Improved,rapid and efficient synthesis of poly-methoxyflavones under microwave irradiation and their inhibitory effects on melanogenesis

摘要

The microwave-assisted methylation of 2,5-dihydroxy-l,3-dimethoxybenzene with (CH_3O)_2SO_2 for 5 min gave easily 1,2,3,5-tetramethoxybenzene, which was converted into pentamethoxybenzene. The microwave-assisted Friedel-Crafts acylation of pentamethoxybenzene in the presence of In(CF_3SO_3)_3 gave pentamethoxyacetophenone for 15 min under solvent-free conditions in high yield. The microwave-assisted cyclization reaction of the diketones, which were synthesized from the acetophenone via three steps under microwave irradiation, gave the desired polymethoxyflavones for 1.5-3 min in high yields. The polymethoxyflavones showed inhibitory effects on melanogenesis in a human melanoma.