Synthetic studies of the bioactive natural products by using the thermal electrocyclic reaction of 6π electron systems

Abstract

We are developing the synthesis of biologically interesting condensed-heteroaromatic compounds, including natural products by the thermal electrocyclic reaction of 6π electron system incorporating the double bond of the principal aromatic or heteroaromatic ring. In this report, we describe three types of electrocyclic reactions as follows; 1) the synthesis of highly-substituted carbazole alkaloids based on the allene-mediated electrocyclic reaction involving an indole 2,3-bond, 2) the synthesis of β-carboline alkaloids and isoquinoline-5,8-quinone alkaloids based on the thermal electrocyclic reaction of an 1-azahexatriene system involving an indole 2,3-bond or benzene 1,2-bond, and 3) the synthesis of new tetracyclic pyrido [2,3-b] indole, grossularines, based on the thermal electrocyclic of an 2-azahexatriene system including the indole 2,3-bond.