Benzothiazines in synthesis. A total synthesis of pseudopteroxazole

An enantioselective total synthesis of the naturally occurring antitubercular agent pseudopteroxazole is described. The synthesis is organized around the use of a stereoselective, intramolecular addition of a sulfoximine carbanion to an alpha,beta-unsaturated ester to form an enantionterically pure benzothiazine. Other important processes include a completely stereoselective intramolecular Friedel-Crafts alkylation and a stereoselective and regioselective hydrogenation.