Stereoselective nucleophilic epoxidation of protected 3-amino and 3-hydroxy-substituted 1-arylthio-1-nitroalkenes, followed by intramolecular capture involving the amino and hydroxyl protecting groups, has led to the formation of isomeric oxazolidinones 5 and 7, and a cyclic carbonate 11. Together with the oxazolidinone precursor anti-alpha-bromo thioester 15a, the absolute and relative stereochemistry of these compounds has been determined by X-ray crystallography.