[NH2:1][C:2]1[C:6]([C:7]([OH:9])=[O:8])=[CH:5][NH:4][N:3]=1.[CH:10]1([O:15][C:16]2[CH:17]=[C:18]([CH:21]=[CH:22][C:23]=2[O:24][CH3:25])[CH:19]=O)[CH2:14][CH2:13][CH2:12][CH2:11]1.C([BH3-])#N.[Na+]>CO>[CH:10]1([O:15][C:16]2[CH:17]=[C:18]([CH:21]=[CH:22][C:23]=2[O:24][CH3:25])[CH2:19][NH:1][C:2]2[C:6]([C:7]([OH:9])=[O:8])=[CH:5][NH:4][N:3]=2)[CH2:11][CH2:12][CH2:13][CH2:14]1A suspension of 3-amino-4-pyrazole carboxylic acid (3.56 g, 28 mmol) in 400 ml of methanol and 3-cyclopentyloxy-4-methoxybenzaldehyde (5.06 g, 23 mmol) was stirred at room temperature for 16 hours with sodium cyanoborohydride, 1.85 g (95% pure, 28 mmol). The methanol was evaporated under reduced pressure and the residue was taken up in 100 ml of 15% sodium hydroxide and-extracted twice with 100 ml portions of ether. The aqueous layer was acidified to pH 5 with 5N hydrochloric acid and extracted twice with 100 ml portions of ethyl acetate. The ethyl acetate was dried over sodium sulfate and evaporated. The residue was triturated with ether to give 3.7 g of 3-(3-cyclopentyloxy-4-methoxybenzylamino)-4-pyrazolecarboxylic acid (48.7%). Pure 3-(3-cyclopentyloxy-4-methoxybenzylamino)pyrazole carboxylic acid shows mp. 134-136° C. after crystallization from methanol.
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