The novel gluconeogenesis inhibitors FR225659 and FR225656 from Helicomyces sp No. 19353 III.: Structure determination

During the course of screening for novel gluconeogenesis inhibitors, FR225659 and its related compounds were isolated from a fermentation broth of Helicomyces sp. No. 19353. Spectroscopic analysis concluded that FR225659 is an N-acyl tripeptide consisting of a novel acyl, a 3-chloro-4-hydroxyarginine, a 3-hydroxy-3-methylproline and a dehydrovaline. Degradation study allowed assignment of the absolute configuration of the 3-hydroxy-3-methylproline to be (2S,3R). FR225656 was shown to possess a dehydroisoleucine instead of the dehydrovaline of FR225659.