A solution of 10 g. of [hydroxy(4-phenylbutyl)phosphinyl]acetic acid, from part (b), in 40 ml. of dry dichloromethane containing 0.2 ml. of dimethylformamide is heated to reflux temperature. Thionyl chloride (5.1 g.) is added dropwise while maintaining the temperature at reflux. After an additional 30 minutes heating, the solution is cooled to 5° and a solution of 11.6 g. of (+)-4,5-dihydro-3-phenyl-1H-pyrazole-5-carboxylic acid, phenylmethyl ester, hydrochloride (1:1), from part (a), in 50 ml. of dichloromethane is added at once, followed by dropwise addition of 11.9 g. of triethylamine while the temperature is maintained at 5°-10° with cooling. After stirring overnight at ambient temperature, the mixture is washed three times with aqueous hydrochloric acid (1.5 N) and three times with water. The organic solution is dried (MgSO4) and concentrated in vacuo to give (+)-4,5-dihydro-1-[[hydroxy(4-phenylbutyl)phosphinyl]acetyl]-3-phenyl-1H-pyrazole-5-carboxylic acid, phenylmethyl ester which can be crystallized from acetone.
