Enantioselective total synthesis of (+)-stachyflin: A potential anti-influenza a virus agent isolated from a microorganism

Abstract

A novel and potent hemagglutinin inhibitor, (+)-stachyflin, was efficiently synthesized in an enantioselective manner starting from the (+)-5-methyl-Wieland-Miescher ketone. The synthetic method features a BF 3·Et2O-induced cascade epoxide-opening/ rearrangement/cyclization reaction tostereoselectively construct the requisite pentacyclic ring system in one step. In order to rationalize the mechanism of the cascade reaction, quantum chemical calculations of the possible intermediary carbocations and transition states in the model synthesis were carried out. An alternative approach to synthesize (+)-stachyflin by employing a similar cascade reaction was also described. A potential anti-influenza A virus agent, (+)-stachyflin, a novel hemagglutinin inhibitor, has been synthesized in an enantioselective manner for the first time starting from (+)-5-methyl-Wieland- Miescher ketone. The method features a BF3·Et 2O-induced cascade epoxide-opening/rearrangement/cyclization reaction to construct the requisite pentacyclic ring system in one step. © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.