Identification of the major degradation product of 1-propyl-3,5-diethyl-6-chlorouracil in rabbits and mechanism of the formation of bicyclic barbituric acid metabolites.

The major degradation product of 1-propyl-3,5-diethyl-6-chlorouracil in rabbits is identified as 6,8-diethyl-2-methyl-tetrahydrooxazolo[3,2-c]pyrimidine-5,7(4H,6H)-dione. The mechanism of the formation of this bicyclic barbituric acid derivative is discussed. The biotransformation takes place via substitution of the chlorine by beta- and not by alpha-hydroxy group of the intermediate hydroxypropane.