The synthesis of pacharin: a dibenzoxepine from the heartwood of Bauhinia racemosa Lamk.

Abstract

The synthesis of the novel dibenzoxepine derivative pacharin (13)(8-methoxy-7-methyldibenz[b,f]-oxepine-1,6-diol), a constituent of the heartwood of Bauhinia racemosa Lamk., is described The route depended on the formation of the diphenyl ether (8) which was converted by standard synthetic steps into the bisphosphonium salt (11). The derived bis-ylide underwent oxidative cyclization to the dibenzoxepine (12) which gave pacharin (13) on deprotection.