Dimethylformamide → (2R,4S)-2-methyl-4-((2-methylpropan-2-yl)oxycarbonylamino)-5-(4-phenylphenyl)pentanoic acid

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Reaction Steps

50 g of (2R,4S)-5-biphenyl-4-yl-4-tert-butoxycarbonylamino-2-methylpentanoic acid (3-a, R1=BOC, R2=R3=H) is added to dimethylformamide (80 ml). Cesium carbonate (69 g) is then added. Ethyl iodide (13.6 g) is then added and the mixture is stirred overnight at room temperature. Water (200 ml) is added to the mixture and the mixture is then extracted with isopropyl acetate (2×200 ml). The combined organic phases are washed with brine, dried (MgSO4) and concentrated in vacuo to give (2R,4S)-5-biphenyl-4-yl-4-tert-butoxycarbonylamino-2-methylpentanoic acid ethyl ester (3-a, R1=BOC, R2=H, R3=Et) (56 g). 1H NMR (DMSO): 1.12 (3H), 1.19 (3H), 1.36 (9H), 1.53 (1H), 1.84 (1H), 2.55 (1H), 2.75 (2H), 3.74 (1H), 4.05 (2H), 6.04 (1H), 7.23 (2H), 7.30 (1H), 7.41 (2H), 7.50 (2H), 7.57 (2H). m/z (ES+): 412 ([MH]+, 100%), 356 (63), 312 (73).

Provenance & Evidence