Virenamide from Diplosoma virens

The virenamides A-C (180-182), thiazole-containing cytotoxic linear peptides, were isolated from the colonial ascidian Diplosoma virens collected on the Great Barrier Reef, Australia. Their structures were... 

Thiazole-containing linear peptides have also been isolated from tunicates. Virenamides A-E (412-416) were obtained from the didemnid tunicate Diplosoma virens, which contains symbiotic prokaryotic algae in its cloacal cavity. The structures of virenamides A-C were determined by HPLC analysis using Marfey s procedure [323] while the absolute stereochemistry of virenamide E (416) was proven by its synthesis from virenamide A (412) [324], Compounds 412-416 showed modest cytotoxicity toward a panel of cultured cells and 412 also exhibited topoisomerase II inhibitory activity. 

Carroll, A. R., Feng, Y., Bowden, B. F., and Coll, J. C., Studies of Australian ascidians. 5. Virenamides A-C, new cytotoxic linear peptides from the colonial didemnid ascidian Diplosoma virens, J. Org. Chem., 61, 4059, 1996. 

The Other modified linear peptides reported are virenamides A-E (43-47) from the didemnid ascidian Diplosoma virens [40,41]. Strictly speaking, these metabolites are apparently derived from 4 amino acids so should be regarded as tetrapeptides, but are more conveniently regarded as carboxy-protected tripeptides (where the carboxyl group has been... 

Another species of Didemnidae from the Great Barrier Reef Diplosoma virens, contains prenylated peptides with a thiazole nucleus, which is particularly common in cydic peptides and depsipeptides. Virenamides A-E are only weakly cytotoxic in vitro (Carroll et al, 1996a Feng and Bowden, 1997) and, like caledonin, these peptides may act as natural antifouling agents (Davis and Bremner, 1999). 

---