Stereoselective total synthesis of testosterone and androsterone viaA/B-ring construction of the steroidal ring system by intramolecular Diels–Alder reaction

Abstract
The optically active indandione (8) was stereoselectively converted into the (E)-triene (23), which was subjected to an intramolecular Diels–Alder reaction to give quantitatively A/B-trans and A/B-cis isomers (24) and (26) in ratios of 4 : 1 and 3.8 : 1. The cycloadduct (24) was transformed into testosterone (4) and androsterone (5).