58 zyxwvutsrqp J. zyxwvutsrq Org. zyxwvutsr Chem. zyxwvutsrqponmlkjihgfedcbaZYXWVUTSRQPONMLKJIHGFEDCBA A zyxwvutsrqponm part of this crude extract zyxwvutsr (6.51 g) was partitioned between dichloromethane and water. The dichloromethane layer, upon concentration, gave 1.52 g of material, which was then partitioned between hexane and 10% aqueous methanol. The hexane layer was concentrated to give 1.33 g of material which was subjected to flash chromatography, HPLC on silica gel, and reverse-phase HPLC in nearly the same manner as described above to give more naurol A and B. From the combined separations 505 mg of naurol A (l), 61.4 mg of naurol B (2), and 10.1 mg of 3 were obtained. Naurol A (1): white solid; mp 97 OC; [a] zyxwvutsrq = +6.21° (c = 2.64, MeOH); UV X , , , 286 nm (e , 49 131); IR (thin film) 3416 cm-'; IH NMR, see Table I; NMR, see Table I; LRMS (12 eV) m/z (relative intensity) 314.1 (10.3), 278.0 (26.11, 228.0 (10.2), 214.0 (25.5), 192.1 (18.2), 180.0(45.8), 177.8 (lOO.O), 164.0 (16.71, 84.8 (91.6), 82.9 (98.9); FAB MS with added Na+ (m + Na)+ 421; FAB MS (m + H)+ 399; FAB MS with added Li+ (m + Li)+ 405. Naurol B (2): white solid; [a] = +12.63' (c = 0.19, MeOH); UV A , , 292.4 nm (emax 44 236); IR (neat) 3466 cm-'; 'H NMR see Table I; NMR, see Table I; LRMS (12 eV) m/v (relative intensity) 314.1 (5.8), 278.0(10.3), 228.0 (7.9), 213.9 (12.0), 192.0 1991,56,58-62 (11.9), 180.0 (38.5), 177.9 (100.0),164.0 (12.6), 85.0 (46.3), 83.0 (56.9). Compound 3: white film; 'H NMR, see Table I; 13C NMR, see Table I; LRMS (70 eV) m/z (relative intensity) 389.1 (11.3), 387.1 (23.4), 385.1 (17.3), 314.0 (12.0),214.0 (16.9),179.9 (38.1), 177.9 (100.0). Acknowledgment. This work was supported by De- partment of Commerce, NOAA Sea Grant Project NA86AA-D-SG074. We thank Mr. Charles Arneson for specimen collection and Dr. Pat Bergquist, University of Auckland, New Zealand, for sponge identification. We gratefully acknowledge NSF Grant CHE 8113507 and the University of Oklahoma Research Fund for funds to purchase a high-field NMR spectrometer. Registry No. 1, 130246-98-9; 2, 130322-42-8. Supplementary Material Available: 'H and 13C NMR spectra of naurol A and B (4 pages). Ordering information is given on any current masthead page. Sterols of Marine Invertebrates. 63.' Isolation and Structure Elucidation of Sutinasterol, the Major Sterol of the Marine Sponge Xestospongia sp. Russell G. Kerr,t Sutinah L. Kerr,? George R. Pettit,* Delbert L. Herald,* Thomas L. Groy,* and Carl Djerassi*ps Hopkins Marine Station, Stanford University, Pacific Grove, California 93950, Cancer Research Institute and Department of Chemistry, Arizona State University, Tempe, Arizona 85287, and Department of Chemistry, Stanford University, Stanford, California 94305 Received April 5, 1990 A new sterol, sutinasterol ((24R)-24-ethyl-26,26-dimethyl-3~-hydroxycholesta-7,25(27)-diene) with a side chain arising from quadruple biomethylation has been isolated from the marine sponge Xestospongia sp. Since it represents the bulk (94%) of the sterol fraction, it presumably plays a biological role in membrane function. Four minor sterols were also characterized, one of which appears to be a biosynthetic intermediate of sutinasterol. A second trace sterol contains a side chain that is the result of five biomethylations and is the largest sterol isolated from natural sources to date. The structures of these sterols were deduced from spectral data ('H and 13C NMR and MS). A crystal structure study of sutinasterol was performed to determine the stereochemistry of the C24 ethyl group. Introduction The occurrence of a wide variety of novel sterols in sponges has been well documented.2 This includes un- conventional sterol nuclei as well as sterol side chains with cyclopropanes, cyclopropenes, and ones with high degrees of alkylation. Recently, the main emphasis in our labo- ratory has been on elucidating the biosynthesis of these compound^.^ It is most interesting to examine unusual sterols that are present in large quantities, as these very likely play a functional (rather than metabolic) role in cell membra ne^.^ Unconventional sterols often co-occur with conventional ones and are sometimes present in small amountsa2It is therefore particularly interesting when a sponge is found with an unusual sterol as the overwhelm- ingly predominant one. Analysis of a demosponge, Xestospongia sp., from Puerto Rico showed that one sterol, designated sutinast- erol, composed 94% of the sterol mixture. Sutinasterol has not previously been isolated and was shown by MS analysis to have a CI2 side chain, presumably the product ' Hopkins Marine Station, Stanford University. zyxwvutsr t Arizona State University. 8 Department of Chemistry, Stanford University. of quadruple bioalkylation. This information, coupled with 'H and 13C NMR analysis, suggested that sutinasterol had the structure shown in Figure 1. An X-ray crystal structure study was performed to confirm this structure (1) For part 62 in this series, see: Tam Ha, T. B.; Djerassi, C. Steroids 1989, 53, 356. (2) For reviews, see: (a) Djerassi, C. Pure Appl. Chem. 1981,53,873. (b) Ikekawa, I. Sterols and Bile Acids; Danielson, H., Sjovall, J., Eds.; Elsevier: Amsterdam, 1985; Chapter 8. (c) Withers, N. Marine Natural Products; Scheuer, P. J., Ed.; Academic Press: New York, 1983; Vol. 5, p 87. (d) Djerassi, C. Alfred Benzon Symposium 20 Natural Products and Drug Deuelopment; Krogsgaard-Larsen, P., Bragger Christensen, S., Kofod, H., Eds.; Munksgaard: Copenhagen, 1984; p 164. (e) Reference 1 and earlier papers in this series. (3) Inter alia: (a) John, V.; Stoilov, I. L.; Djerassi, C.; Karuso, P.; Poiner, A.; Scheuer, P. J. J. Org. Chem. 1989,54, 1642. (b) Kerr, R. G.; Stoilov, I. L.; Thompson, J. E.; Djerassi, C. Tetrahedron 1989,45,1893. (c) Cho, J.-H.;Thompson, J. E.; Stoilov, I. L.; Djerassi, C. J. Og. Chem. 1988,53,3466. (d) Stoilov, I. L.; Back, T. G.; Thompson, J. E.; Djerassi, C. Tetrahedron 1986,42,4156. (e) Doss, G. A.; Margot, C.; Sodano, G.; Djerassi, C. Tetrahedron Lett. 1988,29,6051. zyxw (0 Doss, C. A.; Silva, C. J.; Djerassi, C. Tetrahedron 1989,45,1273. (g) Stoilov, I. L.; Thompson, J. E.; Cho, J.-H.; Djerassi, C. J. Am. Chem. SOC. 1986, 208, 8235. (4) (a) Carlson, R. M. K.; Tarchini, C.; Djerassi, C. (IUPAC)Frontiers of Bioorganic Chemistry and Molecular Biology; Ananchenko, S. N., Ed.; Permagon Press: Oxford, 1980; p 211. (b) Bloch, K. E. Crit. Rev. Bio- chem. 1983, 14, 47. (c) Lawson, M. P.; Stoilov, I. L.; Thompson, d. E.; Djerassi, C. Lipids 1988, 23, 750. (d) Zimmerman, M. P.; Hoberg, M.; Ayanoglu, E.; Djerassi, C. Lipids. In press. 0022-3263/91/1956-0058$02.50/0 Q 1991 American Chemical Society