451 mL ofdichloromethane, 2- (difluoro-methylthio) acetic acid 49.6 g, 144.8 mL pyridine was added to reactorand cooled to -40 ° C. (6R, 7R)-benzhydryl-7-amino-3-(chloromethyl)-7-methoxy-8-oxo-5-oxa-1-aza-bicyclo[4.2.0]oct-2-ene-2-carboxylatein dichloromethane 1080 mL was added to the reactor and temperature wasmaintained at -25 ° C. After the reactionsolution was cooled below -45 ° C, 42 mL of phosphorous oxychloride in 180.4 mLdichloromethane was added at -15°C and stirred for 30 minutes. After checking completion of the reaction1262.8 ml of purified water, 4.59 ml of 35% hydrochloric acid, 2.7 ml of 50%tetrabutylammonium bromide was added dropwise at 0°C, which in turn stirred for10 minutes. Then, 1262.8 ml of methanol was added at 0°C and stirred for 10 minutes. then separating the layer. 902 mL ethanol added to the filtrate and then stirred for 2 hours at -10 and washed with 360.8 mL of ethanol, and a white or slightly yellow horse crystal component of the vacuum-dried for 10 hours at 40 was added (6R,7R)-benzhydryl (7-(2-difluoromethylthio)acetamido)-3-(chloromethyl)-7-methoxy-8-oxo-5-oxa-1-aza-bicyclo[4,2,0]oct-2-ene-2-carboxylate (146.7g, 76%).
