Sesquiterpenoids and diterpenoids from Tithonia longiradiata

Phyrochemistry, Vol. 31, No. 12, pp. 4227.4231, 1992 Printed in Great Britain.

SESQ~ITERP~NOIDS

0031 9422/92 $5.00 + 0.00 Q 1992 Pergamon Press Ltd

AND DITERPEN~IDS

FROM T~T~~NIA

LONGIRADIATA ANA LIDIAP~REZ Instituto de Quimica, Universidad

C., OLGALARAM~IW~

ALFONSOROMODEVIVAR

National Autbnoma de Mtxico Circuito Exterior, Ciudad Universitaria, Coyoackn 04510, MCxico, D.F. (Received in revised form 5 May 1992)

Key Word I~ex-~i~~on~~ heliangolides.

~n~i~ad~a~~ Compositae; Heliantheae; sterols; sterol gtucosides; fiavones; diterpenes;

Absttm-Tithonia longiradiata yielded several known compounds and the new heliangolides 3-acetyl-l5-hydroxy2’,3’-dihydroleptocarpin and 15”hydroxy-2’,3’-dihydroleptocarpin. The structures were established by spectroscopic studies, chemical transformations and confirmed by a chemical correlation with dihydrohelianginol of known stereochemistry.

INTRODUCTION

The genus Tithonia comprises 13 taxa [t], five of these have been studied chemically and were shown to contain heliangolides [2, 33, eudesmanolides [3], diterpenes [43 and flavonoids [2,4]. In continuation of our systematic studies of this genus, we now describe the results of a chemical examination of the aerial parts of T. longiradiata collected in the State of Chiapas.

The hexane extract of T. longimdiata gave the fiavone nevadesin (la) [6]. The acetone extract afforded sitosterol, stigmasterol, their glucosides [Sj and the known compounds 2-4,5a and b. We did not find the flavonoids previously reported for this species [ 131; instead we isolated the flavones la and b [7-12-J. The new heliangolides 6b and d were obtained only in admixture with the corresponding known dehydro derivatives 6s and c 1141. As many attempts to resolve these mixtures by column chromatography, TLC on AgNO,-silica gel and HPLC failed, we decided to study the binary mixtures. The heliangolides 6a and b showed hydroxyl, y-lactone and ester groups in the IR spectrum bands (3506, 1762 and 1737 cm- ‘). The mass spectrum showed a peak at m/z 402, assigned to [6b-H,O]+, peaks due to acetyl and a-me~ylbutyryl were also shown. Additional peaks at m/z 83 and 55 indicate the presence of 3-acetyl-14hydroxyleptocarpin #a). The ‘H NMR spectrum showed typical signals of l,lO-epoxyheliangolides (Table 1). The presence of esters at the C-3 and C-8 positions were shown by the low field signals at 65.35 (dd 5=4.5,5.7 Hz) and 5.17 (m). The heliangolide 6b and the known compound 6a contain a y-lactone closed to C-6 (66.07/6.1 dd) and a hydroxyl group at C-15 (two AB systems, 6 4.19). Acetylation of 6a and b resulted in formation of 6e and f, whose ‘H NMR spectrum showed the C-15 methylene at lower field (64.6). The appearance of duplicated signals for H-5, H-6, H-13, H-14 and H-15 as well as the signals for two acetate (62.12 and 2.15), an angelate (S6.8 qq, J

=2.02 and 1.8 Hz) and those of an a-methylbutyrate (60.87 d and 1.13 t) in the ‘HNMR spectrum (Table l), indicated the presence of two substances. The 13C NMR spectrum (Table 2) was in close agreement with the above assumption. Mild alkaline hydrolysis saponified only the C-3 acetates, thus giving 6c and d whose ‘H NMR spectra show the typical signals of heliangolides containing a /? hydroxyl group at C-3. Therefore, compounds 6a and 4 are 3a~tylheliangol~d~ esterified at C-8 with different acids. The stereochemistry at C-8 was established in the following manner: 6a and b were hydrogenated with Pd-C in acetic acid to give a mixture of four substances. The more polar fraction was a mixture of the 1i,13-dihydroderivatives 7a and b. In 7a the angelate was isomerized to a tiglate (Table 1). This mixture was saponified with &CO,, affording the deacetyl compounds 7e and f, thus confirming that the only difference between 6a and b is the ester group attached at C-8. The less polar mixture was composed of 7a and b which are the 15-deoxy derivatives of 7e and d, as shown by the ‘H NMR signal of the new vinylic methyl group (61.48/1.45, Table 1). When this mixture was saponified as described for 7a and b, it afforded dihydrohelianginol [ 151. Therefore, the side chain at C-8 is p oriented and 6a corresponds to 3-acetyl15-hydroxyleptocarpin, a compound previously isolated from T. rotundifofoliu [14] and 6b is the new heliangolide 3a~tyl-lS-hydroxy-~,~-dihydrolept~arpin. The naturally occurring 6c and d had spectroscopic data identical with those of the partial saponification products of 6a and b. Acetylation of 6e and d yielded the same diacetates previously obtained from 6a and b in addition to the monoacetates 6g and h. The latter substances retained a non-acetylated C-3 hydroxyl group probably due to steric hindrance [16]. Therefore, 6c is isolated from 15_hydroxyleptocarpin, previously T. rotundi$olia [14] and 6d is the new compound 15hydroxy-~,~~hydrol~tocarpin. The results described here are in agreement with the close taxonomic relationship of Tithonia, Welianthus and

4227

A. L. PEREZC. et al.

4228

20 R=H 2b R=OH

hi R=H lb R=OMe

OH

$a R-Ang 5b R=a-Mebut

RIO

RIO

6a 6b 4e &I 6

RI=Ac R2=H Rt=Ac R2=H R1=R2=H R1=RZ=H Rl=R2=Ac

4f BI=R2=Ac

@I RI=H RpAc 6b RpH

RpAc

R3=Ang R3=a-Mebut R3=Ang Rs=a-Mebut R3=Ang R3=a-Mebut R3=Ang Rs=a-Mebut

Viguiera [I] since the three genera elaborate similar secondary metabolites [ 17, IS].

7~ Rt=Ac Rz=OH R3=Tigl 7b Rt=Ac Rz=OH Rs=a-Mebut 7c Rt=Ac R2=H R3=Tigi 7& Rt=Ac Rz=H Rs=u-Mebut 7e R1=H Ra=OH Rs=Tigi 7f Rt=H R;?=OH Rs=a-Mebut 7II R1=H R2=H R3=H

the same or

EXPERIMENTAL Extraction and separation. Dried and ground aerial parts of ZTrkoniu longirudiata (Bertot.) S. F. Blake (831 g) collected in Chiapas, Mexico, 1989 (Voucher MEXU 499232, deposited in the Herbario of the Instituto de Biologia U.N.A.M.) were extracted with hexane and Me&O. The hexanic extract (25.06 g) was chromatographed over silica gel using hexane and mixtures of hexane-EtOAc. The hexane-EtOAc (17:3) frs were rechromatographed using hexane EtOAc (9: 1) yielding 22.4 mg of nevadensin (la) [6]. The Me,CO extract (34 g) after successive chromatography over silica gel, afforded 74 mg of la, 78.4 mg of hymenoxin (lb) [?j, 66.3 mg of ent-kauren-19”oic acid (2a) [S],

19.2 mg of a mixture of sitosterol and stigmasterol, 149 mg of mixed grandifloric acid (Zb) and 17-hydroxy-e~f~kaur-f5~n-l9oic acid (3) [9], Ii mg of enr-l5~,16~-epoxy-l7-hydroxykaur~19-oic acid (4) [lo], 951.3 mg of a mixture of budlein A (Sn) [ll] and ~7,18-dihydrobudIein A (5h) [12], 121 mg of mixed sitosterol and stigmasterol glucosides [S], 898.7 mg of a mixture of 3acetyl-lS-hydroxyleptoca~in (6a) [14] and 3-acetyl-15hydroxy-2’,3’-dihydroleptocarpin (6b) and 57.8 mg of 1S-hydrox15-hydroxy-2’,3’yleptocarpin (6e) [14] mixed with dihydroleptocarpin (&I). Compounds la, 2a, sitosterol and stigmasterol were identified by comparison with authentic samples. Compounds lb, 2b, 3,4, 51, b and the glucosides of sitosterol and stigmasterol were identified by comparison of mps and spectroscopic data with those reported in the literature. Compounds 6a and b. Crystals from hexane-EtOAc, mp 238-240”, [z], - 111’(CHCI,; c 0.2), UV igzFH nm (log8) 201

4229

Terpenoids from TEthonialongiradiata Table 1, ‘HNMR

spectral data of ~rn~un~

6a-b and 7a-f

H

6a, b*

6e,d

6e,f

6&h

70,b

lc, d

7e, f

1

2.9 m

28m

2.8 m

2.75 m

2.8 m

2.8 m

5.54 br d (10.5)

5.16 dd (3. 5) 5.42 dd

4.5 m

(2*4) 5.67 br d

(11)

(1.5, 11)

(11)

6.0 br d (11) 6.03 br d (11) 2.95 m

6.02 br d

2.8 m

6.07 dd (2, 10.5) 6.1 dd (2, 10.5) 2.8 m

6.5 br d (11) 6.52 br d (11)

5.15 m

5.16 m

5.1 m

9b

2.95 dd (4.5,9.5) 2.6 dr (4.5,15.7) 1.8 ddd (2.2,9.5, 15.7) 5.35 dd (2.Z4.5) 5.54 d (11.3) 5.5 d (11.3) 6.07 dd (2.2, 11.3) 6.1 dd (2.2, 11.3) 2.97 dt (6.7,2.2) 5.17 m 2.72 dd (4.5, 14) 1.37 dd

13a

(514) 6.39 d

6.35 d

6.36 d

6.36 d

(2.2)

(2)

(2)

(2)

2a 2b 3 5

6

7 8 9a

13b

14 15 a-Mebut 2

5.82 d

2.5 m

4.58 dd

5.3 dd

(2 4) 5.54 dd (2.1, 11)

(3.5) 5.47 br d

6.6 dd (2.5, 11) 6.65 dd (2.5, 11)

29m 5.1Sm

5.75 d

(2.2)

5.83 d

(1.5) 5.77 d

(2.2)

fW

(16)

(1.5)

1.52 s l.S4S 4.19 2fAB)

1.5 s 1.43 s 4.08

(11) 6.05 br d

(111

6.07 br d

(11)

5.75 br s

4.55 m

5.75 d

5.3 dd

(11)

6.06 br d

(11) 28m 5.1 m

5.73 br d

28m

5.1 m

1.1 d

1.15 d

1.15 d

(7)

(7)

(7)

1.5 s 1.45 s 4.2 br s

1.4s s 1.48 s 1.91 d

1.45 s 1.5 s 4.1 s

(1.5) 5.77 d

0.S)

1.5 s

1.5s 1.51 s 4.5 d

4.6 s

0.5)

(1.5)

238 sext

(6.8)

3a

1.64 hept

(6.8) 1.5 kept

3b

WI

4 5 Ang 3

t 65.8)

0.88

0.9 t

0.9

1.13 d

(7) 1.12 d

(7.5) 1.12 d

(7)

(7.5) 1.15 d

(7.5) l.lOd

(7.5) 1.13 d

(6.8)

(7)

(7.5)

(7)

6.8 94

$.09&rq (7) 1.98 dq

6.1 m

6.07 br q

(7.5) Tigl. 6.86 br q

(7.5) Tigl. 6.87 br q

(7.5) Tigl. 6.85 br q

2.05 m

(7) 1.97 dq

(7) 1.8 br d

(7) 1.8 br d

(7)

1.86 br s

(7, 1.5) 1.81 q

(7)

(7) 1.83 br s

(7)

(1.5, 6.7) 2.02 dq (6.7, 1.5) 1.88 q

4 5 AC

0.9

0.87

WI

2.12s 2.15 s

t

(7, 1.5) 1.87 q

0.85

t

0.82

t

1.12 d

1.85 br s

t

t

1.81 br d 1.85 br s

(1.5) 2.1 s 2.149

Run at 80 MHz, CD&, TMS as int. standard, Values are in ppm, Values in parentheses are coupling constants in Hz *Run at 300 MHz. A~ignm~ts are based in the COSY spectrum.

(4.42), 208 (4.37). IR vZ:‘~ cm- + 3%X$1762,1737,1663. EIMS 70 eV, m/z (ret. int.): 402 EM-H,O]+ (0.3), 337 [M -RCO]+ @cl), 321 [M-RCOJ+ (0.3), 260 [M-RCO,H-HOAc]+ (4), 247 [321-CZH30-MeO]+ (12), 85 [CSH90]+ (24), 83

[CsH,O]+ (100x 57 [C&H,]+ (93.7), SS [C,H,]+ (77.1), 43 [C2H,0]+ (96.8). Compounds 6c and d. Pale yellow oil, [aID -84.5” (CHCI,; c 0.2). UV J.g:y nm (logs): 205 (4.40). IR vEFla cm-‘: 3473,1762,

A. L. PEREZ C. er al.

4230

Table 2. 13C’NMR spectral data of compounds 6a and b C 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15

60.1 31.5 74.2 141.2 125.8 75.5 47.9 70.2 43.6 58.4 136.6 129.8 125.6 19.1 65.1

60.1 31.5 14. I 141.1 75.4 47.8 43.3 58.3

a-McBut

1 2 3 4 5

166.0 41.2 26.4 11.3 16

Ang 1 2 3 4 5

166.0 126.2 141.6 15.8 19.5

AC 1 2

169.8 21.0

20.2

Run at 75 MHz, CDCI,, TMS as internal standard. Assignments were done using the APT technique.

gel using hexane--,EtOAc (3 : 7) yielded 42.2 mg of a mixture of 7a and b and 101.9 mg of an unseparable mixture of 7c and d. Compounds 7a and b. Crystals from hexane-EtOAc, mp 184. 186”. IR ~$!$‘~crn-‘: 3513, 1770, 1736,1648. EIMS 70eV, m/z (rel. int.): 422 [M, CZ2H,aOs]+ (O-S),404 [422-H,O]+ (0.2), 364 [CZ2H,,0, - HOAc] * (0.3), 362 [422 - HOAc] + (0.2), 262 [M-RCO,-HOAc]+ (IO), 85(CsH,O]+ (52.2), 83 [C,H,O]+ (lOO), 57 [C4H9]+ (85), 55 [C,H,]+ (52), 43 [CzH30]+ (71.5). Compounds 7c and d. Crystals from hexane-EtOAc, mp 195-197”. IR v~~~t3cm-‘: 1766, 1738. EIMS 70 eV, m/z (rel. int.): 408 CM, CJJ&J+ (0.3), 406CM, C,,H,,O,I+ (21,348 [408 - HOAc] + (1.2), 346 [406- HOAc]+ (I), 263 [M - RCO,H -C,H,O]+ (72.5), 8.5 [C,H,O]’ (38), 83 [CsH,O]+ (71.5). 57 [C,H,] * (48.9), 55 [C,H,] + (35), 43 [C,H,O] + (100). Saponijcation of 7a and b. Compounds 7s and b (48 mg), 50 mg of K,CO, in MeOH (2 ml) were stirred at room temp. for 1 hr. The solvent was ehminated by an air stream and the residue dissolved in EtOAc, washed with H,O, dried with Na,SO, and coned. The residue was chromatographed and eluted with CHCI,-Me&O (3 : 2) yielding 22.4 mg of 7e and f as an oil. IR Y:::“ cm-‘: 3519, 1766, 1731, 1648. EIMS 70eV. m/z (rel. int.): 280[M-RCO,H]’ (0.4),85(C,H,O]” (13), 83 [C~H,Oli(~), 57 [C&H,] + (100), 55 [C,H,] + (84.1), 43 (89.7). Saponification of 7c and d. A soht of 7c and d (20 mg) and of K&O, (40 mg) in MeOH (1 ml) were stirred at room temp. for 12 hr and worked-up as described above. Chromatography of the residue using hexane-EtOAc (7: 13) afforded 2 mg of li,13dihydrohelianginol(7g) [15] mp 202-204” from hexane-EtOAc, identified by direct comparison with an authentic sample. Acetylation of 6c and d. Compounds 6e and d (30 mg) were acetylated in the usual manner. The residue was purified by chromato~aphy. The hexane-EtOAc (9 : 11) eluates yielded I.5 mg of 6e, f and 17 mg of 6g, h as an oil. IR vale” cm-i: 3599, 1761,1739,1661. EIMS 70eV,m/z(reL int.): 402 [M-H,01 (0.9) 337 [M - RCO] + (2.5), 243 [M - RCO,H - HO&c- HO] + (S), 85 [C,H,O] + (27), 83 [C:C,H,O]+ (52.2), 57 [C.&]+ (59.5). 55 [C,H,] + (55.1), 43 [C,H,O] + (100). Acknowledgements-We are indebted to chemists Ma. de1 Rocio Patina, Luis Velasco and Rut&t Gavifio for technical assistance. Thanks are also due to Mr. Francisco Ramos (Instituto de Biologia, U.N.A.M.) for identification of the plant.

1735, 1661. EIMS 70eV, m/z (rel. int.): 378 [M, C,,H,,O,]* (O.l), 362 [CzoH2s07-H20]+ (O.l), 360 [378-H,O]’ (O.I), 260 [M-RCOzH-HzO]+ (O.l), 85 (C,H,O]’ {18), 83 [C,H,O]+ (45.8). 57 [C,H,]+ (73). 55 [C,H,]+ (96.Q 43

REFERENCES La Duke, J. C. (1982) ~hodoru 84,453. Baruah, N. C., Sharma, R. P., Madhusudanan, K. P., Thyagarajan, G., Herz, W. and Murari, R. (1979).5. Org. Chem. 44, 1831. Alonso-Lopez, M., Barges-dei~astilio, J., Rod~gu~-Ubi~ J. C. and Vizquez-Bueno, P. (1986) J. Chem. Sot., Perkin

CW+,Ol UW. Acetylation of 6a and b. Compounds 6a and b (100 g) were acetylated in the usual manner. Chromatography of the reaction mixt. with hexane-EtOAc (11: 9) afforded 60.6 mg of the mixture &, f as an oil. IR ;izz’-l cm- r: 1761,1740,1663. EIMS70eV,m/z (rel. int.): 464 [M, C,,H,,O,] i (0.2), 404 [464 - HOAc] + (0.6), 402 [CZaH3a0, -HOAc]+ (2) 379 [M - RCO] + (2.7), 302 [M -RCO,H-HOAC)~ (S), 242 [302-HOAcJ+ (7.5), 85 [CsH,O]+ (lo), 83 [C,H,O] (22.5), 57 (&Ha]+ (X3), 55 CC,H,]+ (31), 43 [C,H,O]+ (100). Saponificntion of6a and b. A suspension of6a and b(lO0 mg) in 2 ml of 0.62 M KOH was stirred at room temp. for 2 hr 40 min, then the reaction mixt. was neutralized with H,SO, soln and NaCl added. The reaction mixt. was extracted with EtOAc, dried and evapd. Chromatography of the residue over silica gel using hexane-EtOAc (7: 3) yielded 4.9 mg of 6c, d as on oil. Hydrogen&on of68 and b. The mixed heliangolides 6a and b (150 mg) in HOAc (20 ml) were hydrogenated over 20 mg of 5% W-C at atm. pres. for 4.5 hr. The reaction mixt. was worked-up in the usual manner. Chromatography of the residue over silica

Trans. I 2017.

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Misra, A. N. and Tiwasari, H. P. (1973) Phyt~he~stry

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3254. 8. Henrick, C. A. and Jefferies, P. R. (1964) Aust. J. Chem. 17, 915. 9. Yahara, S., Ishida, M., Yamasaki, K., Tanaka, 0. and Mihashi, S. (1974) Chem. Pharm. Bull. 22, 1629. 10. Herz, W., Kulanthaivel, P. and Watanabe, K. (1983) Phytochemistry 22, 202 1.

Terpenoids

from Tithonia

11. Romo de Vivar, A., Guerrero, C., Diaz, E., Bratoeff, E. and JimCnez, L. (1976) Phytochemistry 15, 525. 12. Delgado, G., Romo de Vivar, A. and Herz, W. (1982) Phytochemistry 21, 1305. 13. La Duke, J. C. (1982) Am. J. Bot. 69, 784. 14. PBrez, C. A. L., Colin, V. M. C., Guerrero, R. C., Cruz, R. M. L. and Romo de Vivar, R. A. (1984) Phytochemistry 23,823. 15. Morimoto, H., Sanno, Y. and Oshio, H. (1966) Tetrahedron 22, 3173.

longiradiata

4231

16. Holub, M. and Samek, Z. (1977) Collec. Czech. Chem. Commun. 42, 1053. 17. Romo de Vivar, A. and Delgado, G. (1985) BoI. Sot. Chil. Quim. 30, 79. 18. Gershenzon, J., Ohno, N. and Mabry, T. J. (1981) Rev. Latinoam. Quim. 12, 53.