The structure of inducing factors for virginiamycin production in Streptomyces virginiae

Virginiamycin inducing factors (inducing material or inducing factor) of Streptomyces virginiae were isolated from the culture broth of this microbe and separated into three closely related compounds. They were named virginiae butanolides A, B and C and their structures were determined as 2-(1'-hydroxy-5'-methylhexyl)-3-(hydroxymethyl)butanolide (6), 2-(1'-hydroxy-4'-methylhexyl)-3-(hydroxymethyl)butanolide (7) and 2-(1'-hydroxyhexyl)-3-(hydroxymethyl)butanolide (8), respectively. Part of their stereochemistry was also determined. Racemic virginiae butanolide C was synthesized to confirm their structures.