Transfer RNA components. I. Direct synthesis of nucleosides of cytosine and 2-thiocytosine.

The direct synthesis of cytosine nucleosides results from the reaction of cytosine or N-acetylcytosine with a glycosyl halide in the presence of mercury(II) cyanide. The nature of the products varies with the solvent and the presence or absence of molecular sieve. With acetobromoglucose in toluene, cytosine gives a mixture of the N(1),N(3),N(6)-triglucoside (VI) and the O(2)-glucoside (V). In nitromethane, cytosine, N-acetylcytosine, and 2-thiocytosine give satisfactory yields of the corresponding N(3)-glycosides. A convenient synthesis and purification of 2′,3′,5′-tri-O-acetyl-2-thiocytidine (XI) is described.