Isoprenoids from the Soft Coral Sinularia erecta
J ournal of Natural Products, 1998, Vol. 61, No. 7 875
were measured on a Perkin-Elmer Model 141 polarim-
eter using a 1 cm microcell.
2.08 (1H, bd, J ) 13.9 Hz, H-13b), 2.15 (1H, t, J ) 11.5
Hz, H-1), 2.37 (1H, t, J ) 13.9 Hz, H-13a), 2.58 (1H,
dd, J ) 11.5, 4.3 Hz, H-9a), 2.65 (1H, dd, J ) 14.5, 2.1
Hz, H-2b), 3.40 (1H, dd, J ) 8.9,7.0 Hz, H-2a), 3.82 (3H,
s, OCH3), 4.49 (1H, s, H-7), 4.73 (1H, s, H-16b), 4.76
(1H, s, H-16a), 6.96 (1H, d, J ) 11.4 Hz, H-10), 5.59
(1H, s, H-11), 6.70 (1H, s, H-5); 13C NMR δ 44.1 (d, C-1),
31.7 (t, C-2), 160.5 (s, C-3), 116.8 (s, C-4), 108.8 (d, C-5),
152.5 (s, C-6), 75.6 (d, C-7), 73.6 (s, C-8), 42.7 (t, C-9),
78.6 (d, C-10), 148.0 (d, C-11), 133.6 (s, C-12), 21.6 (t,
C-13), 27.7 (t, C-14), 146.1 (s, C-15), 112.6 (t, C-16), 18.9
(q, C-17), 165.0 (s, C-18), 19.3 (q, C-19), 173.3 (s, C-20),
51.6 (q, OCH3); EIMS m/z 372 [C21H24O6, M+, 5], 340
(10), 223 (100), 168 (80).
Biologica l Ma ter ia l. The soft coral S. erecta was
collected at the lagoon of Mayotte, Comoros Islands,
northwest of Madagascar, by scuba at a depth of 10 m
in May 1995. A voucher specimen is deposited at Tel-
Aviv University (AMS-22).
Extr a ction a n d Isola tion . The soft coral (300 g)
was homogenized and extracted with CHCl3/MeOH (1:
2) to give a brown gum (1 g) after evaporation. The gum
(800 mg) was partitioned into aqueous MeOH and
hexane, CCl4, and CHCl3. The hexane fraction (450 mg)
was subjected to silica gel chromatography to give
germacrene D (12 mg) and germacrene E (1, 9 mg). The
CCl4 fraction (160 mg) gave, upon silica gel chromatog-
raphy, a 3:1 mixture of compounds 2 and 3 (25 mg). The
CHCl3 fraction (150 mg) afforded, upon repeated Sepha-
dex LH-20 chromatography eluted with MeOH/CHCl3
(1:1), mayotolide A (4, 20 mg) and mayotolide B (5, 8
mg).
Ger m a cr en e E (1): oil; [R]D +2.1° (c 0.23, MeOH);
1H and 13C NMR, see Table 1; HREIMS m/z 204.1892
[M+] (calcd for C15H24, 204.1897).
Nor cem br en e (2) a n d ep i-n or cem br en e (3): oil
(3:1 mixture). The 13C NMR (CDCl3) and 1H NMR
(C6D6) of the major compound (2) were identical with
the reported data for norcembrene.5
Com p ou n d 3: oil; 1H NMR (C6D6) δ 0.92 (3H, s, Me-
18), 1.03 (1H, dd, J ) 15.3,3.0 Hz, H-9b), 1.47 (3H, s,
Me-17), 1.52 (1H, m, H-9a), 2.00 (1H, m, H-13b), 2.11
(1H, dd, J ) 14.2, 11.2 Hz, H-4b), 2.29 (1H, d, J ) 14.2
Hz, H-4a), 2.38 (1H, m, H-13a), 4.08 (1H, d, J ) 11.2
Hz, H-5), 4.28 (1H, m, H-10), 4.78 (1H, s, H-16b), 4.81
(1H, s, H-16a), 6.41 (1H, s, H-11); 13C NMR δ 212.0 (s,
C-6), 207.9 (s, C-3), 151.6 (d, C-11), 145.2 (s, C-15), 130.8
(s, C-12), 113.0 (t, C-16), 78.6 (s, C-8), 78.4 (d, C-10),
74.7 (d, C-5), 51.0 (t, C-7), 50.1 (t, C-9), 43.9, 41.6 (t,
C-2,4), 38.7 (d, C-1), 29.1, 17.9 (t, C-13,14), 27.8 (q, CH3-
18), 18.3 (q, CH3-17).
1
Com p ou n d 8: oil; H NMR (CDCl3) δ 1.42 (3H,s),
1.51 (1H, m), 1.71 (3H, s), 1.80 (1H, m), 1.89 (1H, dd, J
) 14.8, 12.0 Hz), 2.08 (1H, bd, J ) 14.5 Hz), 2.15 (1H,
t, J ) 11.0 Hz), 2.30 (1H, t, J ) 14.5, 6.0 Hz), 2.58 (1H,
dd, J ) 14.9, 4.1 Hz), 2.64 (1H, dd, J ) 14.5, 2.0 Hz),
3.46 (1H, dd, J ) 8.9, 7.0 Hz), 3.85 (3H, s, OCH3), 4.56
(1H, s), 4.80 (1H, s), 4.83 (1H, s), 4.94 (1H, bd, J ) 11.7
Hz), 5.66 (1H, s), 6.74 (1H, s); EIMS m/z 372 [C21H24O6,
M+, 10].
1
Com p ou n d 9: oil; [R]D + 24.0° (c 0.25, MeOH); H
NMR (CDCl3) δ 1.04 (3H, s), 1.50 (3H, s), 1.75 (3H, s),
1.76 (3H, s), 3.82 (3H, s), 4.09 (1H, s), 4.80 (1H, s), 4.83
(1H, s), 4.92 (1H, s), 4.94 (1H, d, J ) 4.9 Hz), 5.18 (1H,
s), 5.21 (1H, s), 5.70 (1H, s), 6.34 (1H, s), 6.60 (1H, s),
7.10 (1H, s); EIMS m/z 730 [C41H46O12, M+, 15], 712 (20),
372 (C21H24O6, 65), 340 (55), 208 (60), 153 (100).
Ack n ow led gm en t . Thanks are due to Dr. Y.
Benayahu for the identification of the soft coral.
Refer en ces a n d Notes
(1) Faulkner, D. J . Nat. Prod. Rep. 1997, 14, 259-302 and earlier
reports in this series.
(2) Benayahu, Y.; Loya, Y. Helgolander Wiss. Meeresunters. 1977,
30, 362-382.
(3) Coll, J . C. Chem. Rev. 1992, 92, 613-631.
(4) Kashman, Y.; Loya, Y.; Bodner, M. Groweiss, A.; Benayahu, Y.,
Naveh, N. Mar. Biol. 1980, 55, 255-259.
(5) Fenical, W. In Marine Natural Products: Chemical and Biologi-
cal Perspectives; Scheuer, P. J ., Ed.; Academic Press: New York,
1978; Vol. II, pp 187-200.
Compound 4: oil; [R]D +43.0° (c 0.33, MeOH); IR
(KBr) νmax 3423, 2950, 1742, 1620, 1223, 1066, 1037
cm-1 1H and 13C NMR, see Table 2; correlations
;
(6) Kashman Y.; Bodner, M.; Finer-Moore, J . S.; Clardy, J . Expe-
rientia 1980, 36, 891-892.
observed in a COSY experiment, H-1/2a,2b,14a,14b;
H-5/7; H-10/9a,9b,11; H-13a/13b, 14a,14b; H-1′/2′a,2′b,
14′a,14′b; H-5′/7′; H-10′/9′a,9′b,11′; H-13′a/13′b, 14′a,
14′b; FABMS m/z 739 [C40H44O12Na, M+ + Na].
Com p ou n d 5: oil; [R]D +48.5° (c 0.23, MeOH); IR
(KBr) νmax 3420, 2950, 1742, 1621, 1066, 1040 cm-1; 1H
and 13C NMR, see Table 2; FABMS m/z 739
(7) Tursch, B. Pure Appl. Chem. 1976, 48, 1-6.
(8) Missakian, M. G.; Burreson, B. J .; Scheuer, P. J . Tetrahedron
1975, 31, 2513-2525.
(9) Coll, J . C.; Bowden, B. F.; Heaton, A.; Scheuer, P. J .; Li, M. K.
W.; Clardy, J ., Schulte, G. K.; Finer-Moore, J . J . Chem. Ecol.
1989, 15, 1177-1179.
(10) Bowden, B. F. Coll, J . C.; Wright, A. D. Aust. J . Chem. 1989,
42, 757-763.
(11) Schmitz, F. J .; Vanderah, D. J .; Cierseszko, L. S. Chem.
Commun. 1974, 407-408.
[M+ + Na].
(12) Carmely, S.; Groweiss, A.; Kashman, Y. J . Org. Chem. 1981,
46, 4279-4284.
Ba sic Hyd r olysis of Com p ou n d s 4 a n d 5. May-
otolide A (4, 20 mg) in a mixture of MeOH (1 mL),
acetone (10 mL), and MeI (0.5 mL) in the presence of
anhydrous K2CO3 (10 mg) was left at room temperature
for 20 h. The carbonate was then filtered away, the
solvent evaporated under vacuum, and the residue
subjected to a silica gel column to afford pukalide (6, 3
mg) and compound 7 (4 mg). Hydrolysis of mayotolide
B (5, 8 mg), under the same conditions as described for
4, afforded pukalide (6, 2 mg) and compounds 8 (3 mg)
and 9 (2 mg).
(13) Sato, A.; Fenical, W.; Qi-tai, Z.; Clardy, J . Tetrahedron 1985,
41, 4303-4308.
(14) Beechan, C. M.; Djerassi, C. Tetrahedron 1978, 34, 2503-2508.
(15) Weinheimer, A. J .; Schmitz, F. J ., Ciereszko, L. S. In Drugs from
the Sea. Trans. Mar. Technol. Soc. 1967, 135.
(16) The 3:1 ratio between 2 and 3 is seen already in the NMR
spectrum of the crude extract. Moreover, as TFA does not
equilibrate the isomers and the basic equilibration is very slow,
both epimers are natural products.
(17) Surprisingly, the mixture of compounds 2 and 3 was not stable
on a RP-18 column.
(18) Traces of the methyl ester of 4 were also obtained during the
methylation-methanolysis reaction.
(19) It is important to note that freeze-drying of soft corals should
not be used if the content of sesquiterpenes is of interest, as the
volatile compounds will be lost with the water.
1
Com p ou n d 7: oil; H NMR (CDCl3) δ 1.42 (3H, s,
Me-19), 1.50 (1H, m, H-14b), 1.72 (3H, s, Me-17), 1.80
(1H, m, H-14a), 1.85 (1H, dd, J ) 13.6, 12.0 Hz, H-9b),
NP9705064