A total synthesis of (±)-5β, 8α-androst-9 (11)-ene-3, 17-dione is described. The key step is a ring C forming SnCl4-catalyzed Diels-Alder reaction in which the geometry of the diene controls syn-anti stereochemistry while the catalyst guides the addition to the desired endo orientation. A preparation of ethyl E-2-methyl-4-oxo-2-butenoate and the dehydration of a tertiary allylic alcohol by the pyrolysis of the corresponding tosyl carbamate are also ...
