The chemistry of the insoluble red woods. Part 13. Synthesis of 2-(flavan-3-yl)isoflav-3-enes and of 6-benzyl-5-phenylbenzo[a]xanthens

Abstract

Methoxyisoflavylium perchlorates [type (4)] have been condensed with 3-(o-hydroxyphenyl)-1-phenylpropenes [type (5; R¹= H)] to yield products which are formulated as 2-(flavan-3-yl)isoflav-3-enes [type (6)]. Condensation of the perchlorates (4) with 3-(o-methoxyphenyl)-1-(p-methoxyphenyl)propenes [type (5; R¹= Me)] gave derivatives formulated as 6-benzyl-5-phenylbenzo[a]xanthens [type (3; R⁵= Me)], analogous to the xanthens formed from per-O-methylsantalin (1) and per-O-methylsantarubin (2) by reduction to the phenolic xanthen [type (3; R⁵= H)] and methylation.