A New Synthesis of Polyhydroxydihydroflavonols

An alkaline hydrogen peroxide oxidation of chalcones with methoxymethoxyl groups in the 2′-position and in other positions gave the corresponding poly(methoxymethoxy)chalcone oxides; these were then, in turn, easily converted into polyhydroxydihydroflavonols, with a simultaneous splitting of all the O-methoxymethyl groups, by warming with acid. The general applicability of the new method was illustrated by the synthesis of the following hydroxydihydroflavonols: 3,7-dihydroxy- (m.p. 170–171°C),3,4′-dihydroxy- (m.p. 214–216°C),3,4′-dihydroxy-3′-methoxy- (m.p. 217–218°C),3,4′,7-trihydroxy- (m.p. 214–215°C), and 3,3′,4′,7-tetra-hydroxyflavanone (dl-fustin, m. p. 217–218°C). The first four new compounds were identified by converting them into known methyl ethers, while the last one was identified by comparing it with natural dl-fustin. Their structures were also confirmed by infrared and ultraviolet spectra.