Carbon‐13 nuclear magnetic resonance studies of anthraquinones Part II—hydroxymethoxyanthraquinones, acetoxymethoxyanthraquinones and naturally occuring anthraquinone analogues

The 13 C NMR spectra of hydroxymethoxyanthraquinones, acetoxymethoxyanthraquinones and naturally occuring anthraquinone derivatives are reported and all chemical shifts assigned. Hydroxy, methoxy and acetoxy substitution parameters are additive except in the case of 1,2‐disubstitution and for 1‐hydroxyanthraquinones substituted on C‐3 or on C‐4 by an hydroxy or a methoxy group. In anthraquinones substituted on C‐2, carbon shieldings are found to be sensitive to steric interference and to conjugative electron release by the 1‐OCH 3 .