Chemical investigation of the extract of the hybrid soft coral Sinularia maxima x Sinularia polydactyla afforded eight terpenoid compounds (1--8). Compounds 1--4 are new cembranoid diterpenes while compound 8, which we named polymaxenolide, represents a novel metabolite with a biosynthetically mixed skeleton linking a cembrane-type diterpene and an africanane-type sesquiterpene. A possible biogenesis is proposed for compound 8. The structures and configurations of the new compounds were determined using spectroscopic methods and X-ray diffraction analysis. The absolute configuration of compound 5 known as 5-epi-sinuleptolide was determined by the Mosher's method and X-ray diffraction analysis. Metabolites 1--3 and 5 exhibited cytotoxic activity while metabolite 6 and 7 exhibited antituberculosis activity. This study shows the importance of hybridization in the marine environment as a source of biological and chemical novelty.*; Compound 5 known as 5-epi-sinuleptolide was subjected to microbial transformation studies to generate analogues that yields structure-activity relationship and to prepare derivatives that are difficult to perform by conventional chemical methods. Three new analogues (9--11) were obtained by fermentation of 5-epi-sinuleptolide with the actinomycete Streptomyces lavendulae. Metabolite 9 was obtained by a stereoselective reduction of a ketone and was further metabolized to compound 10 via a hemiketal reaction. Compound 10 undergoes a reversible reaction to yield compound 11.*; *Please refer to dissertation for diagrams.
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