Studies of Australian Ascidians. IV. Mollamide, a Cytotoxic Cyclic Heptapeptide From the Compound Ascidian Didemnum molle

Abstract

A new cytotoxic cyclic heptapeptide, mollamide, has been isolated from the compound ascidian Didemnum molle. The structure of mollamide was initially deduced from one-dimensional and two-dimensional n.m.r . experiments at 300 MHz. The structure was confirmed by an X-ray crystallographic study, which showed the relative stereochemistry of the cyclic peptide. Hydrolysis of mollamide , and characterization of the amino acids by derivatization with Nα -(5-fluoro-2,4-dinitrophenyl)-L- alaninamide (FDAA; Marfey's reagent) gave the absolute stereochemistry; all constituent amino acids were the L-isomers. Cytotoxicity data are reported.