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One-pot synthesis of the tetracyclic framework of the aromatic erythrina alkaloids from simple furans.

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 N-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.