m-Chloroperbenzoic acid → Benzyl 2-(di-tert-butoxyphosphoryloxy)ethyl(ethyl)carbamate

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Reaction Steps

A solution of benzyl ethyl(2-hydroxyethyl)carbamate (INTERMEDIATE 47, 1.0 g, 4.48 mmol) and di-tert-butyl diethylphosphoramidite (4.47 ml, 16.1 mmol) in THF (146 ml) was treated with tetrazole (1.57 g, 22.39 mmol) in one portion. The resulting mixture was stirred at r.t for 50 minutes and the clear solution became cloudy. The mixture was cooled using an acetone/dry ice bath (˜−77° C.) and m-CPBA (6.96 g) was added over the course of ˜1 minute. The mixture was stirred under these conditions for 20 minutes and subsequently allowed to warm to r.t. over 10 minutes. Sodium bisulfite (aq., 10% w/v, 3.41 ml) was added and the mixture was stirred for 10 minutes, concentrated in vacuo, diluted with EtOAc (200 ml), and washed with sodium bisulfite (aq., 100 ml), and NaHCO3 (aq., 5% w/v, 100 ml). The organic layer was dried (Na2SO4), filtered, and evaporated under reduced pressure. The concentrate was purified by column chromatography (ISCO, silica gel column, eluting with 0→100% EtOAc in hexanes) to give the title compound (1.1 g, yield: 60%).

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