10. シリカゲルを用いた超音波照射下でのフラボノイドの合成

抄録

Various epoxy flavanes substituted with methyl and methoxy groups were reacted with silica gel (230-400 mesh) under ultrasonic irradiation(Sus-4005C, 50W, 40kHz) for 1h to give the corresponding 3-hydoxyflavanes in good yields(ca.80-98%). When epoxy 3- hydroxyflavanes were reacted with silica gel only with stirring at 40 C in 12h, the yields were in ca.50-70 %. Epoxy flavanes were synthesized by oxidation of 2-cinnamyl substituted phenols with m- CPBA in methylene chloride. Epoxy flavanes were synthesized from the corresponding substituted phenols and cinnamyl alcohol with zinc chloride in benzene under reflux for 24h. For the formation of C-ring of flavane from epoxy compound, this ultrasonic method was useful in comparing with stirring only.