A novel synthetic approach to isoatisirene-related compounds via an intramolecular Diels-Alder reaction

Abstract

A new synthesis of 2-oxo-18-norisoatisirene (2), a potential intermediate for the synthesis of isoatisirene (1), via 3-methoxy-7-methyl-9-phenylthio-4bβ,5,6,8a,9,10-hexahydro-6α,8aα-ethanophenanthren-8(7H)-one (4a) and 3-methoxy-7-methyl-7-phenylthio-4bβ,5,6,7,8,8a,9,10-octahydro-6α,8aα-ethanophenanthrene (4b)[which were prepared by a thermolysis of 5-methoxy-1-(2-methyl-3-oxo-4-phenylthiomethylenecyclohexylmethyl)-1,2-dihydrocyclobutabenzene (6a), and 5-methoxy-1-(2-methyl-4-methylenecyclohexylmethyl)-1,2-dihydrocyclobutabenzene (6b) respectively] is described.