Isolation of cairomycins A and C.

Cairomycin B in the fermentation broths of Streptomyces sp. strain AS-C-19 accompanied cairomycin A and cairomycin C. The cairomycins are peptides with potent activity against gram-positive bacteria. On acid hydrolysis, cairomycin A yielded valine and aspartic acid, whereas cairomycin C yielded lysine, glycine, valine, leucine, and aspartic acid, as identified by paper and gas chromatography. These amino acids were found to exist in their alpha-L form. Cairomycin A was tentatively assigned a 6-isopropyl-2,5-diketopiperazine-3-acetic acid structure. The three cairomycins were distinct from each other in their ultraviolet, infrared, and mass spectra; elemental analyses; and their chromatographic behavior in different developing solvents.