Structural Studies on Herqueinone. The Configurations at C-4 of Herqueinone and at C-3 and C-4 of Dihydroherqueinone Monomethyl Ether

On the basis of the 1H NMR spectroscopy and the X-ray crystallography, the configuration at C-4 of herqueinone was determined to be S and the configurations at C-3 and C-4 of dihydroherqueinone monomethyl ether were elucidated to be R and S, respectively, with relation to the previously established R-configuration at the 2′-position of herqueinone.