Studies of Australian Soft Corals. XLIV. New Diterpenes From Sinularia polydactyla (Coelenterata, Anthozoa, Octocorallia)

The soft coral Sinularia polydactyla has yielded six highly functionalized diterpenes. The known diterpenes pukalide (2) and 1-epithunbergol (3) were readily identified by spectral comparison with authentic samples. The new natural products 13 α-acetoxy-11β, 12β-epoxypukalide (4),13 α-acetoxypukalide (5) and its allylically rearranged isomer (6) were identified on the basis of 2D-n.m.r. experiments at 300 MHz and by spectral comparison with the known compounds pukalide (21, lophotoxin (8) and epoxypukalide (9). A minor, relatively unstable metabolite (7) is tentatively identified as a 3,4:5,6-bisepoxy derivative of (6). The biological implications of these findings are discussed.