Abstract: This invention relates to a process for preparation of pyrimidinetriones. It also relates to novel N-dihydroxyphosphoryl pyrimidinetrione derivatives which may be useful as water-soluble prodrugs of certain pyrimidinetrione compounds.

Abstract: A process for the preparation of pyrimidinetrione derivatives of formula (I) is described ##STR1## wherein R.sup.1 and R.sup.2, which may be the same or different, represent aliphatic, araliphatic or aryl groups, and R.sup.3 represents a group of the formula --CH.sub.2 CH(OCONH.sub.2)--CH.sub.2 OX wherein X is hydrogen or a C.sub.1-5 alkyl group which comprises reacting approximately equimolar amounts of a monoalkali metal salt of a compound of formula (I), wherein R.sup.3 is a hydrogen atom, with an alkylating agent R.sup.3 Hal wherein R.sup.3 is as defined above and Hal represents a halogen atom, in the presence of at least 0.2 moles of an acid of formula (I) wherein R.sup.3 is a hydrogen atom per mole of alkali metal salt. The yield is increased by up to 50% by this method. The process is of particular application to the preparation of febarbamate, 1-(3-.sup.n butoxy-2-carbamoyloxypropyl)-5-ethyl-5-phenyl-(1H, 3H,5H)pyrimidine-2,4,6-trione.