First synthesis of the main metabolite of secobarbital

The main metabolites of barbituric acids, bearing an alkyl side chain and a n unsaturated side chain, e.g. allyl or phenyl, are often omega-carboxyalky l barbituric acids still possessing the unsaturated side chain. The synthes is of these metabolites which are quite useful for immune assay techniques, is not possible by standard literature procedures. We were able to synthes ize the main metabolite of secobarbital for the first time using guanidine instead of urea or thiourea for the ring closure. Guanidine is advantageous for this condensation because elevated temperatures or prolonged reaction times were avoided. The resulting products are easily transformed into the desired compounds.