A solution of allyl (1S,5R,6S)-6-[1(R)-allyloxycarbonyloxy-ethyl]-2-hydroxymethyl-1-methyl-carbapen-2-em-3-carboxylate (60 mg, 0.164 mmol), 1-methyl-1,3-dihydro-2-thia-1,3-diaza-cyclopenta[b]naphthalene 2,2-dioxide (42 mg, 0.180 mmol), and triphenylphosphine (65 mg, 0.246 mmol) in anhydrous tetrahydrofuran (1 mL) was cooled in an ice bath and treated with diisopropyl azodicarboxylate (0.049 mL, 0.246 mmol). The mixture was stirred at 0-5° C. for 30 minutes, then streaked onto two 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]-1-methyl-2-(3-methyl-2,2-dioxo-2,3-dihydro-2-thia-1,3-diaza-cyclopenta[b]naphthalen-1-yl-methyl)-carbapen-2-em-3-carboxylate (52 mg) as an oil.
