VirenamideD

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. 

During this time, the total synthesis of several marine sulfur-containing natural products cited in this review has been reported and they confirmed the suggested structures. This is the case of the synthesis of some sulfonoceramides (e.g. flavocristamide A (318) discussed in the sulfonic acid and their derivatives section [366], and the synthesis of the thiazole-containing compounds bistratamide D (381) [367], trunkamide (388) [368], mollamide (393) [369], dolastatin I (409) [370], and virenamide B (414) [371]. 

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. 

Figure 8 Structures of compounds 33 (aeruginosamide), 34 (dolabellin) and 35 (virenamide A).

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). 

Feng, Y.J. and Bowden, B.F. (1997) Studies of Australian ascidians. VI. Virenamides D and F, linear peptides from the colonial didemnid ascidian Diplosoma virms. Aust.J. Che-m., 50, 337-339. 

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