[CH3:1][S:2](Cl)(=[O:4])=[O:3].C(OC([N:13]1[CH2:17][CH2:16][C@H:15]([OH:18])[C@H:14]1[C:19](=[O:24])[N:20]([O:22][CH3:23])[CH3:21])=O)(C)(C)C.C(N(CC)CC)C>ClCCl>[CH3:23][O:22][N:20]([CH3:21])[C:19]([CH:14]1[CH:15]([O:18][S:2]([CH3:1])(=[O:4])=[O:3])[CH2:16][CH2:17][NH:13]1)=[O:24]Methane sulphonyl chloride (3.49 g) was added dropwise over 10 minutes to a mixture of compound 65 (7.6 g) and triethylamine (7.7 ml) in dichloromethane (350 ml) and cooled to 0° C. under an argon atmosphere. It was then stirred at 0° C. for another hour. The reation mixture was then applied directly to a silica flash column which was eluted with ethyl acetate to give (2S,3 S)-1-tert-butoxycarbonyl)-2(N-methoxy-N-methylcarbamoyl)-3-methansulfonyloxypyrrolidine (compound 66) as a gum (9.7 g).
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