[Cl:1][C:2]1[CH:7]=[C:6]([Cl:8])[CH:5]=[CH:4][C:3]=1[CH:9]([CH2:21][C:22]#[CH:23])[C:10]([OH:20])([C:14]1[CH:15]=[N:16][CH:17]=[CH:18][CH:19]=1)[C:11](=[O:13])[CH3:12].[BH4-].[Na+]>C(O)C>[Cl:1][C:2]1[CH:7]=[C:6]([Cl:8])[CH:5]=[CH:4][C:3]=1[CH:9]([CH2:21][C:22]#[CH:23])[C:10]([C:14]1[CH:15]=[N:16][CH:17]=[CH:18][CH:19]=1)([OH:20])[CH:11]([OH:13])[CH3:12]A solution of 5.8 g of 4-(2,4-dichlorophenyl)-3-hydroxy-3-(3-pyridyl)-6-heptyn-2-one (see Example 4, 1st end product) in 100 ml of ethanol is treated at room temperature with 0.8 g of sodium borohydride and the mixture is stirred for 30 minutes. Thereafter, the excess sodium borohydride is destroyed by adjusting the yellowish reaction solution to pH 1 with 2N sulphuric acid and the mixture is again neutralized with saturated aqueous sodium bicarbonate solution. The mixture is evaporated under reduced pressure in order to remove the solvent, the residue is partitioned between ethyl acetate and water and the organic phase is washed with saturated aqueous sodium chloride solution and evaporated under reduced pressure in order to remove the solvent. The residue is purified by chromatography on silica gel with methylene chloride/ethyl acetate (3:7). In this manner there are obtained 5.7 g of 4-(2,4-dichlorophenyl)-3-(3-pyridyl)-6-heptyne-2,3-diol as a colorless solid foam. In an analogous manner, starting from
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