A FACILE CONVERSION OF THE PHENYLTHIO GROUP TO ACETOXY BY COPPER REAGENTS FOR A PRACTICAL SYNTHESIS OF 4-ACETOXYAZETIDIN-2-ONE DERIVATIVES FROM (R)-BUTANE-1,3-DIOL

(3S,4R,1'R)-4-Acetoxy-3-(1'-tert-butyldimethylsilyloxyethyl)-azetidin-2-one 8, an important intermediate for the synthesis of penem and carbapenem antibiotics, was synthesized from (R)-butane-1,3-diol 1, using chlorosulphonyl isocyanate for the formation of beta-lactam ring in which a significant solvent effect on the ratio of diastereoisomers 6a and 6b was observed; copper(II) acetate rather than the poisonous mercury(II) acetate was used to convert the phenylthio group of compound 6a to acetoxy.