Patent ID: 8791294

Claim:
A process for the stereoselective preparation of a substantially pure enantiomer of a compound of formula (I), alternatively its enantiomer (I′), wherein P is hydrogen or an amine protecting group, comprising the following steps: a) subjecting a compound of formula (III), alternatively its enantiomer (III′), to hydrogen in the presence of palladium/activated carbon to obtain the compound of formula (II), alternatively its enantiomer (II′); wherein R is (C 1 -C 8 )-alkyl; b) subjecting the compound of formula (II), alternatively its enantiomer (II′), to a hydrolysis reaction to obtain a compound of formula (I), alternatively its enantiomer (I′), wherein P is hydrogen and, optionally, subjecting said compound (I), alternatively its enantiomer (I′), to an amino group protection reaction.