A method for the synthesis of 5-carboxymethylaminomethyl-2- seleno- and 5-carboxymethylaminomthyl-2-thiouracil was developed. This method involved the condensation of selenourea with the enolate of ethyl alpha-formyl-N- carboxymethylaminopropionate which was generated in situ from ethyl N-carboxymethylaminpropionate.
