To a solution of 4.30 g (0.022 mole) of 98% p-toluenesulfonyl chloride in 24 ml of anhydrous pyridine at 0° (ice bath) was added 2.64 g (0.011 mole) of cis-2-hydroxymethyl-4-oxo-3-phenoxyacetylaminoazetidine in one portion. The solution was stirred at 0° for 3 hours then was stored at -25° overnight. After warming to 0°, 1.0 ml of 85% lactic acid was added and stirring was continued for 1 hour. The reaction mixture was poured into ethyl acetate and extracted successively with water, dilute aqueous hydrochloric acid, aqueous sodium bicarbonate and brine and was dried (MgSO4). Filtration followed by removal of the solvent in vacuo resulted in a yellow solid. Clarification of a hot solution of this material in ethyl acetate (375 ml), followed by the addition of hexane (200 ml) and recrystallization afforded cis-4-oxo-3-phenoxyacetylamino-2-p-toluenesulfonyloxymethyl-azetidine; tlc: ethyl acetate, silica gel GF, Rf = 0.47; mp 136°(dec.).
