[CH2:1]([O:3][C:4]([C:6]1[N:7]=[C:8]([N:11]2[CH2:15][CH2:14][C@@H:13]([OH:16])[CH2:12]2)[S:9][CH:10]=1)=[O:5])[CH3:2].[CH3:17][S:18](Cl)(=[O:20])=[O:19].C(N(CC)CC)C.C(O)C>C(Cl)Cl>[CH2:1]([O:3][C:4]([C:6]1[N:7]=[C:8]([N:11]2[CH2:15][CH2:14][C@@H:13]([O:16][S:18]([CH3:17])(=[O:20])=[O:19])[CH2:12]2)[S:9][CH:10]=1)=[O:5])[CH3:2]
To a solution of (3R)-1-(4-ethoxycarbonyl-1,3-thiazol-2-yl)-3-hydroxypyrrolidine (970 mg, 4.00 mmol) (obtained as described in Reference Example 18(2)) in methylene chloride (30 ml) were added methanesulfonyl chloride (1.24 ml, 16.0 mmol) and triethylamine (2.24 ml, 16.0 mmol) in an ice bath, and then the mixture was stirred for 1 hour. After checking the completion of the reaction, ethanol (0.81 ml) was added thereto and then the resulting mixture was stirred at room temperature for 30 minutes. The reaction mixture was partitioned between ethyl acetate and saturated aqueous sodium hydrogencarbonate solution. The organic layer was washed with saturated aqueous sodium chloride solution, dried over anhydrous sodium sulfate, filtered and concentrated under reduced pressure. The residue was purified by chromatography on a silica gel column using toluene:acetonitrile (4:1→1:1) as the eluant to afford (3R)-1-(4-ethoxycarbonyl-1,3-thiazol-2-yl)-3-methanesulfonyloxypyrrolidine (1.00 g, yield 78%) as a pale yellow solid.
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