To a solution of 5′-amino-2′,3′-isopropylidene adenosine (280 mg, 0.92 mmol, 1.00 eq) in anhydrous DMF (4.6 mL) was added Et3N (250 μL, 1.83 mmol, 2.00 eq). 2-nitro-4-trifluoromethylbenzenesufonyl chloride (396 mg, 1.37 mmol, 1.50 eq) was added at 0 °C and the reaction mixture was stirred for 4 h at room temperature under argon. The reaction mixture was diluted with AcOEt (30 mL) and water (30 mL). The aqueous layer was extracted with AcOEt (3 × 30 mL) and the combined organic extracts were washed with brine (30 mL), dried over Na2SO4 and concentrated under vacuum. The residue was purified by flash column chromatography (silica gel, linear gradient 0–5% MeOH in DCM) to give 28 (230 mg, 45%) as a dark red solid. Rf 0.34 (8:92 MeOH/CH2Cl2). 1H NMR (500 MHz, DMSO‑d 6) δ 8.93 (t, J = 5.1 Hz, 1H), 8.50 (d, J = 1.8 Hz, 1H), 8.28 (s, 1H), 8.14 (s, 1H), 8.10 (dd, J = 1.6 Hz, J = 8.6 Hz, 1H), 8.04 (d, J = 8.3 Hz), 7.45 (br. s, 2H), 6.11 (d, J = 2.9 Hz, 1H), 5.34 (dd, J = 6.3 Hz, J = 2.9 Hz, 1H), 4.92 (dd, J = 6.3 Hz, J = 3.1 Hz, 1H), 4.20 (td, J = 5.9 Hz, J = 3.1 Hz, 1H), 3.37–3.25 (m, 2H), 1.50 (s, 3H), 1.27 (s, 3H). 13C NMR (125 MHz, DMSO‑d 6) δ 156.1, 152.4, 148.4, 147.6, 140.2, 136.4, 133.8, 133.5, 133.2, 133.0, 130.8, 129.4, 125.5, 123.4, 121.2, 119.0, 122.0, 122.0, 119.3, 113.5, 107.7, 89.4, 84.3, 83.0, 81.5, 44.7, 26.9, 25.0. HRMS (ESI+): m/z calcd for C20H21N7O7SF3 [M+H]+: 560.1175, Found 560.1180.