[BH4-].[Na+].[CH2:3]([C:7]1[N:8]([CH2:15][C:16]2[CH:21]=[CH:20][C:19]([CH:22]([CH:26]3[CH2:30][CH2:29][CH2:28][CH2:27]3)[C:23]([OH:25])=[O:24])=[CH:18][CH:17]=2)[C:9]([CH:13]=[O:14])=[C:10]([Cl:12])[N:11]=1)[CH2:4][CH2:5][CH3:6].Cl>C(O)C>[CH2:3]([C:7]1[N:8]([CH2:15][C:16]2[CH:17]=[CH:18][C:19]([CH:22]([CH:26]3[CH2:27][CH2:28][CH2:29][CH2:30]3)[C:23]([OH:25])=[O:24])=[CH:20][CH:21]=2)[C:9]([CH2:13][OH:14])=[C:10]([Cl:12])[N:11]=1)[CH2:4][CH2:5][CH3:6]0.1 g (2.9 mmol) of sodium borohydride is added to 1.5 g (2.9 mmol) of the compound from Example V in 25 ml of ethanol. After 1 h at room temperature, the reaction mixture is acidified (pH 4) with 2N HCl and extracted three times with CH2Cl2. The organic phase is dried over Na2SO4 and concentrated, and the product is crystallised from ethyl acetate/petroleum ether. A 1:1 mixture of the diastereomers is obtained.
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