Total synthesis of sophorapterocarpan A, maackiain, and anhydropisatin: application of a 1,3-Michael-Claisen annulation to aromatic synthesis

Abstract

A new synthetic route to the pterocarpans using a [3C + 3C] annulation is described. 1,3-Michael-Claisen condensation of α-methylene-γ-butyrolactones with α-sulphur-substituted ketones gives 6-membered rings which have been converted into the pterocarpan framework by aromatization. Sophorapterocarpan A, maackiain, and anhydropisatin have been prepared employing this new aromatic synthesis.