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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 2-13Cmalonate indicate formation of the phenalenone ring system via a specific folding of a single heptaketide chain.
Thomas J. Simpson (Mon,) studied this question.