合成路线1

An asymmetric synthesis of pregabalin has been reported: Condensation of isobutyraldehyde (I) with acrylonitrile (II) by means of DBU and 2,6-di-tert-butyl-4- methylphenol (DBP) gives 3-hydroxy-4-methyl-2-methylenepentanenitrile (III), which is acylated with AcCl or Ac2O and pyridine to yield the acetate (IV). The carboxylation of (IV) by means of Pd(OAc)2, PPh3, CO and EtOH affords 3-cyano-4-methyl-3-hexenoic acid ethyl ester (Va-b), which is hydrolyzed with KOH in THF/water to provide the corresponding carboxylic acid potassium salt (VIa-b). Acidification of (VIa-b) with HCl, followed by reaction with tert-butylamine gives the corresponding salt (VIIa-b), which is reduced with H2 over a chiral (R,R)-rhodium catalyst [(R,R)-Rh] in THF/water to yield (S)-3-cyano-5-methylhexanoic acid butylammonium salt (VIII). Finally, the CN group of (VIII) is reduced with H2 over a sponge-Ni catalyst in basic (KOH) ethanol. Alternatively, intermediate (VIa-b) can be reduced with H2 over a chiral (R,R)-rhodium catalyst [(R,R)-Rh] in THF/water to yield (S)-3-cyano-5-methylhexanoic acid potassium salt (IX). Finally, the CN group of (IX) is reduced with H2 over a sponge-Ni catalyst in basic (KOH) ethanol.