Antifertility agents: a synthetic entry to yuehchukene analogues; stereoselective synthesis of 7,7-bis-nor-yuehchukene via 9-methyl-6-oxo-6aβ-7,8,10aβ-tetrahydroindeno[2,1-b]indole

Abstract

Intermolecular Diels–Alder reaction and polyphosphate ester-catalysed intramolecular acylation are used in a synthetic approach to 9-methyl-6-oxo-6aβ-7,8,10aβ-tetrahydroindeno[2,1-b] indole (15), the basic structure of the antifertility agent yuehchukene (1). Stereoselective conversion of (15) into 7,7-bis-nor-yuehchukene (19) is also described.