Imidazole → (2S,3R)-2-tert-Butoxycarbonylamino-3-(tert-butyl-diphenyl-silanyloxy)-butyric acid methyl ester

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Reaction Steps

(2S,3R)-2-tert-Butoxycarbonylamino-3-hydroxy-butyric acid methyl ester (1.85 g, 7.93 mmol) was dissolved in N,N-dimethylformamide (10 mL), under an atmosphere of nitrogen. tert-Butyl(chloro)diphenylsilane (2.89 mL, 11.1 mmol) was added followed by imidazole (1.08 g, 15.9 mmol) and the reaction was left to stir for 72 h. The reaction mixture was diluted with water and then extracted with ethyl acetate. The combined organics were dried over anhydrous sodium sulfate, filtered and concentrated. The residue was purified by silica gel chromatography using a stepwise gradient iso-hexanes/ethyl acetate from 1:0 to 4:1 to afford the title compound (3.56 g, 95%) as a pale Greene oil. 1H NMR (300 MHz, CDCl3) δ 0.89 (d, J=6.6 Hz, 3H), 1.04 (s, 9H), 1.10 (s, 9H), 3.64 (s, 3H), 4.18-4.26 (m, 1H), 4.39-4.50 (m, 1H), 5.34 (d, J=9.9 Hz, 1H), 7.36-7.50 (m, 6H), 7.60-7.69 (m, 2H), 7.71-7.77 (m, 2H). LCMS (m/z) 472.2 [M+H], Tr=4.13 min.

Provenance & Evidence