Tetrabutylammonium Fluoride → (s)-Di-tert-butyl 4-(3-(2,3-difluorobenzyl)-1-methylureido)-5-hydroxypentyl phosphate

To a solution of (S)-di-tert-butyl 5-(tert-butyldimethylsilyloxy)-4-(3-(2,3-difluorobenzyl)-1-methylureido)pentyl phosphate (4.1 g, 7.95 mmol) in THF (40 mL) was added TBAF (1.0 M in THF, 8.0 mL, 8.0 mmol). The resulting solution was stirred at RT for 1 h. The mixture was quenched with sat. NH4Cl and diluted with EtOAc. The organic layer was washed with sat. NH4Cl (×2) and brine, dried over Na2SO4, filtered, and concentrated under reduced pressure. The residue was purified on silica gel column using a mixture of EtOAc and hexanes to give (S)-di-tert-butyl 4-(3-(2,3-difluorobenzyl)-1-methylureido)-5-hydroxypentyl phosphate (2.52 g, 61%) as a colorless oil. LRMS (M+H+−2 tBu) m/z 383.0.