[CH2:1]([O:8][C:9]([NH:11][C@H:12]1[CH2:17][CH2:16][CH2:15][C@@H:14]([C:18]([OH:20])=O)[CH2:13]1)=[O:10])[C:2]1[CH:7]=[CH:6][CH:5]=[CH:4][CH:3]=1.[N:21]1C=CC=CC=1.C(OC(OC(C)(C)C)=O)(OC(C)(C)C)=O.C(=O)(O)[O-].[NH4+]>O1CCOCC1>[C:18]([C@@H:14]1[CH2:15][CH2:16][CH2:17][C@H:12]([NH:11][C:9](=[O:10])[O:8][CH2:1][C:2]2[CH:7]=[CH:6][CH:5]=[CH:4][CH:3]=2)[CH2:13]1)(=[O:20])[NH2:21]To a solution of (1R,3S)-3-Benzyloxycarbonylaminocyclohexanecarboxylic acid, 18c, (10.0 g, 36.1 mmol) in 1,4-dioxane (300 mL) was added pyridine (2.9 mL, 36.1 mmol), followed by di-tert-butyl dicarbonate (10.7 mL, 46.9 mmol) and ammonium bicarbonate (10.1 g, 126.2 mmol). After 3 hours, another portion of di-tert-butyl dicarbonate (1.5 g, 6.8 mmol) and ammonium bicarbonate (1.5 g, 6.8 mmol) was added and stirring was continued overnight. The reaction was quenched by addition of 2N HCl (400 mL) and stirred for 1 hour. The resulting suspension was filtered under reduced pressure, washed with 2N HCl (50 mL), water (8×50 mL) and hexanes (3×50 mL) and vacuum dried to provide benzyl N-[(1S,3R)-3-carbamoylcyclohexyl]carbamate, 18d, (9.1 g, 91%) as a white solid.
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