A solution of allyl (1S,5R,6S)-6-[1(R)-allyloxycarbonyloxyethyl]-2-hydroxymethyl-1-methyl-carbapen-2-em-3-carboxylate (25.5 mg, 0.07 mmol), 1,3-dihydro-benzo[c]isothiazole 2,2-dioxide (13 mg, 0.077 mmol), and triphenylphosphine (28 mg, 0.105 mmol) in anhydrous tetrahydrofuran (0.4 mL) was cooled in an ice bath and treated with diethyl azodicarboxylate (0.017 mL, 0.105 mmol). The mixture was stirred at 0-5° C. for 30 minutes, then streaked onto a 1 mm×20 cm×20 cm silica gel GF plates. The plates were developed with 5% ethyl acetate in dichloromethane. The product band was removed and eluted with ethyl acetate to afford allyl (1S,5R,6S)-6-[1(R)-allyloxycarbonyloxy-ethyl]-2-(2,2-dioxo-2,3-dihydro-benzo [c]isothiazol-1-yl-methyl)-1-methyl-carbapen-2-em-3-carboxylate (15 mg) as an oil.
