SPPS depsipeptides

Studies to elucidate the mode of bacteriostatic property of xanthostatin (XS), a novel depsipeptide antibiotic with an A/-acetylglydne side chain and selective antimicrobial activity against Xanthomonas spp., were carried ont by Kim and coworkers [80]. Two biotransformed XSs were isolated by the treatment of XS with the cell... 

The acid chloride method has been successfully used for the synthesis of depsipeptides by O-acylation of hydroxy acids. Although Fmoc amino acid chlorides were recommended for such reactions, and can be used for the introduction of the first amino acid onto hydroxy resins for SPPS, oxazol-5(4//)-one formation promoted by the presence of the required tertiary amine leads to relatively low yields compared to other activation methods such as those involving UNCA groups. ... 

Depsipeptide SPPS methodology, a method for SPPS applicable to difficult sequences arising from aggregation phenomena. It relies on the synthesis of Ser or Thr isopeptide intermediates with a final 0-N acyl migration step. The principle is identical to the O-acyl isopeptide method, also termed click peptide or switch peptide method that were developed independently by different groups. It was, for example, successfully employed to synthesize the extremely difficult WWDomain FBP28 [I. Coin et al.,/. Org. Chem. 2006, 71, 6171]. 

Cyanobacteria are also sources of substances of pharmaceutical interest, for example, antibiotics [54]. Moore et al. isolated structurally unique cytotoxins from a lipophilic extract of Nostoc spp. GV 224. These cyclic depsipeptides called cryptophycins showed both solid tumor and tumor-selective cytotoxicity in the Corbett assay and in vivo studies revealed them to be very active against a number of tumors implanted in mice [55]. These studies may lead to the discoveries of new antitumor drags [56]. 

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