C(Cl)(=O)C(Cl)=O.CS(C)=O.[C:11]([O:15][C:16]([N:18]1[CH2:26][CH:25]2[CH:20]([CH2:21][CH2:22][CH:23]([OH:27])[CH2:24]2)[CH2:19]1)=[O:17])([CH3:14])([CH3:13])[CH3:12].C(N(CC)CC)C>ClCCl>[C:11]([O:15][C:16]([N:18]1[CH2:26][CH:25]2[CH:20]([CH2:21][CH2:22][C:23](=[O:27])[CH2:24]2)[CH2:19]1)=[O:17])([CH3:14])([CH3:12])[CH3:13]4.9 g of oxalyl chloride was dissolved in 250 ml of dichloromethane and cooled to −78° C. in a nitrogen atmosphere. Then a solution of 4.83 g of dimethyl sulfoxide in dichloromethane (20 ml) was dropped thereinto over 17 minutes. Subsequently, a solution of 3.73 g of 8-(tert-butoxycarbonyl)-8-azabicyclo[4.3.0]nonan-3-ol in dichloromethane (40 ml) was dropped thereinto over 10 minutes. After stirring for 10 minutes, 7.82 g of triethylamine was dropped thereinto over 10 minutes and stirring was continued for additional 1 hour. The reaction mixture was brought back to room temperature, diluted with dichloromethane, washed with water and a saturated aqueous solution of sodium chloride and then dried over anhydrous magnesium sulfate. After filtration, the solvent was distilled off under reduced pressure. The residue thus obtained was purified by silica gel column chromatography (eluted with n-hexane/ethyl acetate) to thereby give 3.21 g of the title compound as a colorless oily substance.
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