Stereoselective synthesis of anti-beta-amino-alpha-hydroxy acid derivatives using nucleophilic epoxidation of 1-arylthio-1-nitroalkenes

Reaction of lithium t-butylperoxide with 1-arylthio-1-nitroalkenes 5, prepared by condensation of (4-tolylthio)nitromethane with N-(Boc)-protected alpha-amino aldehydes, leads to the formation of oxazolidinones rather than the expected oxiranes. Initially. a mixture of c's 8 and trans 9 diastereoisomers is formed, but upon exposure to silica gel complete conversion to the cis-diastereoisomers 8 takes place.