Hydrogen Peroxide → (S)-(9H-fluoren-9-yl)methyl (2-((di-tert-butoxyphosphoryl)oxy)-1-(3-fluoro-5-iodophenyl)ethyl)carbamate

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To (S)-(9H-fluoren-9-yl)methyl (1-(3-fluoro-5-iodophenyl)-2-hydroxyethyl)carbamate (5260 mg, 10.45 mmol) was added imidazole (818 mg, 12.02 mmol), imidazole HCl (1857 mg, 17.77 mmol), and DMF (Volume: 50 mL). The reaction was stirred to dissolve under argon for 2-3 minutes. Then di-tert-butyl diisopropylphosphoramidite (4928 mg, 17.77 mmol) was added drop wise over 2-3 minutes and stirred at room temperature for 2 hours. The reaction was followed by neutral LCMS and by TLC eluting with 1:1 ethyl acetate/heptane. The crude reaction was placed in a water bath, hydrogen peroxide 30% (5.34 mL, 52.3 mmol) was added slowly, and the mixture was stirred at room temperature for 30 minutes, followed by LCMS. The crude reaction was placed in an ice bath and excess saturated sodium thiosulphate was added (carefully) drop wise over 5-10 minutes. To the crude reaction mixture was added 800 ml of ethyl acetate washed with water (3×), saturated salt solution, dried sodium sulfate, filtered and concentrated to residue. The crude was purified by silica gel chromatography using 300 g column eluting from 0-55% ethyl acetate in heptane. The desired peak was concentrated to constant mass to give 6560 mg of the desired product as free base used as is, (86% yield). LCMS (m/z): 696.3 (MH+) weak, 1.25 min. Note: −112 fragment at 584.2 is major ion in LCMS as expected from loss of two t-butyl protecting groups. 1H NMR (<cd3od>) d: 7.79 (d, J=7.3 Hz, 2H), 7.64 (d, J=7.3 Hz, 2H), 7.58 (s, 1H), 7.45 (d, J=7.6 Hz, 1H), 7.34-7.42 (m, 2H), 7.22-7.32 (m, 2H), 7.12 (d, J=9.1 Hz, 1H), 4.90 (t, J=6.0 Hz, 1H), 4.41-4.48 (m, 1H), 4.31-4.40 (m, 1H), 4.21 (t, J=6.6 Hz, 1H), 4.08 (t, J=6.3 Hz, 2H), 1.42 (s, 9H), 1.40 (s, 9H).

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