3.3 Grams of 3,4-dimethoxybenzoic acid was dissolved in 30 ml of dimethylformamide, then 2.4 g of triethylamine was added to this solution. Under ice-cooled condition, to this solution was added dropwise 2.75 g of isobutyl chloroformate with stirring, and further stirred for 30 minutes. Then to this reaction mixture was added dropwise a DMF solution containing 5.8 g of o-methoxycarbonyl-α-(1-piperazinyl)acetanilide and stirred for 5 hours. The reaction mixture was concentrated to dryness and subjected to extraction by adding chloroform and 1 N-sodium hydroxide. The chloroform layer was washed with water, dried and removed by distillation, the residue obtained was crystallized by adding ethyl acetate and the crystals formed were collected by filtration. Recrystallized from ethanol to obtain 2.3 g of o-methoxycarbonyl-α-[4-(3,4-dimethoxybenzoyl)-1-piperazinyl]acetanilide in the form of colorless needle-like crystals. Melting point: 167.5°-169.0° C.
