An efficient synthesis of phenyl barbituric-(2-¹⁴C) acid

Barbituric acids are sedative drugs consisting of variety of synthetic substances with closely related chemical structures and similar pharmacological activities. Barbituric acid itself does not possess hypnotic property but when alkyl, aryl or alicyclic groups are introduced into the 5-position, the resultant compounds show marked physiological activity. Barbiturates are prepared by the condensation of urea with malonic acid or its alkylated esters in presence of a slight excess of sodium alkoxide in alcohol. In reported procedures the condensation reaction of phenyl diethyl malonate and urea was carried out in ethyl alcohol and sodium ethoxide but the yield obtained was very low. In general, arylated malonic esters are difficult to prepare than alkylated ones. We carried out reactions in methyl alcohol and sodium methoxide in place of ethyl alcohol and sodium ethoxide. In cold runs, yield of phenyl barbituric acid obtained was consistently more than 70 % and hence employed for the preparation of phenyl barbituric-[2-¹⁴C] acid. Radiolabelled barbituric acid obtained is further used for the preparation of its labelled analogues. (author)