Triethylamine → 3-Methanesulfonyloxy-1-[4-(3-methoxyazetidine-1-carbonyl)-1,3-oxazol-2-yl]azetidine

To a solution of 3-hydroxy-1-[4-(3-methoxyazetidine-1-carbonyl)-1,3-oxazol-2-yl]azetidine (480 mg, 1.89 mmol) (obtained as described in Reference Example 73(2)) in methylene chloride (24 ml) were added methanesulfonyl chloride (439 μl, 5.67 mmol) and triethylamine (795 ml, 5.67 mmol) in an ice bath and the mixture was stirred for 10 minutes and then at room temperature for 30 minutes. After checking the completion of the reaction, the mixture was partitioned between ethyl acetate and saturated aqueous sodium hydrogencarbonate solution. The organic layer was washed with saturated aqueous sodium chloride solution, dried over anhydrous sodium chloride, filtered and concentrated under reduced pressure. To the residue were added ethyl acetate and diisopropyl ether to give a solid and the solid was collected by filtration, washed with diisopropyl ether to afford 3-methanesulfonyloxy-1-[4-(3-methoxyazetidine-1-carbonyl)-1,3-oxazol-2-yl]azetidine (586 mg, yield 94%) as a pale yellow solid.