In the course of screening for apoptosis-inducing agents, chloptosin (1) was isolated from the culture broth of Streptomyces. The dumbbell-type structure of the dimeric cyclohexapeptide consisting of D-valine, (3S)- and (3R)-piperazic acids, O-methyl-L-serine, D-threonine, and (2S,3aR,8aR)-6-chloro-3a-hydroxy-2,3,3a, 8a-hexahydropyrrolo[2,3-b]indole-2-carboxylic acid was elucidated by spectroscopic and chemical degradation studies. The amino acid components in each cyclohexapeptide domain were presented in alternating R and S configurations. Chloptosin (1) was found to induce apoptotic activity in apoptosis-resistant human pancreatic adenocarcinoma cell line AsPC-1 and showed a strong antimicrobial activity against Gram-positive bacteria including methicillin-resistant Staphylococcus aureus.

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