N-{[(4R,6R)-6-(6-amino-9H-purin-9-yl)-2,2-dimethyl-tetrahydro-2H-furo[3,4-d] [1,3]dioxol-4-yl]methyl}-N-(2-{[(2R,5R)-2-(6-amino-9H-purin-9-yl)-4-[(tert-butyldimethylsilyl)oxy]-5-{[(tert-butyldimethylsilyl)oxy]methyl}oxolan-3-yl]oxy}ethyl)-4-nitrobenzene-1-sulfonamide (19)
Following method B using 18 (290 mg, 0.59 mmol, 1.00 eq), 19 (450 mg, 74%) was obtained as a pale yellow solid. Rf 0.60 (10:90 MeOH/DCM). 1H NMR (600 MHz, CDCl3) δ 8.30 (2s, 2H), 8.14 (s, 1H), 8.03–7.98 (m, 2H), 7.74 (s, 1H), 7.70–7.66