The Collaborative International Dictionary of English v.0.48:

malonylurea \malonylurea\ n.
   A white crystalline acid derived from pyrimidine; it is used
   in preparing barbiturate drugs.

   Syn: barbituric acid.
        [WordNet 1.5]

WordNet (r) 3.0 (2006):

malonylurea
    n 1: a white crystalline acid derived from pyrimidine; used in
         preparing barbiturate drugs [syn: barbituric acid,
         malonylurea]