[CH3:1][O:2][C:3]1[CH:4]=[C:5]([CH:26]=[C:27]([O:31][CH3:32])[C:28]=1[O:29][CH3:30])[C:6]([CH2:8][N:9]1[CH2:14][CH2:13][CH:12]([N:15]2[CH2:20][C:19]3[CH:21]=[CH:22][CH:23]=[CH:24][C:18]=3[O:17][C:16]2=[O:25])[CH2:11][CH2:10]1)=[O:7].[BH4-].[Na+]>CO>[CH3:32][O:31][C:27]1[CH:26]=[C:5]([CH:6]([OH:7])[CH2:8][N:9]2[CH2:10][CH2:11][CH:12]([N:15]3[CH2:20][C:19]4[CH:21]=[CH:22][CH:23]=[CH:24][C:18]=4[O:17][C:16]3=[O:25])[CH2:13][CH2:14]2)[CH:4]=[C:3]([O:2][CH3:1])[C:28]=1[O:29][CH3:30]In this example, 2.8 g of 1-(3,4,5-trimethoxybenzoylmethyl)-4-(2-oxo-3,4-dihydro-2H-1,3-benzoxazin-3-yl)-piperidine obtained in the same manner as in Example 7 is mixed with 150 ml of methanol. While this mixture is stirred at 0° to 10° C., 1.5 g of sodium borohydride is added thereto over a period of 2 hours. Then, the mixture is stirred overnight at room temperature. The mixture is further mixed with 1 g of sodium borohydride and stirred overnight. The white crystals deposited are separated by filtration, washed with methanol and water and dried to obtain 1.96 g of a crude product. The crude product is recrystallized from ethanol to obtain 1.76 g of the desired product.
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