2,4,6-Triisopropylbenzenesulfonyl azide → (4S)-3-[(2S)-2-azido-3-methyl-3-phenylbutanoyl]-4-benzyl-1,3-oxazolidin-2-one

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Reaction Steps

A solution of (4S)-4-benzyl-3-(3-methyl-3-phenylbutanoyl)-1,3-oxazolidin-2-one (1.0 g, 3.0 mmol, from Reference Example 26) in anhydrous tetrahydrofuran (16 mL) is cooled to −78° C. in a dry-ice/acetone bath while stirring under a nitrogen atmosphere. Potassium hexamethylsilazide (0.5 M solution in toluene, 6.6 mL, 3.3 mmol) is added dropwise to the solution via syringe. After stirring for 1 hour at −78° C., trisyl azide (1.2 g, 3.8 mmol) in tetrahydrofuran (8 mL) is added dropwise. The reaction mixture is stirred for 2-3 minutes at −78° C. and then quenched by the addition of glacial acetic acid (0.8 mL). Stirring is continued for 1 hour at 40° C. The reaction mixture is diluted with brine and diethyl ether. The aqueous phase is extracted thrice with diethyl ether. The combined extracts are washed with saturated aqueous sodium hydrogen carbonate and saturated aqueous sodium chloride, dried over sodium sulfate, decanted, and concentrated under reduced pressure to afford a white/yellow solid. The crude material is purified by flash chromatography (ethyl acetate/hexanes) to afford a clear, straw colored oil (1.1 g, 79%). TOF MS (ES+): (M+H)=379.2

Provenance & Evidence