Pyrimidine Nucleosides. III. On the Syntheses of Cytidine and Related Pyrimidine Nucleosides¹

Chemistry of the Nucleotides

“…The general method, first extended to the synthesis of pyrimidine nucleosides by Fox and co-workers (25), has also been applied with considerable success to the synthesis of a number of N3-glycosyl pyrimidines, including 3'-and 5' -amino nucleosides (26) and 5' fiuoro nucleosides (14), in addition to the naturally occurring nucleosides (27). In the main, the rule proposed by Baker an , d stating that in this type of synthesis the stereochemistry of the glycosyl linkage is controlled by the 2-acyloxy group of the sugar, resulting in forma tion of a nucleoside containing a CI_C2 trans configuration regardless of the original configuration at Cl-C2 of the sugar, has been shown to have a wide validity and, indeed, is now used asa proof of configuration.…”

Reactions of Transglycosylation in the Nucleoside Chemistry

“…In the second step, the O-glycoside (18) undergoes transglycosylation to the N 1 -nucleoside (19), a thermodynamic product of glycosylation. Stability of the pyrimidine O-glycosides and the influence of catalysts, solvents, substituents, size of the sugar ring, etc., on the O N migration have been studied in detail [1][2][3][21][22][23][24][25][26][27] and are reviewed by Fox, Hollenberg and Watanabe [6]. Most importantly, the isomerization proceeds via the 1,O 2 -bisribofuranosyl intermediate (20), and compounds of this type have been isolated from reaction mixtures and fully characterized [28,29].…”

“…A reasonable explanation for it has been presented by Vorbrüggen [34,35] for the synthesis of 5-methoxyuridine (Scheme 7). The used as the ribosylation catalyst to form an N 1 --complex (23). The structure of (23) has been deduced from the 13 C NMR study.…”

Molecular Dynamics of Double Stranded Xylo-Nucleic Acid

“…Sugar modified derivatives like cyclonucleosides and arabinonucleosides have also shown biological activity. 13 Similarly, ribonucleosides derived by substituting the 2′-hydroxyl moiety by fluorine, amino, or methoxy groups have also been studied extensively. 14−16 Therapeutic applications of locked nucleic acids designed to mimic RNA have been well documented in the recent years.…”

“…The sugar moiety is the principal causative agent creating the structural and functional diversity of DNA versus RNA, and hence any modifications in the sugar moiety would influence their properties remarkably. Sugar modified derivatives like cyclonucleosides and arabinonucleosides have also shown biological activity . Similarly, ribonucleosides derived by substituting the 2′-hydroxyl moiety by fluorine, amino, or methoxy groups have also been studied extensively. − Therapeutic applications of locked nucleic acids designed to mimic RNA have been well documented in the recent years.…”