2,6-Lutidine → tert-Butyl (R)-2-[(trifluoromethylsulfonyl)oxy]propionate

関与物質

反応手順

Step 3′: t-Butyl (R)-2-(trifluoromethylsulfonyloxy)propionate was prepared from (R)-2-hydroxy-propionic acid tert-butyl ester (602 mg, 4.12 mmol), triflic anhydride (0.696 mL, 4.12 mmol) and 2,6-lutidine (0.480 mL, 4.12 mmol) in DCM (5 mL). To a suspension of ((S)-2-amino-3-(2′,5′-dichloro-biphenyl-4-yl)-propionic acid benzyl ester hydrochloride (600 mg, 1.38 mmol) in dichloromethane (10 mL) was added triethylamine (0.574 mL, 4.12 mmol) at 0° C. After stirred for 10 min, a half amount of the freshly prepared t-butyl (R)-2-(trifluoromethylsulfonyloxy)propionate was added at room temperature and stirred for 1 hour. Additional triethylamine (0.574 mL, 4.12 mmol) and the rest of t-butyl (R)-2-(trifluoromethylsulfonyloxy)propionate were added at room temperature and stirred for additional 2 hours. The reaction mixture was washed with H2O and the organic layer was concentrated under reduced pressure. The obtained residue was purified by silica gel column chromatography (EtOAc/heptane) to give (S)-2-(S)-1-tert-butoxycarbonyl-ethylamino)-3-(2′,5′-dichloro-biphenyl-4-yl)-propionic acid benzyl ester (580 mg). 1H NMR (400 MHz, CDCl3) δ 1.24 (t, 3H, J=6.8 Hz), 1.41 (s, 9H), 3.00-3.07 (m, 2H), 3.26 (dd, 1H, J=7.1, 13.9 Hz), 3.70 (dd, 1H, J=7.1, 7.1 Hz), 5.09 (s, 2H), 7.20-7.42 (m, 12H); MS: m/z (MH+) 528.

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