The reaction of ethylene oxide with uridine derivatives in an aqueous solution at room temperature was investigated. 1-Methyluracil gave 1-methyl-3-(2-hydroxyethyl)-uracil (II) quantitatively upon reaction with ethylene oxide at pH 10. The reaction of uridine with ethylene oxide at neutral pH results in the formation of 3-(2-hydroxyethyl)-uridine (IV) quantitatively. These products, II and IV, were isolated as crystals and the structure well defined. The rate of N3-alkylation of uridine increases with the increase of pH value. This indicated that the reaction proceeds through the dissociated form of uridine. At a high-pH region, alkylation of the hydroxyl group(s) of ribose moiety took place concomitantly with the N3-alkylation and gave multiply 2-hydroxyethylated derivatives of uridine. In the reaction of uridine 5'-phosphate with ethylene oxide, besides the N3-hydroxyethylation, phosphodiester formation was also observed. In a high-pH solution, the hydroxyethylation of sugar-hydroxyl group(s) took place as in the case of uridine. Synthesis of uridine 5'-phosphate 2-hydroxyethyl ester by the reaction of uridine 5'-phosphate with ethylene glycol in the presence of dicyclohexyl carbodiimide was described.
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