[CH2:1]([O:8][C:9]([N:11]1[CH2:15][CH2:14][CH2:13][C@H:12]1C(O)=O)=[O:10])[C:2]1[CH:7]=[CH:6][CH:5]=[CH:4][CH:3]=1.[C:19](OC1C(OC(=O)C)=C(I=O)C=CC=1)(=[O:21])C.II.CO>ClCCl>[CH2:1]([O:8][C:9]([N:11]1[CH2:15][CH2:14][CH2:13][CH:12]1[O:21][CH3:19])=[O:10])[C:2]1[CH:3]=[CH:4][CH:5]=[CH:6][CH:7]=1
To a mixture of (S)-pyrrolidine-1,2-dicarboxylic acid 1-benzyl ester (purchased at Fluka, Ref 97090, 6 g, 1.0 eq.) in dichloromethane (300 mL) was added diacetoxyiodosobenzene (15.8 g, 2 eq.) and iodine (3.0 eq., 0.5 eq.). The mixture was stirred 5 h at room temperature. Methanol (12 mL) was added and the reaction mixture was stirred for an additional 1.5 h at room temperature, partitioned between an aqueous solution of sodium sulfite and dichloromethane. The organic layer was washed with an aqueous solution of sodium sulfite, brine, evaporated in vacuo and purified on silica eluting with 9:1 cyclohexane/ethyl acetate to yield 5.0 g (88%) of the desired product as light yellow oil. MS (m/e): 235.5 (MH+, 100%)
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