[CH:1]1([C:4]([N:6]2[CH2:11][CH2:10][CH:9]([C:12](OCC)=[O:13])[CH2:8][CH2:7]2)=[O:5])[CH2:3][CH2:2]1.[BH4-].[Li+].B(OC)(OC)OC>O1CCCC1.O>[CH:1]1([C:4]([N:6]2[CH2:7][CH2:8][CH:9]([CH2:12][OH:13])[CH2:10][CH2:11]2)=[O:5])[CH2:2][CH2:3]1A solution of 1-(cyclopropylcarbonyl)-4-carboethoxy piperidine (35 g, 156 mmol) in anhydrous tetrahydrofuran (350 mL) was stirred at ambient temperature under a nitrogen atmosphere. A solution of lithium borohydride in tetrahydrofuran (2M, 78 mL, 156 mmol) was added dropwise. Trimethyl borate (1.77 mL, 15.7 mmol) was added, then the reduction mixture was stirred for about 48 hours. Water was added dropwise with vigorous stirring until the vigorous gas evolution ceased. The mixture was diluted twofold with water and extracted three times with ethyl acetate. The combined organic layers were dried over magnesium sulfate, filtered and concentrated in vacuo. Vacuum distillation (bp 165° C., 0.5 mm Hg) gave a clear, colorless liquid (18.2 g): IR (neat): 3410 (br, s), 3094 (w), 3008 (s), 2918 (s), 2858 (s), 1738 (m), 1613 (s), 1448 (s), 1375 (s), 1316 (s); 1H-NMR: 4.7-4.5 (m, 1H), 4.4-4.1 (m, 1H), 3.6-3.4 (m, 2H), 3.2-2.5 (m, 3H), 2.0-1.7 (m, 4H), 1.4-1.1 (m, 1H), 1.0-0.8 (m, 2H), 0.8-0.65 (m, 2H); HRMS: Calcd for C10H17NO2 :183.1259; Found: 183.1250; Anal.: Calcd for C10H17NO2 :C, 65.54, H, 9.35, N, 7.64; Found: C, 65.83, H, 9.43, N, 7.50.
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