Scheme 4.

Synthesis of 1,2,3-Triazol-1-yl Analogues of N⁶-Methyladenosine-5′-N-ethyluronamide 15–19^a

^a Reagents and conditions: (a) KMnO₄, KOH, room temp, 20 h; (b) p-nitrophenol, EDCI, DMF, room temp; (c) ethylamine; (d) 80% TFA/H₂O; (e) CuSO₄·5H₂O, sodium ascorbate, L-proline, Na₂CO₃, NaN₃, H₂O/^tBuOH 1:1, 60 °C; (f) CuSO₄·5H₂O, sodium ascorbate, alkyne, H₂O/^tBuOH 1:1, room temp.