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.