Abstract
Treatment of 4-amino-2-methylthiopyimidine with 2, 3, 5-tri-O-benzoyl-D-ribosyl chloride afforded the ribosylpyrimidinium chloride (VI), which, on treatment with hydrogen sulfide, gave 2', 3', 5'-tri-O-benzoyl-2-thiocytidine (VII) and 2-thiocytidine (VIII) by further de-benzoylation. Methylation of VIII afforded 2-methylthiopyrimidinium derivative (IX). Treatment of IX (or VI) with methanolic ammonia gave 2, 4-diamino-1-(β-D-ribofuranosyl)-pyrimidinium salt. With alkali IX (or VI) gave cytidine. This condensation can be regarded as an extended Hilbert-Johnson procedure for pyrimidine nucleoside synthesis. Relationships between stability of ribosylpyrimidinium salts and structure of their pyrimidines are discussed. The mechanism of the Hilbert-Johnson reaction was established therefrom.
