Cyclic Depsipeptides, Callipeltins

Marine sponges are considered as an untapped reservoir of biologically active natural compounds exhibiting numerous interesting and potentially useful pharmacological activities, including antimicrobial, antifungal, cytotoxic, anti-inflammatory, and immunostimulatory activities. One class of such compounds is the cyclic depsipeptides, which are characterized by the incorporation of at least one ester linkage into their structures. Callipeltin A and its 14 analogs, neamphamide A, papuamides A and B, pipecolidepsin A and 10 homophymines are cyclic depsipeptides isolated from marine sponges, have structurally unique features incorporating several modified amino acid residues, and are well known for their potent HIV-inhibitory activity. A variety of synthetic studies have been undertaken, to elucidate the motifs essential for biological activity and meet the challenge posted by their synthesis. In this chapter, recent progress in the isolation and synthesis of the callipeltins will be reviewed.