Cyclodepsipeptides from Beauveria bassiana. Part 2. Beauverolides A to F and their relationship to isarolide

Abstract

In some fermentations with a Beauveria bassiana strain capable of producing beauverolides A–F, the beauverolide metabolites contain alloisoleucine residues in place of isoleucine and are designated by the subscript a. Beauverolides E_a and F_a are shown to be the cyclotetradepsipeptides cyclo-[3-hydroxy-4-methyloctanoyl-L-valyl-L-phenylalanyl-D-alloisoleucyl] and cyclo-[3-hydroxy-4-methyloctanoyl-L-phenylalanyl-L-phenylalanyl-D-alloisoleucyl] respectively. Beauverolides B_a and C_a are the homologues derived from 3-hydroxy-4-methyldecanoic acid. Beauverolide B_a is identical with Isarolide A and with beauverilide A. Beauverolide C_a is identical with Isarolide C. The structures of beauverolides A and D are deduced from the mass spectra of the beauverolide mixture.