One-pot Synthesis of the Tetracyclic Framework of the Aromatic <i>Erythrina</i> Alkaloids from Simple Furans

Abstract

Conversion of a simple furan into the intact erythrinane skeleton in one synthetic operation has been accomplished. The one-pot reaction sequence begins with singlet oxygen photooxygenation of the furan and proceeds via a 2-pyrrolidinone formation, cyclization of the pendant aldehyde moiety and an <i>N</i>-acyliminium ion formation and terminates with a Pictet-Spengler-type aromatic substitution. The method has been used to achieve a rapid and highly effective formal synthesis of erysotramidine