[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+]=[N-])[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].[N-]=[N+]=[N-].[Na+].[BH4-].[Na+].CCOCC>CO.C(Cl)(Cl)Cl.CC(C)=O.O.Cl[Ni]Cl>[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([NH2:22])[C:12]([O:14][CH2:15][C:16]1[CH:17]=[CH:18][CH:19]=[CH:20][CH:21]=1)=[O:13])=[O:5])[CH3:2]
To a solution of (1S,2R,3R,5R,6S)-2-azido-3-hydroxy-bicyclo[3.1.0]hexane-2,6-dicarboxylic acid 2-benzyl ester 6-ethyl ester (VII-1) (200 mg, 0.58 mmol) in MeOH (5.8 mL) and a few drops of chloroform at 0° C. was added NiCl2.6 H2O (661 mg, 2.78 mmol) was dissolved in acetone (45 mL) and H2O (4.5 mL), NaN3 (720 mg, 11.1 mmol) and stirred for 10 min at 0° C. Upon cautious addition of NaBH4 (175 mg, 4.62 mmol) the reaction mixture turned immediately black, stirring was continued at 0° C. for 10 min and then hydrolyzed with water and ether. After additional stirring for 10 min at 0° C., the reaction mixture was extracted with ether, washed with brine (2×50 mL) and dried over Na2SO4 and filtered through celite. The solvent was removed under vacuum, the residue was purified by silica gel column chromatography with ethyl acetate/MeOH 95:5 (+0.6% Et3N) to give (1S,2R,3R,5R,6S)-2-amino-3-hydroxy-bicyclo[3.1.0]hexane-2,6-dicarboxylic acid 2-benzyl ester 6-ethyl ester (VIII) (106 mg, 57%) as a yellow oil. 1H-NMR (250 MHz, CDCl3) □1.25 (3H, t, J=7.1 Hz), 1.75 (1H, t,J=3.5 Hz), 1.97 (1H, m), 2.12 (1H, dd,J=7, 3.5 Hz), 2.14-2.28 (4H, m), 2.33 (1H, dd,J=12.5, 7 Hz), 3.65 (1H, dd, J=8, 7 Hz), 4.10 (2H, q, J=7.1 Hz), 5.22 (1H, d, J=12.5 Hz), 5.27 (1H, d, J=12.5 Hz), 7.38 (5H, m); MS[ISP] 320 (M+H+); □D20 -0.56° (c=0.89, CHCl3).
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