The biosynthesis of fungal metabolites. Part II. The β-oxo-lactone equivalents in rubropunctatin and monascorubrin

Abstract

Incorporations of diethyl [1-¹⁴C]malonate by Monascus purpureus Wentii into rubropunctatin (III; R = C₅H₁₁) and monascorubrin (III; R = C₇H₁₅) have shown that the main poly-β-ketide chain of these metabolites is assembled from acetate plus malonate in the normal way. However, the β-oxo-lactone systems are derived by condensation of hexanoate and octanoate, respectively, with acetate. Although malonate is utilised in the normal way in the derivation of these fatty acid equivalents, it is not involved in the conversion of these into β-oxo-decanoate and β-oxo-octanoate equivalents, respectively. A probable explanation of these results is suggested.