[CH2:1]([O:3][C:4]([C@@H:6]1[C@@H:11]2[C@H:7]1[CH2:8][C:9](=[O:25])[C@@:10]2([N:22]=[N+:23]=[N-:24])[C:12]([O:14][CH2:15][C:16]1[CH:21]=[CH:20][CH:19]=[CH:18][CH:17]=1)=[O:13])=[O:5])[CH3:2].[BH4-].[Na+].Cl>CCO.C1COCC1>[CH2:1]([O:3][C:4]([C@@H:6]1[C@@H:11]2[C@H:7]1[CH2:8][C@H:9]([OH:25])[C@@:10]2([N:22]=[N+:23]=[N-:24])[C:12]([O:14][CH2:15][C:16]1[CH:21]=[CH:20][CH:19]=[CH:18][CH:17]=1)=[O:13])=[O:5])[CH3:2]To a solution of (1S,2R,5R,6S)-2-azido-3-oxo-bicyclo[3.1.0]hexane-2,6-dicarboxylic acid 2-benzyl ester 6-ethyl ester (IX-1) (100 mg, 0.29 mmol) in EtOH (1.7 mL) and THF (0.5 mL) was added NaBH4 (22 mg, 0.58 mmol) at -50° C. and stirring was continued at -50° C. for 4 h. The reaction mixture was poured on ice, acidified with 1 N HCl and extracted with ether. After washing with sat. NaHCO3 -sol., brine and drying over MgSO4 the crude product was purified by silica gel column chromatography with hexane/EtOAc 5:1 to give (1 S,2R,3S,5R,6S)-2-azido-3-hydroxy-bicyclo[3.1.0]hexane-2,6-dicarboxylic acid 2-benzyl ester 6-ethyl ester (X-1) (51 mg, 51%) as a colorless oil. 1H-NMR (250 MHz, CDCl3) □1.26 (3H, t, J=7.2 Hz), 2.03-2.18 (3H, m),2.31-2.48 (2H, m),2.53 (1H, t,J=4 Hz),4.13 (2H, q,J=7.2 Hz), 4.21 (1H,bs), 5.26 (2H, s), 7.36-7.40 (5H, m); MS [EI]300 [(M--OEt)+ ];
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