| abstract |
The invention relates to a process for the preparation of pyrido[2,1- a ] isoquinoline derivatives of the formula n n n n n n n n n n wherein R 2 , R 3 and R 4 are as defined in the specification, comprising the steps of a) catalytic asymmetric hydrogenation of an enamine of the formula n n n n n n n n n n wherein R 1 is lower alkyl, in the presence of a transition metal catalyst containing a chiral diphosphane ligand, b) introduction of an amino protecting group Prot and c) amidation of the ester to form an amide of formula n n n n n n n n n n wherein R 2 , R 3 , R 4 and Prot are as defined in the specification. |