C[O:2][C:3](=O)[C@H:4]([CH:30]([CH3:32])[CH3:31])[N:5]([C:24](=[O:29])[CH2:25][CH2:26][CH2:27][CH3:28])[CH2:6][C:7]1[CH:12]=[CH:11][C:10]([C:13]2[CH:18]=[CH:17][CH:16]=[CH:15][C:14]=2[C:19]2[NH:23][N:22]=[N:21][N:20]=2)=[CH:9][CH:8]=1.[BH4-].[Li+]>C1COCC1>[OH:2][CH2:3][C@@H:4]([N:5]([C:24](=[O:29])[CH2:25][CH2:26][CH2:27][CH3:28])[CH2:6][C:7]1[CH:8]=[CH:9][C:10]([C:13]2[CH:18]=[CH:17][CH:16]=[CH:15][C:14]=2[C:19]2[NH:23][N:22]=[N:21][N:20]=2)=[CH:11][CH:12]=1)[CH:30]([CH3:32])[CH3:31]0.8 g of N-valeryl-N-[(2'-(1H-tetrazol-5-yl)biphenyl-4-yl)methyl]-(L)-valine methyl ester is dissolved in 30 ml of THF, treated at 5° C. with 83 mg of lithium borohydride and stirred at room temperature for 24 h. The reaction mixture is then concentrated, treated with water and adjusted to pH 2 with hydrochloric acid, a white precipitate forming. The mixture is extracted with ethyl acetate, washed with water and brine, dried and finally separated by means of flash chromatography (CH2Cl2 -MeOH 5:1). FAB-MS: m/e=422 (M+H)+.
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