Synthesis and structural elucidation of 2,3-dimethylnaphthazarin ester derivatives

Abstract

A simple and efficient synthesis of bis-ester substituted 2,3-dimethylnaphthazarins is described. The preparation of 5-O,8-O-bis-ester derivatives of 2,3-dimethylnaphthazarin was achieved via double esterification reaction of 5,8-dihydroxy-2,3-dimethylnaphthazarin with a range of acyl chlorides under mild reaction conditions. Additionally, 5-O- mono ester and unsymmetrical 5-O,8-O-bis-ester derivatives of 2,3-dimethylnaphthazarins were successfully synthesized. The identities of new compounds were confirmed by H-1 NMR, C-13 NMR, FTIR, HRMS and X-ray single-crystal diffraction techniques.