D-Phenylalanine → (R)-2-Bromo-3-phenylpropionic acid
Reaktionsgleichung
N([O-])=O.[Na+].N[C@@H:6]([C:14]([OH:16])=[O:15])[CH2:7][C:8]1[CH:13]=[CH:12][CH:11]=[CH:10][CH:9]=1.[BrH:17].O>>[Br:17][C@H:6]([CH2:7][C:8]1[CH:13]=[CH:12][CH:11]=[CH:10][CH:9]=1)[C:14]([OH:16])=[O:15]Komponenten
4
Reaktionsbedingungen
- Temperatur
- 0 °C
Versuchsvorschrift
Sodium nitrite (27 g in water) is added at 0° C. to a solution of D-phenylalanine (40 g) in a mixture of 48% hydrobromic acid/water (1:1 by volume). The mixture is stirred for 30 minutes at 0° C. and then for 2 hours 30 minutes at a temperature close to 0° C. The reaction mixture is extracted with ether. The organic extracts are washed with water and a saturated sodium chloride solution and then dried over sodium sulphate. After filtration and concentration to dryness, the obtained residue is purified by distillation. (R)-2-Bromo-3-phenylpropanoic acid (33 g) is obtained which has the following characteristics: B.p.1kPa =154° C.; Rf =0.47 (methylene chloride/methanol). The yield is 60%.