Methyl iodide → Valsartan Impurity 92

Participants

Reaction Steps

2 g (2R,4S)-5-Biphenyl-4-yl-4-tert-butoxycarbonylamino-2-methylpentanoic acid (1-a, R1=Boc, R2=H, R3=CO2H) prepared according to Example 2 in WO/2008/031567 is added to 2.55 g caesium carbonate. Dimethylformamide (4 ml) is then added. Methyl iodide (0.55 ml) is then added and the mixture is stirred for 16 h at room temperature. Water (10 ml) and isopropyl acetate (10 ml) are added. The phases are separated. The aqueous phase is washed with isopropyl acetate (2×10 ml). The combined organic phases are washed with 20% aqueous sodium chloride solution (15 ml) and then dried (MgSO4). The mixture is concentrated under reduced pressure to afford (2R,4S)-5-biphenyl-4-yl-4-tert-butoxycarbonylamino-2-methylpentanoic acid methyl ester (1-a, R1=Boc, R2=H, R3=CO2Me). 1H NMR (CDCl3): 1.18 (3H), 1.41 (9H), 1.51 (1H), 1.95 (1H), 2.66 (1H), 2.85 (2H), 3.70 (3H), 3.94 (1H), 4.36 (1H), 7.25 (2H), 7.35 (1H), 7.45 (2H), 7.53 (2H), 7.59 (2H).

Provenance & Evidence