A new and convenient synthetic route to formylglycineamide ribonucleotide, an intermediate in the pathway of purine ribonucleotide biosynthesis de novo, is described. The method utilizes direct phosphorylation of the 5′-position of the linear riboside without protection of the 2′,3′-hydroxyl groups of the ribose, and gives a good yield of mixed α and β anomers. This route is suitable for synthesis of the natural product in quantities required for biological studies.