Dimethylformamide → (+)-4,5-dihydro-1-[[[(2,2-dimethyl-1-oxopropoxy)methoxy](4-phenylbutyl)phosphinyl]acetyl]-3-phenyl-1H-pyrazole-5-carboxylic acid, phenylmethyl ester

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Reaction Steps

A solution of 4.0 g. of the benzyl ester product from part (c) dissolved in 40 ml. of dry dimethylformamide under argon is treated at ambient temperature with 1.5 g. of chloromethyl pivalate and 1.8 g. of triethylamine. After stirring overnight, the solution is diluted with ethyl acetate and washed with 10% potassium dihydrogen sulfate, water, and saturated brine. The organic solution is dried (MgSO4) and concentrated in vacuo to give the crude product. Flash chromatography on silica gel and elution with ethyl acetate/dichloromethane (1:1) gives homogeneous (+)-4,5-dihydro-1-[[[(2,2-dimethyl-1-oxopropoxy)methoxy](4-phenylbutyl)phosphinyl]acetyl]-3-phenyl-1H-pyrazole-5-carboxylic acid, phenylmethyl ester as an oil.

Provenance & Evidence