Ethanol → ethyl (2S*,3R*)-2-(dibenzylamino)-3-hydroxy-4-methyl-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] (2.76 g, 7.8 mmol) in EtOH (90 mL), at rt, a solution of NH4Cl (8.34 g, 156 mmol) in H2O (23 mL) was added. NaBH4 (2.95 g, 78 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 (1.33 g, 48% over 2 steps), as a pure syn diastereoisomer, as a colorless oil. MS (ESI) m/z: 356 [M−H]+. 1H NMR (DMSO-d6) δ 0.66 (d, J=6.69 Hz, 3H), 0.71 (d, J=6.68 Hz, 3H), 1.26 (t, J=7.09 Hz, 3H), 1.66 (h, J=6.63 Hz, 1H), 3.24 (d, J=7.12 Hz, 1H), 3.63 (d, J=13.94 Hz, 2H), 3.63 (m, 1H) 4.06 (d, J=14.06 Hz, 2H), 4.10-4.27 (m, 2H), 4.61 (d, J=4.60 Hz, 1H), 7.15-7.45 (m, 10H).

Provenance & Evidence