To a solution of 3′,5′-diacetyl-5-iodo-2′-deoxyuridine (219 g, 5.00 mmol) acetonitrile (ACN, 75 ml), triethylamine (TEA, 6.96 ml, 50.0 mmol) and DMAP (0.15 g, 1.25 mmol) was added mesitylsulfonyl chloride (2.19 g, 10.0 mmol). After stirring at ambient temperature for 18 h, DBU (2.14 ml, 10.0 mmol) and 2-aminothiophenol was added (2.14 g, 20.0 mmol) and the solution was stirred for 1 h. The reaction mixture was concentrated and the crude product was partitioned between ethyl acetate (EA, 200 ml) and saturated aqueous sodium bicarbonate (SASB, 200 ml). The organic layer was dried (Na2SO4) and concentrated on the rotary evaporator. The crude product was purified by flash chromatography on silica gel [1-5% 2-propanol/dichloromethane (DCM)] to deliver the product 1H NMR (CDCl3) δ 2.10 (s, 3H), 2.15 (m; 1H, 2.17 (s, 3H, 2.77 (ddd, 1H, J=2.2, 5.2, 15.1 Hz), 4.14 (bs, 1H), 4.35 (m, 3H), 5.20 (m, 1H), 6.13 (t, 1H, J=65 Hz), 6.78 (m, 2H), 7.30 (m 2), 8.05 (s, 1H).
