Scheme 1. Synthesis of boronated nucleoside analogues. Conditions: (a) triphosgene, Na₂CO₃, toluene, rt; (b) imidazole, toluene, rt, 87% over 2 steps; (c) Et₃OBF₄, DCM, rt; (d) 1, DBU, MeCN, rt, 98%; (e) TBAF, THF, 0 °C, 72%; (f) 1, DIAD, PPh₃, 1,4-dioxane, rt, then TBAF, 10%; (g) 2, DCM, 0 °C to rt, 91%; (h) TASF, DMF, 0 °C, 62%; (i) 2, DCM, 0 °C to rt, 92%; (j) HF-pyridine, 60 °C, 52%.