The general procedure for the synthesis of 4-amino-1-((2R,4S,5R)-4-hydroxy-5-(hydroxymethyl)tetrahydrofuran-2-yl)-5-methylpyrimidin-2,4(1H,3H)-diones, using 1-((2R,4S,5R)-4-hydroxy-5-(hydroxymethyl)tetrahydrofuran-2-yl)-5-methylpyrimidin-2(1H)-one as a starting material was carried out as follows. DMF a nucleoside solution was prepared (substrate concentration of 0.3 M, except for compounds 3 and 4, which was 0.05 M) to which PyAOP (1.6 eq.) and DBU (1.6 eq.) were added. The reaction mixture was stirred at 20 °C for 1 min. Subsequently, N-nucleophilic reagent (4 eq. dissolved in THF if 1a was used, or concentrated NH4OH, 10 eq.) was added to the reaction system. The reaction continued to be stirred at 20 °C for 5 min to 4 h and the progress of the reaction was monitored by TLC. Upon completion of the reaction, the solution was concentrated under vacuum. Separation by fast column chromatography on silica gel afforded purified forms of the target product 5MedC and its oxidized derivatives 1'-20'.
