Quinine → (2S,3R)-2-(tert-butoxycarbonylamino)-3-hydroxy-3-(4-(trifluoromethyl)phenyl)propanoic acid

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Reaction Steps

To a solution of (R)-2-(tert-butoxycarbonylamino)-3-hydroxy-3-(4-(trifluoromethyl)phenyl)propanoic acid (LXXVIII) (35 g, 100 mmol) in Et2O (600 mL) was added quinine (34 g, 100 mmol) in portions. The reaction was stirred at room temperature for 30 min at which time the white precipitate (L-enantiomer salt) was filtered and washed with Et2O. The solid was taken up in EtOAc/aqueous KHSO4. The organic layer was washed with aqueous KHSO4, brine and dried over MgSO4. The solvent was removed in vacuo to give optically pure (Marfey test) (2S,3R)-2-(tert-butoxycarbonylamino)-3-hydroxy-3-(4-(trifluoromethyl)phenyl)propanoic acid (LXXIX) (12 g, 34 mmol, 68% yield). 1H NMR (DMSO-d6) δ ppm 1.33 (s, 9H), 4.09 (brs, 1H), 5.13 (brs, 1H), 5.56 (brs, 1H), 7.47 (d, J=8 Hz, 2H), 7.56 (d, J=8 Hz, 2H); 19F NMR (DMSO-d6) δ ppm −60.15; ESIMS found for C15H18F3NO5 m/z 348 (M−H)

Provenance & Evidence