H, H-10), 3.04 (dd, J ¼ 13.0 Hz, 3.0 Hz, 1H, H-11a), 2.78 (dd, J ¼ 13.0 Hz, 9.6 Hz, 1H, H-11b), 2.10 (t, J ¼ 7.3 Hz, 2H, H-2), 1.85 (br s, 1H, eOH), 1.37e1.54 (m, 4H, H-3, H9), 1.19e1.30 (m, 10H, H-4, H-5, H-6, H-7, H-8). IR (KBr, cm1) n: 3430 (OH), 3243 (NH2), 2916, 2848 (CHaliph.), 1704 (C]O). ESI-MS m/z: 218 [M þ H]þ. HRMS calcd for C11H24NO3 [M þ H]þ 218.1750, found 218.1741. 4.1.12. 11-Aminoundecan-1,10-diol (5) A solution of (13) (0.26 g, 1.0 mmol) in dry THF (5 mL) was added dropwise to a stirred solution of LiAlH4 (0.18 g, 5.0 mmol) in dry THF (15 mL) at 0  C. The reaction mixture was allowed to warm to room temperature and stirred for 5 h. The reaction mixture was quenched by the addition of distilled water (5 mL). The mixture was extracted with ethyl acetate (3  10 mL), washed with distilled water (10 mL), brine solution (10 mL) and dried over anhydrous Na2SO4. The solvent was removed under reduced pressure and the obtained residue was purified by column chromatography (20% methanol in chloroform) to afford (5) (0.19 g, 95%) as a white solid. Mp: 87e89  C; 1H NMR (CD3OD þ CDCl3, 500 MHz): d 3.53 (t, J ¼ 6.65 Hz, 2H, H-1), 3.30e3.32 (m, 1H, H-10), 2.73 (dd, J ¼ 13.3 Hz, 3.8 Hz, 1H, H-11a), 2.56 (dd, J ¼ 13.3 Hz, 8.5 Hz, 1H, H-11b), 1.49e1.56 (m, 2H, H-2), 1.39e1.48 (m, 2H, H-9), 1.29e1.38 (m, 12H, H-3, H-4, H-5, H-6, H-7, H-8). 13C NMR (CDCl3, 125 MHz): d 70.73, 62.13, 46.33, 34.56, 32.23, 29.28, 29.19, 29.16, 29.10, 25.45, 25.24. IR (KBr, cm1) n: 3491 (OH), 3218(NH2), 2924, 2895 (CHaliph.). ESI-MS m/z: 204 [M þ H]þ. HRMS calcd for C11H26NO2 [M þ H]þ 204.1958, found 204.1954. 4.2. Biological assays 4.2.1. Cytotoxicity assay Cytotoxicity of the compounds was determined based on the measurement of in vitro growth inhibition of tumor cell lines in 96 well plates by cell-mediated reduction of tetrazolium salt to water insoluble formazan crystals using doxorubicin as a standard. The cytotoxicity was assessed against a panel of four different human tumor cell lines: A549 derived from human alveolar adenocarcinoma epithelial cells (ATCC No. CCL-185), HeLa derived from human cervical cancer cells (ATCC No. CCL-2), MDA-MB-231 derived from human breast adenocarcinoma cells (ATCC No. HTB-26) and MCF7 derived from human breast adenocarcinoma cells (ATCC No. HTB-22) using the MTT assay [16]. The IC50 values (50% inhibitory concentration) were calculated from the plotted absorbance data for the doseeresponse curves. IC50 values (in mM) are expressed as the average of two independent experiments. 4.2.2. Antimicrobial activity The antimicrobial activity of the synthesized compounds was determined using well diffusion method [17] against different pathogenic strains procured from the Microbial Type Culture Collection and Gene Bank (MTCC), CSIR-Institute of Microbial Technology, Chandigarh, India. The pathogenic strains were seeded on the surface of the media Petri plates, containing MullereHinton agar with 0.1 mL of previously prepared microbial suspensions individually containing 1.5  108 CFU/mL (equal to 0.5 McFarland). Wells of 6.0 mm diameter were prepared in the media plates using a cork borer and the synthesized compounds at a dose range of 1.4e 300 mg was added in each well under sterile conditions in a laminar air flow chamber. Standard antibiotic solutions of neomycin

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(bacterial strains), fluconazole and miconazole (Candida strains) at a dose range of 1.4e300 mg, served as positive controls, while the well containing DMSO served as negative control. The plates were incubated for 24 h at 30  C and the well containing the least concentration showing the inhibition zone is considered as the minimum inhibitory concentration. All experiments were carried out in duplicates and mean values are represented. Acknowledgments The authors acknowledge the financial support from the Council of Scientific and Industrial Research (CSIR), New Delhi, India, in the form of Senior Research Fellowships (SRF) to T.V.K. Reddy and P. Sujitha. Appendix A. Supplementary data Supplementary data associated with this article can be found in the online version, at http://dx.doi.org/10.1016/j.ejmech.2013.07.001. References [1] M.L. Ferreira, T.R.A. Vasconcelos, E.M. de Carvalho, M.C.S. Lourenco, S.M.S.V. Wardell, J.L. Wardell, V.F. Ferreira, M.V.N. de Souza, Synthesis and antitubercular activity of novel Schiff bases derived from D-mannitol, Carbohydr. Res. 344 (2009) 2042e2047. [2] (a) N.K. Gulavita, P.J. Scheuer, Two epimeric aliphatic amino alcohols from a sponge Xestospongia sp, J. Org. Chem. 54 (1989) 366e369; (b) C. Jimenez, P. Crews, Novel marine sponge amino acids, 10. Xestoaminols from Xestospongia sp, J. Nat. Prod. 53 (1990) 978e982; (c) C. Devijver, M. Salmoun, D. Daloze, J.C. Braekman, W.H. De Weerdt, M.J. De Kluijver, R. Gomez, (2R,3R,7Z)-2-Aminotetradec-7-ene-1,3-diol, a new amino alcohol from the Caribbean sponge Haliclona vansoesti, J. Nat. Prod. 63 (2000) 978e980; (d) R.J. Clark, M.J. Garson, J.N.A. Hooper, Antifungal alkyl amino alcohols from the tropical marine sponge Haliclona n. sp. J. Nat. Prod. 64 (2001) 1568e1571; (e) M.H. Kossuga, J.B. MacMillan, E.W. Rogers, T.F. Molinski, G.G.F. Nascimento, R.M. Rocha, R.G.S. Berlinck, (2S,3R)-2-Aminododecan-3-ol, a new antifungal agent from the, ascidian Clavelina oblonga, J. Nat. Prod. 67 (2004) 1879e1881; (f) D.J. Newman, G.M. Cragg, Natural products as sources of new drugs over the last 25 years, J. Nat. Prod. 70 (2007) 461e467; (g) A. Casapullo, A. Fontana, G. Cimino, Coriacenins: a new class of long alkyl chain amino alcohols from the Mediterranean sponge Clathrina coriacea, J. Org. Chem. 61 (1996) 7415e7419. [3] A. Aiello, E. Fattorusso, A. Giordano, M. Menna, C. Navarrete, E. Munoz, Clavaminols AeF, novel cytotoxic 2-amino-3-alkanols from the ascidian Clavelina phlegraea, Bioorg. Med. Chem. 15 (2007) 2920e2926. [4] A. Aiello, E. Fattorusso, A. Giordano, M. Menna, C. Navarrete, E. Munoz, Clavaminols GeN, six new marine sphingoids from the Mediterranean ascidian Clavelina phlegraea, Tetrahedron 65 (2009) 4384e4388. [5] T. Vijai Kumar Reddy, B.L.A. Prabhavathi Devi, R.B.N. Prasad, M. Poornima, C. Ganesh Kumar, Total synthesis and antifungal activity of (2S,3R)-2aminododecan-3-ol, Bioorg. Med. Chem. Lett. 22 (2012) 4678e4680. [6] (a) S. Jiang, Y.L. Wu, Z.J. Yao, First synthesis of mosquito larvicidal butenolides I and II, Chin. J. Chem. 20 (2002) 692e696; (b) A. Sharma, S. Sankaranarayanan, S. Chattopadhyay, Expedient synthesis of (R)-patulolide A, J. Org. Chem. 61 (1996) 1814e1816; (c) S.F. Lu, Q.Q. O’yang, Z.W. Guo, B. Yu, Y.Z. Hui, Total synthesis of tricolorin A, J. Org. Chem. 62 (1997) 8400e8405; (d) S.F. Lu, Q.Q. O’yang, Z.W. Guo, B. Yu, Y.Z. Hui, The first total synthesis of tricolorin A, Angew. Chem., Int. Ed. Engl. 36 (1997) 2344e2346; (e) J.A. Smith, K.R. Brzezinska, D.J. Valenti, K.B. Wagener, Precisely controlled methyl branching in polyethylene via acyclic diene metathesis (ADMET) polymerization, Macromolecules 33 (2000) 3781e3794.

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