C-13 NUCLEAR MAGNETIC-RESONANCE STRUCTURAL AND BIOSYNTHETIC-STUDIES ON DEOXYHERQUEINONE AND HERQUEICHRYSIN, PHENALENONE METABOLITES OF PENICILLIUM-HERQUEI

A detailed analysis of the 13C-1H couplings observed in the fully 1H-coupled 13C n.m.r. spectrum of deoxyherqueinone diacetate allow its structure to be defined as (3) and a full assignment of the 13C n.m.r. spectrum to be made. The structure of herqueichrysin triacetate (8) is established by analysis of 13C- 1H couplings in the fully 1H-coupled, natural abundance 13C n.m.r. spectrum, and 13C-13C couplings in the [1,2-13C2]acetate enriched 13C n.m.r. spectrum. Further chemical and spectral studies allow structure (9) to be proposed for herqueichrysin. Incorporations of sodium [1-13C]-, [2-13C]-, and [1,2-13C2]-acetate, and diethyl [2-13C]malonate indicate formation of the phenalenone ring system via a specific folding of a single heptaketide chain.