Efficient Synthesis of Bibenzyl Derivatives Bearing Pyranyl Moieties: First Total Synthesis of Bauhinol D

Abstract

An efficient and general synthesis of bibenzyl derivatives bearing pyranyl rings was achieved by ethylenediamine diacetate-catalyzed reactions of 3,5-dihydroxybibenzyl with α,β-unsaturated aldehydes in moderate yields. These reactions provided naturally occurring compounds 1 and 2 in single step reaction. As an application of this methodology, biologically interesting natural bauhinol D (8) was synthesized by a convergent sequence from readily available benzaldehyde and benzyl phosphonate.

Total Synthesis of Phytotoxic Radulanin A Facilitated by the Photochemical Ring Expansion of a 2,2-Dimethylchromene in Flow

“…This nucleophilic diphenol was engaged in the formation of chromene 3 in the presence of prenal and the Brønsted acid catalyst EDDA (Scheme 2). 19,24 On a practical point of view, adding EDDA in three portions of 5 mol% over three hours furnished the best yields of 3 (82%), which was accompanied by a small amount of regioisomer 18 (3%). Compound 18 is also a natural product found in Radula species.…”