The total structure of the antibiotic longicatenamycin

The peptide antibiotic longicatenamycin produced by a Streptomyces strain S-520 is a complex mixture of several congeners. The determination of the total structure of longicatenamycin was performed on the mixture using the procedure of N-bromosuccinimide oxidation followed by EDMAN degradation. The structure of the most abundant congener of longicatenamycin can be represented as cyclo (glycyl-L-2-amino-6-methylheptanoyl-D-valyl-D-ornithyl-threo-beta-hydroxy-L-glutamyl-5-chloro-D-tryptophyl) (Fig. 1: 1=4, m=0, n=3). There are three amino acid positions in which variations are found. The antibiotic complex contains compounds in which L-2-amino-6-methyl-heptanoic acid is replaced with either L-2-amino-5-methylhexanoic acid of L-2-amino-7-methyloctanoic acid; further D-valine with D-isoleucine as well as D-ornithine with D-lysine.