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Note | Regular issue | Vol 60, No. 12, 2003, pp.2775-2784
Published online, 14th October, 2003
DOI: 10.3987/COM-03-9891
Improved, Rapid and Efficient Synthesis of Polymethoxyflavones under Microwave Irradiation and Their Inhibitory Effects on Melanogenesis

Masao Tsukayama,* Yasuhiko Kawamura, Takaaki Ishizuka, Shinji Hayashi, and Fumihito Torii

*Department of Chemical Science and Technology, Faculty of Engineering, University of Tokushima, Minamijosanjima-cho, Tokushima 770-8506, Japan

Abstract

The microwave-assisted methylation of 2,5-dihydroxy-1,3-dimethoxybenzeneÅ@with (CH3O)2SO2 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(CF3SO3)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.