Figure 2. Synthesis of 8-modified nucleoside analogues 2a–g, 3 and 7.

(i) Primary amine, MeOH, 65°C, 24 h or secondary amine, MeOH, room temperature, 24 h; (ii) MeSNa 25%/H₂O, DMF, room temperature, 3 h; (iii) Ac₂O, pyridine, room temperature, 5 h; (iv) KMnO₄, CH₃CO₂H/H₂O (50/50 v/v), 0°C, 1 h; (v) NaCN, DMF, room temperature, 3 h; (vi) NaOH 1 M, H₂O, room temperature, 7 h.