STUDIES OF AUSTRALIAN ASCIDIANS .6. VIRENAMIDE-D AND VIRENAMIDE-E, LINEAR PEPTIDES FROM THE COLONIAL DIDEMNID ASCIDIAN DIPLOSOMA VIRENS

Two new linear cytotoxic tripeptides, virenamides D and E, have been i solated as minor constituents of extracts of the didemnid ascidian Dip losoma virens collected on the Great Barrier Reef, Australia. Their st ructures were deduced from one-dimensional and two-dimensional n.m.r, spectroscopic data, and the absolute stereochemistry of virenamide E i s proven by synthesis from virenamide A.