Synthesis of some monocyclic-N-acetyl 4′-aza-D-nucleosides

1,2,3,5‐Tetra‐O‐acetyl‐4‐deoxy‐4‐(acetamido)‐β‐D‐ribofuranose 5 was prepared from L‐lyxose, which on condensation with silylated nucleoside bases gave the corresponding protected 4′‐azanucleosides. The protecting groups were removed using methanolic ammonia to afford the N‐acetyl‐4′‐azanucleosides, wherein the sugar ring oxygen is replaced with a substituted nitrogen atom, in good yields. Further, the 1‐(4‐deoxy‐4‐acetamido‐β‐D‐ribofuranosyl)thymine 16 was transformed to the corresponding 2′‐deoxy, 2′,3′‐dideoxy derivatives. The stereochemical assignments of the synthesized nucleosides were established based on NMR and X‐ray studies.