Triethylamine → (R)-alpha-hexyl-4-nitro-1H-imidazole-1-acetic acid

Participants

Reaction Conditions

Reaction Steps

To a solution of (-)-cinchonidine (48.0 g, 163 mmol) in 880 mL of distilled H2O at room temperature was added 2-(4-nitro-1H-imidazol-1-yl)-octanoic acid (83.0 g, 326 mmol) as a solution in 440 mL of ethanol. To this mixture was added triethylamine (11.7 mL). The mixture was then heated to 80° C., and the pH was maintained between 6.9 and 7.1 by the dropwise addition of triethylamine (5-10 mL). After the pH stabilized at 7.01, the solution was allowed to cool to room temperature, and let stand overnight whereupon crystallization of the (R)-2-(4-nitro-1H-imidazol-1-yl)octanoic acid-cinchonidine salt occurred. The crystalline salt was collected by filtration. The salt was then suspended in 200 mL ea. of ethyl acetate/H2O. To this suspension was added 1N HCl (750 mL). The layers were separated, and the aqueous was extracted with ethyl acetate (2×500 mL). The organic was combined, dried (Na2SO4), and concentrated in vacuo to provide 29.9 g (72%) of (R)-2-(4-nitro-1H-imidazol-1-yl)-octanoic acid as an off-white solid. M.pt. 116°-118° C.

Provenance & Evidence