Lydiamycins A–D: Cyclodepsipetides with Antimycobacterial Properties

Out of the brew! Four new antibiotics were isolated from a fermentation broth of Steptomyces lydicus (strain HKI0343). The 13-membered-ring peptides (see formula, XY: CH2NH, CHNH; R1, R2: H, OH) are cyclized through a lactone function at serine and also contain the nonproteinogenic amino acid piperazic acid (or a derivative thereof). The peptides show promising activity against various mycobacteria without being cytotoxic.