The present invention relates to a process for the enantioselective preparation of the compound of formula (Ib), which process comprises a) reducing the (E)- or (Z)-form of a compound of formula (II), with an enantioselective reagent to a compound of formula (IIIa), and b) acylating the compound of formula (IIIa) with the compound of formula (IV), or c) coupling the compound of formula (IV) with the compound of formula (II), to give a compound of formula (V) and d) reducing compound of formula (V) in the presence of hydrogen, a catalyst and a chiral ligand, to the compound of formula (Ib).