Diisopropylethylamine → (2S,3S,4S)-4-fluoro-2-(2-fluoro-3-trifluoromethoxy-phenylcarbamoyl)-3-methoxy-pyrrolidine-1-carboxylic acid tert-butyl ester

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Reaction Steps

To a solution of (2S,3S,4S)-4-fluoro-3-methoxy-pyrrolidine-1,2-dicarboxylic acid 1-tert-butyl ester and (2R,3R,4R)-3-fluoro-4-methoxy-pyrrolidine-1,2-dicarboxylic acid 1-tert-butyl ester (prepared as described in Scheme B25, 1.00 g, 3.80 mmol) in CH2Cl2 (10 mL) at 0° C. under nitrogen atmosphere was added 1-chloro-N,N,2-trimethylprop-1-en-1-amine (609 mg, 4.56 mmol) and the mixture was stirred at this temperature for 1 h. 2-Fluoro-3-(trifluoromethoxy)aniline (0.815 mg, 4.18 mmol) was then added, followed by DIPEA (1.327 mL, 7.60 mmol) and the mixture was stirred at RT for 1 h. The crude residue was purified by flash column chromatography on silica gel (c-hexane/EtOAc 1:0 to 1:1) to give (2S,3S,4S)-4-fluoro-2-(2-fluoro-3-trifluoromethoxy-phenylcarbamoyl)-3-methoxy-pyrrolidine-1-carboxylic acid tert-butyl ester. 1H NMR (400 MHz, DMSO-d6) 2:1 mixture of rotamers δ (ppm): 10.15 (m, 1H), 7.87 (m, 1/3H), 7.77 (m, 2/3H), 7.31 (m, 2H), 5.29-5.11 (m, 1H), 4.76 (d, 1/3H), 4.70 (d, 2/3H), 4.29 (m, 1H), 3.80-3.53 (m, 2H), 3.39 (m, 3H), 1.39 (s, 3H), 1.31 (s, 6H). MS (UPLC-MS): 441 [M+H]+; tR (HPLC conditions f): 2.14 min.

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