Novel verrucosins from the skin of the Mediterranean nudibranch Doris verrucosa

Nine new diterpenoid acid glycerides (4-12) have been isolated, together with the previously reported 13 and 14, from the skin extract of the Mediterranean nudibranch Doris verrucosa. The structure and the relative stereochemistry of the new metabolites were established by interpretation of spectral data. Absolute stereochemistry of the diterpenoid part was suggested by biogenetic considerations as well as by comparison of CD profiles of 4-12 with those of verrucosin-A (2) and -B (3), previously isolated from the same mollusc. The S absolute configuration of C-2' of the glyceryl moiety was determined by chemical methods for verrucosin-3 (6), as already reported for 2 and 3, and suggested to be the same for all other verrucosins. (C) 1997, Elsevier Science Ltd.