Marine Terpenes and Terpenoids. VI. Isolation of Several Plausible Precursors of Marine Cembranolides, from the Soft Coral, Sinularia mayi

Abstract

Six new cembranoid diterpenes, sinulariols C and D (1 and 2a), sinularial A (3), sinularic acid A (4), and sinularones A and B (5 and 6) were isolated from the lipid extract of the soft coral Sinularia mayi, together with four known compounds. The structures of the new compounds were elucidated by means of spectroscopic analyses, Horeau determination, and chemical conversion. Sinulariol C (1) was found to be an C-14 isomer of “13-hydroxyneocembrene” (8a) and gave sinularone A (5) on oxidation. Sinularial A (3) is the first example of a cembranoid aldehyde isolated from marine sources. Compounds 1 to 4 are plausible precursors to the cembranoid lactones found in various soft corals.