Antibiotics from gliding bacteria, LXXXIII - The crocacins, novel antifungal and cytotoxic antibiotics from Chondromyces crocatus and Chondromyces pediculatus (Myxobacteria): Isolation and structure elucidation

Four novel antifungal and highly cytotoxic metabolites, the crocacins A-D ( 1-4), were isolated in our screening of the myxobacterial genus Chondromyce s from strains of C. crocatus and C. pediculatus. Crocacin A, B, and D (1, 2, and 4) are unusual dipeptides of glycine and a 6-aminohexenoic or -hexad ienoic acid, which is N-protected by a complex polyketide-derived acyl resi due. The latter is a multiply substituted phenylundecatrienoic acid, which is found as its primary amide crocacin C (3). Based on H-1 coupling constan ts, NOEs and MM+ calculations the relative configuration of the asymmetric centers and their preferred conformation are proposed for the crocacins.