Patent ID: 8471016

Claim:
A process for preparing a compound of formula I, or a pharmaceutically acceptable salt thereof, having the R-configuration of formula IA, or S-configuration of formula IB; selectively over the other enantiomer wherein, Ar is selected from aryl or heteroaryl which is unsubstituted or substituted with one to five substituents independently selected from the group consisting of halogen, C 1-8 alkyl, hydroxyl, cyano, nitro, alkoxy, and haloalkoxy, R 3 and R 4 are each independently hydrogen, C 1-8 alkyl, aryl, or alkylaryl or arylalkyl with a proviso that it is not 1-arylalkyl; or R 3 and R 4 together with the nitrogen atom to which they are attached to form a 4- to 7-membered heterocyclic ring system optionally containing an additional heteroatom selected from 0, S, N, said heterocyclic ring being unsubstituted or substituted with one to three substituents independently selected from oxo, hydroxy, halogen, C 1-4 alkoxy, and C 1-4 alkyl wherein alkyl and alkoxy are unsubstituted or substituted with one or more halogens; and said heterocyclic ring system being optionally fused with a 5 or 6-membered saturated or aromatic carbocyclic ring system or a 5 or 6-membered saturated or aromatic heterocyclic ring system containing one or two hetero atoms selected from O, S, and N, said fused ring system being unsubstituted or substituted with one or two substituents selected from hydroxy, amino, halo, C 1-4 alkyl, C 1-4 alkoxy, and haloalkyl; comprising, a. condensation of a compound of formula IIA, or its enantiomer of formula IIB, with a compound of formula III, or a salt thereof, to form a compound of formula IVA, or its enantiomer of formula IVB respectively; b. hydrogenolysis of the compound of formula IVA or its enantiomer a compound of formula IVB to the corresponding compound of formula IA or compound of formula IB, respectively; and c. optionally converting the compound of formula IA or IB to a pharmaceutically acceptable salt.