C(O[BH-](OC(=O)C)OC(=O)C)(=O)C.[Na+].[C:15]([O:19][C:20]([N:22]1[CH2:27][CH2:26][CH:25]([NH:28][CH2:29][CH2:30][CH:31]([CH3:33])[CH3:32])[CH2:24][CH2:23]1)=[O:21])([CH3:18])([CH3:17])[CH3:16].[S:34]1[CH:38]=[CH:37][N:36]=[C:35]1[CH:39]=O.ClCCl>C(OCC)(=O)C>[C:15]([O:19][C:20]([N:22]1[CH2:23][CH2:24][CH:25]([N:28]([CH2:29][CH2:30][CH:31]([CH3:33])[CH3:32])[CH2:39][C:35]2[S:34][CH:38]=[CH:37][N:36]=2)[CH2:26][CH2:27]1)=[O:21])([CH3:18])([CH3:17])[CH3:16]Sodium triacetoxyborohydride (0:30 g, 1.42 mmol) is added to a stirred solution of 4-(3-methyl-butylamino)-piperidine-1-carboxylic acid tert-butyl ester (0.19 g, 0.71 mmol), 2-thiazolecarboxaldehyde (0.12 ml, 1.42 mmol), and dichloromethane (3.5 ml). The reaction is stirred overnight at room temperature under nitrogen. The reaction is diluted with ethyl acetate, washed with aqueous saturated NaHCO3, dried over Na2SO4, filtered, and concentrated. Water is added to the residue, and the solution loaded onto a SCX-2 (10 g) column and washed with water (20 ml) and methanol (20 ml). The product is then eluted with 2M ammonia in methanol (30 ml). The filtrate is concentrated and the crude material purified on silica gel eluting with 0-50% ethyl acetate/hexanes to yield (0.20 g) of 4-{(3-methyl-butyl)-[(thiazol-2-yl)-methyl]-amino}-piperidine-1-carboxylic acid tert-butyl ester: mass spectrum (ion spray): m/z=368 (M+1); 1H NMR (CDCl3): δ=7.67 (1H, d), 7.23 (1H, d), 4.17 (2H, brs), 3.93 (2H, s), 2.72-2.54 (5H, m), 1.78 (2H, brd), 1.7-1.57 (2H, m), 1.45-1.41 (10H, m), 1.40-1.32 (2H, m), 0.87 (6H, d).
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