I. AN INVESTIGATION INTO THE NATURAL PRODUCTS CHEMISTRY OF THE SOFT CORAL ASTEROSPICULARIA RANDALLI. II. AN INVESTIGATION INTO THE NATURAL PRODUCTS CHEMISTRY OF THE NUDIBRANCH TRIDACHIA CRISPATA. III. STRUCTURE DETERMINATION OF THE 11BETA, 12BETA-EPOXYPUKALIDE FROM THE GORGONIAN LEPTOGORGIA SETACEA.

Abstract

Chapter 1 deals with the twenty-eight compounds which have been isolated from the soft coral Asterospicularia randalli, collected in May 1979 and April 1983 at Guam Island in the Pacific. Seven of the twenty-eight natural products have been isolated earlier from other sources: 13-epi-9-O-de-acetylxenicin (3), xenialactol (8), xeniolide-A (7), xeniolid-B (13), xeniolide-B 9-acetate (14), and 7,8-dihydro-7(alpha), 8(alpha)-epoxyxeniolide-B (15) from the soft corals Xenia macrospiculata and Xenia obscuronata; and peridinin, (71), which has been isolated from various marine and fresh-water dioflagellates. One of the twenty-one new compounds described is the novel steriod 72. The remaining 20 new compounds are: 13-epi-9-O-deacetyl-7,8-dihydro-7(alpha), 8(alpha)-epoxyxenicin (40), isoxenialactol (42), xenialactol 9-acetate (43), 7,8-dihydro-7(alpha), 8(alpha)-epoxyxenialactol (44), {compounds 47, 48, 49, and 50 are the 9-deoxy, 9-deoxy-7,8-dihydro-7(alpha), 8(alpha)-epoxy, 15-dehydroxy-15-acetyldioxy, and 7,8-dihydro-7(alpha), 8(alpha)-epoxy analogs of xeniolide-A (7), respectively}, 18-hydroxyasteroxeniolide-A 9-acetate (52), asteroxeniolide-A (54), asteroxeniolide-A 9-acetate (55), asterospicin (56), 14,15-epoxyasterospicin (58), 14,15-bisepiepoxyasterospicin (59), {compounds 60 and 61 appear to arise from ring opening of the 14,15-epoxides 58 and 59, respectively and are epimeric at C-14}, 3(alpha)-hydroxy-7,8-deepoxy-7,8-dehydroasterospicin (62), asterospiculin (65), 7,8-dihydro-7(alpha), 8(alpha)-epoxyasterospiculin (66), and 4(xi), 12(xi):7(alpha), 8(alpha)-diepoxy-4,12:7,8-tetrahydro-3-O-deacetylasterospiculin (69). The structures of these new compounds were elucidated from spectral data and chemical conversions. The ('13)C NMR spectra are fully assigned.

Chapter 3 deals with the structure determination of 11(beta), (beta)12-epoxypukalide obtained from the sea whip coral, Leptogorgia setacea, collected from Mustang Is, on the Gulf of Mexico. The structure was completely elucidated by spectral analyses.

The purpose of this thesis was to study the natural products chemistry of the soft coral, Asterospicularia randalli (Chapter 1) and the nudibranch, Tridachia crispata (Chapter 2). The structure determination of 11(beta), (beta)12-epoxy-pukalide from the Gorgonian Leptogorgia setacea is also described (Chapter 3).

Chapter two describes the isolation and structure determination of the metabolites obtained from the nudibranch, Tridachia crispata. Eleven metabolites have been isolated from Tridachia crispata, collected from Discovery Bay, Jamaica, in June 1979. Two of these, crispatone (3) and crispatene (4), have been reported earlier from Tridachia crispata, collected from the Caribbean. The remaining nine compounds are new: tridachia-pyrone-E (7), tridachiapyrone-F (8), tridachiapyrone-A (9), isotridachiapyrone-A (10), tridachiapyrone-C (11), tridachia-pyrone-D (12), and tridachiapyrone-G (13). The structures of these compounds were elucidated by spectral analyses and by comparison of the spectral data for tridachione (1), 9,10-deoxytridachione (2), crispatone (3), and crispatene (4).