RESUMO
A biomimetic total synthesis of santalinâ Y, a structurally complex but racemic natural product, is described. The key step is proposed to be a (3+2)â cycloaddition of a benzylstyrene to a "vinylogous oxidopyrylium", which is followed by an intramolecular Friedel-Crafts reaction. This cascade generates the unique oxafenestrane framework of the target molecule and sets its five stereocenters in one operation. Our work provides rapid access to santalinâ Y and clarifies its biosynthetic relationship with other colorants isolated from red sandalwood.
Assuntos
Benzopiranos/síntese química , Produtos Biológicos/síntese química , Compostos Heterocíclicos de 4 ou mais Anéis/síntese química , Benzopiranos/química , Produtos Biológicos/química , Biomimética , Cristalografia por Raios X , Reação de Cicloadição , Compostos Heterocíclicos de 4 ou mais Anéis/química , Conformação Molecular , EstereoisomerismoRESUMO
A short total synthesis, guided by biosynthetic considerations, of racemic merochlorin B is presented. The formation of its isomer, merochlorin A, was not observed under the conditions. Key steps include a directed ortho-metalation (DoM), a selective demethylation, an ortho-allylation, and an oxidative [3 + 2]-cycloaddition mediated by an iodine(III) reagent.