C([O:3][C:4]([C@@H:6]1[C@@H:11]2[C@H:7]1[CH2:8][C@@H:9]([O:25][CH3:26])[C@@:10]2([N:22]=[N+]=[N-])[C:12]([O:14]CC1C=CC=CC=1)=[O:13])=[O:5])C>CC(O)=O.O.[Pd]>[NH2:22][C@@:10]1([C:12]([OH:14])=[O:13])[C@H:9]([O:25][CH3:26])[CH2:8][C@@H:7]2[C@H:11]1[C@H:6]2[C:4]([OH:5])=[O:3]A solution of (1S,2R,3R,5R,6S)-2-azido-3-methoxy-bicyclo[3.1.0]hexane-2,6-dicarboxylic acid 2-benzyl ester 6-ethyl ester (XXIII-1) (214 mg, 0.56 mmol) in HOAc (8 mL) and H2O (2 mL) was hydrogenated in the presence of Pd/C (35 mg, 10% Pd/C) at 23° C. for 18 h. The catalyst was removed by filtration, the filter cake washed with 50% aqueous acetic acid. After removal of the solvent in vacuum, the beige residue was refluxed in 10% HCl (15 mL) for 4 h. The solution was cooled to 23° C., filtered, washed with water and evaporated to dryness. The remaining pale yellow solid was dissolved in EtOH (10 mL) and propylene oxide (5.6 mL) and refluxed for 15 min, whereupon the amino acid precipiated. After cooling to 23° C., the product was filtered off, washed with ether and dried to give (1S,2R,3R,5R,6S)-2-amino-3-methoxy-bicyclo [3.1.0]hexane-2,6-dicarboxylic acid (I-7) (100 mg 74%) as a white solid. 1H-NMR (250 MHz, D2O) □1.86 (1H, t, J=3.5 Hz), 2.04-2.23 (3H, m), 2.50 (1H, dd, J=12, 7 Hz), 3.29 (3H, s), 3.62 (1H, bt,J=8 Hz); MS[ISN] 214 [(M-H)- ]; mp>250° C.; □D20 -13.84° (c=1.01, H2O).
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