Thiosugars. XII. Synthesis of New 3′‐<i>O</i>‐Substituted 2′,5′‐Anhydro‐2′‐thio‐α‐<scp>d</scp>‐pentofuranosyl Nucleoside Analogues

Methyl 2,5-anhydro-3-O-(2-methoxyethyl)-2-thio-beta-D-arabinofuranoside and methyl 2,5-anhydro-3-O-(2-fluorobenzyl)-2-thio-alpha-D-lyxofuranoside were transformed into the corresponding uridine, thymidine, cytidine and adenosine analogues, which exclusively exhibited the alpha-configuration irrespective of the anomeric configuration of the donor. The structure, configuration, and conformation of the products was elucidated by X-ray structure analyses. The nucleoside analogues were tested for antiviral activities.