Total synthesis of tubastrine and 3-dehydroxy tubastrine by microwave-assisted cross-coupling reactions

Abstract

The first syntheses of tubastrine and 3-dehydroxy tubastrine are described. The target compounds were prepared in four consecutive steps from commercially available starting materials. The central scaffold was formed by a microwave-assisted C–N cross-coupling reaction between 1,3-bis(tert-butoxycarbonyl)-guanidine and (E)-((4-(2-iodovinyl)-1,2-phenylene)bis(oxy))bis(tert-butyldimethylsilane) and (E)-tert-butyl(4-(2-iodovinyl)phenoxy)–dimethylsilane, respectively. The aryl vinyl iodides were obtained by a Hunsdiecker–Borodin-type reaction of aryl acrylic acids, which were easily available from trans-caffeic acid or trans-p-coumaric acid.