Absolute stereochemistry and solution conformation of promothiocins

Two members of thiopeptide class antibiotics, promothiocins A and B, were previously isolated from the mycelial extract of Streptomyces sp. SF2741 as tipA promoter inducing substances. Promothiocins are unique 26-membered thiopeptides composed of valine, 2-aminomethyl-5-methyloxazole-4-carboxylic acid, 2-(1-aminoethyl)thiazole-4-carboxylic acid, 2-(2-(1-aminoethyl)-5-methyloxazolyl)-3-(4-carboxythiazolyl)pyridine-6- carboxylic acid and dehydroalanine(s). The absolute stereochemistry and solution conformation of promothiocins have been investigated by a combination of the degradation works and molecular modeling experiments. These compounds contain characteristic dehydroalanine side chains in their structures that are closely related to promoter inducing activity, but are not essential.