Complete assignment of the C-13 NMR spectra of a series of 5,8-disubstituted 4,4-dimethylanthracene-1,9,10(4H)-triones

Abstract

The regiosomeric quinones 5-acetyloxymethyl-4,4,8-trimethyl- (5) and 8-acetyloxymethyl-4,4,5-trimethylanthracene-1,9,10(4H)-trione (6) were synthesized and their regiochemistry was assigned on the basis of the unambiguous structure elucidation of 9,10-dihydroxy-5-acetyloxymethyl-4,4,8-trimethyl-5,8-dihydroanthracen-1(4H)-one (2), the precursor of 5. The H-1 and C-13 NMR spectra of these compounds were assigned completely using two-dimensional techniques. These interpretations were used for the total assignment of the NMR spectra of the closely related 5-hydroxymethyl- and 5-formyl-4,4,8-trimethylanthracene-1,9,10(4H)-triones (7 and 8, respectively).