Scheme 2. Synthesis of 2′-OCF₃ adenosine building block A7. Reaction conditions: (a) 1.1 equiv. TIPDSCl₂, in pyridine, room temperature, 5 h, 95%; (b) 1.2 equiv. ^tBuLi, 9.0 equiv. CS₂, 3.0 equiv. CH₃I, in THF, −75 °C to room temperature, 18 h, 74%; (c) 2.5 equiv. benzoylchloride, 6 equiv. NH₃, in pyridine, room temperature, 16 h, 89%; (d) 5.0 equiv. NBS, in HF pyridine and CH₂Cl₂, –75 °C to 0 °C, 3 h, 26%; (e) 1.5 equiv. DMTCl, 0.5 equiv. DMAP, in pyridine, room temperature, 16 h, 88%; (f) 2.5 equiv. 2-cyanoethyl N,N-diisopropylchlorophosphoramidite, 7.5 equiv. iPr₂NEt, 0.5 equiv. 1-methylimidazole, in CH₂Cl₂, room temperature, 2 h, 82%.