Reaktion #462304

Reaktionsgleichung

triethylamine

(-)-cinchonidine

2-(4-nitro-1H-imidazol-1-yl)-octanoic acid

triethylamine

→

(R)-2-(4-nitro-1H-imidazol-1-yl)-octanoic acid

Ausbeute 72.0%

Lösungsmittel

H2O

ethanol

Reaktionsbedingungen

Aufarbeitung

1. 1
   Temperaturto cool to room temperature
2. 2
   Sonstigelet stand overnight whereupon crystallization of the (R)-2-(4-nitro-1H-imidazol-1-yl)-octanoic acid-cinchonidine salt
3. 3
   FiltrationThe crystalline salt was collected by filtration
4. 4
   workup.ADDITIONTo this suspension was added in HCl (750 mL)
5. 5
   SonstigeThe layers were separated
6. 6
   Extraktionthe aqueous was extracted with ethyl acetate (2×500 mL)
7. 7
   Trocknendried (Na2SO4 )
8. 8
   Einengenconcentrated in vacuo

Vorschrift

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 in 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. Calculated for C11H17N3O4 : C, 51.76; H, 6.71; N, 16.46. Found: C, 51.89; H, 6.76; N, 16.20. [a]D -29.9 (c 1.00, ethanol).

Quelle