An improved method for the synthesis of N1-substituted orotic acid derivatives is reported. The method involves sequential incorporation of nitrogen atoms to the pyrimidine structure from simple starting materials and thus allows the synthesis of N1-substituted orotic acid derivatives with single 15N label at either N-1 or N-3.
Keywords: 1-substituted orotic acid; 1-substituted uracil; 5-bromouracil; Orotic acid; dihydrouracil; orotidine.