Dimethylformamide → Tetrabutylammonium (2S,3S)-3-{[(benzyloxy)carbonyl]amino}-2-methyl-4-oxoazetidine-1-sulfonate

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Reaction Steps

A solution of 600 mg of (3S-trans)-3-benzyloxycarbonylamino-4-methylazetidinone in 2 ml of dimethylformamide was cooled to 0° C. and 4 ml of 0.8M sulfur trioxide in dimethylformamide was added. The solution was stirred at room temperature under nitrogen for 1 hour and poured into 80 ml of cold 0.5M monobasic potassium phosphate (adjusted to pH 5.5). The solution was extracted with three 50 ml portions of methylene chloride (discarded) and 868 mg of tetrabutylammonium bisulfate was added. The resulting solution was extracted with four 75 ml portions of methylene chloride. The combined organic layer was washed with 8% aqueous sodium chloride, dried, and evaporated in vacuo yielding 1.54 g of the title compound.

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