PHOTOOXIDATIVE CLEAVAGE OF A FURAN-AZETIDINONE CARBON-CARBON BOND - ASYNTHESIS OF 4-ACETOXYAZETIDINONE

A stereoselective synthesis of the 4-acetoxyazetidinione(1)from methyl 3(R)-hydroxybutyrate is reported. The synthesis involved stereoselect ive preparation of a 4-(2-furanyl)azetidinone that was allowed to reac t with singlet oxygen. The resulting endoperoxide intermediates underw ent direct rearrangement to an acyloxyazetidinone that on reaction wit h sodium acetate gave 1 in modest yield. An improved yield of 1 was ob tained by treatment of the endoperoxides with hydrogen peroxide follow ed by acetic anhydride to give an alpha-alkoxy acylperoxide that under went thermal rearrangement to 1.