Biosynthesis of deoxyherqueinone in Penicillium herquei from [13C]acetate and [13C]malonate. 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 [2-13C]malonate 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 [2-13C]malonate enriched 13C-n.m.r. spectrum.