[NH2:1][CH2:2][C@H:3]1[CH2:8][CH2:7][C@H:6]([C:9]([OH:11])=[O:10])[CH2:5][CH2:4]1.Cl[C:13]([O:15][CH2:16][C:17]1[CH:22]=[CH:21][CH:20]=[CH:19][CH:18]=1)=[O:14]>[OH-].[Na+].O>[C:17]1([CH2:16][O:15][C:13]([NH:1][CH2:2][CH:3]2[CH2:4][CH2:5][CH:6]([C:9]([OH:11])=[O:10])[CH2:7][CH2:8]2)=[O:14])[CH:22]=[CH:21][CH:20]=[CH:19][CH:18]=1To a solution of trans-4-(aminomethyl)cyclohexanecarboxylic acid (10 g, 63.6 mmol, Aldrich) in 2N aqueous NaOH (65 ml) at 0° C. was added benzyl chloroformate (11.9 g, 70 mmol, Aldrich) and the reaction temperature was maintained below 10° C. The cloudy mixture was stirred at RT for 0.5 h. It was then diluted with H2O (100 ml). The clear solution was washed with ether (3×80 ml). The pH of the aqueous layer was adjusted to 2 by adding 6N HCl. The precipitates were filtered and dried in vacuo. 17.8 g of 23 was obtained as a white solid.
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