Biosynthesis of palitantin, a polyketide metabolite of Penicillium brefeldianum: 13C n.m.r. assignment and incorporation of 13C-, 2H-, and 18O2-labelled acetates

Abstract

The biosynthesis of palitantin (1), a metabolite of Penicillium brefeldianum, has been studied using sodium [1,2-¹³C₂]-, [2-²H₃]-, [2-¹³C,2-²H₃]-, and [1-¹³C,1-¹⁸O₂]-acetate as simple precursors. Analysis of the labelled products by both n.m.r. and mass spectrometry established that no aromatic intermediates are involved in the generation of the six-membered carbocyclic ring. The assignment of the ¹H and ¹³C n.m.r. spectra was made with the aid of two-dimensional homonuclear correlation experiments as well as more standard techniques. Incidentally, O-methyl fulvic acid (2) and O-methyl anhydrofulvic acid (3) were discovered as metabolites of P. brefeldianum.