Sodium Bicarbonate → (2R*,3S*)-3-hydroxy-2-[(4-phenylphenyl)-methoxycarbonylamino]-pentanoic acid

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Reaction Steps

To a stirred diastereomeric mixture containing (2R*,3R*) and (2R*,3S*)-2-amino-3-hydroxy-pentanoic acid (0.108 g, 0.81 mmol) and NaHCO3 (0.204 g, 2.43 mmol) in H2O (2.0 mL), at rt, the isomeric mixture containing (4-phenylphenyl)-methyl-2-pyridyl carbonate and (4-phenylphenyl)-methyl-2-oxopyridine-1-carboxylate (0.37 g, 1.22 mmol) [prepared as for example 17, step 1] in THF (2.0 mL) was added. After 15 h at rt, the crude mixture was rotary evaporated to remove the organics and subsequently extracted with Et2O (3×10 mL). The aqueous phase was acidified with 2.0 M HCl solution to pH 2-3 and subsequently extracted with AcOEt (3×20 mL). The organic fraction was dried over Na2SO4, filtered and concentrated to dryness to afford the title compound (0.206 g, 74% over 2 steps), as a diastereoisomeric mixture (anti:syn=8:2), as an off-white solid, which was used in the next step without further purification. MS (ESI) m/z: 361 [M−NH4]+; (ESI) m/z: 342 [M−H]−. 1H NMR (DMSO-d6) δ 0.87 (t, J=7.38 Hz, 3H), 1.36-1.55 (m, 2H), 3.55-3.69 (m, 1H), 3.94-4.05 (m, 1H), 4.73-4.99 (m, 1H), 5.08 (s, 2H), 7.29-7.54 (m, 6H), 7.57-7.77 (m, 4H), 11.38-13.49 (m, 1H) (reported data refer to the major anti diastereoisomer).

Provenance & Evidence