| Abstract
| - Three potent cancer cell cytotoxins, piperazimycins A−C (1−3), have been isolated from the fermentationbroth of a Streptomyces sp., cultivated from marine sediments near the island of Guam. The structuresof these cyclic hexadepsipeptides were assigned by a combination of spectral, chemical, and crystallographic methods. The piperazimycins are composed of rare amino acids, including hydroxyacetic acid,α-methylserine, γ-hydroxypiperazic acid, and γ-chloropiperazic acid. The novel amino acid residues2-amino-8-methyl-4,6-nonadienoic acid and 2-amino-8-methyl-4,6-decadienoic acid were found ascomponents of piperazimycins A and C, respectively. When screened in the National Cancer Institute's60 cancer cell line panel, piperazimycin A exhibited potent in vitro cytotoxicity toward multiple tumorcell lines with a mean GI50 of 100 nM.
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