Ammonium Chloride → ethyl (2S*,3R*)-2-(dibenzylamino)-3-hydroxy-pentanoate

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Reaction Steps

To a stirred solution of ethyl (2S*)-2-(dibenzylamino)-3-oxo-pentanoate [prepared as for example 47, step 1] (0.6 g, 1.76 mmol) in EtOH (30 mL), at rt, a solution of NH4Cl (1.89 g, 35.29 mmol) in H2O (8.0 mL) was added. NaBH4 (0.667 g, 17.6 mmol) was then added in small portions. After 1 h from the last addition, the reaction was quenched with H2O and the solvent evaporated. The crude mixture was taken up with H2O and CH2Cl2 and pH corrected to 9 with 20% NH4OH aqueous solution. After extraction, the organic phase was dried over Na2SO4, filtered, and concentrated in vacuo to give a crude product, as an oil. Purification by column chromatography using a Teledyne ISCO apparatus, eluting with Cy:AcOEt (90:10), gave the title compound (0.33 g, 55% over 2 steps), as a pure syn diastereoisomer, as a colorless oil. MS (ESI) m/z: 342 [M−H]+. 1H NMR (DMSO-d6) δ 0.75 (t, J=7.38 Hz, 3H), 1.26 (t, J=7.11 Hz, 3H), 1.30-1.52 (m, 2H), 3.14 (d, J=6.88 Hz, 1H), 3.67 (d, J=14.07 Hz, 2H), 3.85 (tt, J=4.61, 7.61 Hz, 1H), 4.08 (d, J=14.02 Hz, 2H), 4.11-4.25 (m, 2H), 4.66 (d, J=4.59 Hz, 1H), 7.20-7.27 (m, 2H), 7.28-7.41 (m, 8H).

Provenance & Evidence