Biosynthesis of deoxyherqueinone in Penicillium herquei from 13Cacetate and 13Cmalonate. Assembly pattern of acetate into the phenalenone ring system

The 13C n.m.r. spectra of deoxyherqueinone (I) enriched with sodium 1-13C-, 2-13C-, and 1,2-13C2- acetate, and diethyl 2-13Cmalonate by the fungus Penicillium herzuei indicate formation of the phenalenone ring system from seven intact acetate units and the mode of folding of the precursor heptaketide chain; a clear acetate ‘starter’ effect is apparent in the 2-13Cmalonate enriched 13C-n.m.r. spectrum.