The benzonaphthyridine system (III) was prepared by condensation of 1-Boc-4-piperidone (I) with 2-aminobenzonitrile (II) in the presence of ZnCl2. After acetylation of the 10-amino group of (III) with Ac2O in pyridine to afford (IV), the N-Boc protecting group was removed by treatment with HCl in dioxan-methanol, yielding 10-acetylamino-1,2,3,4-tetrahydrobenzo[b][1,6]-naphthyridine (V). The tricyclic amine (V) was then alkylated with the chiral sulfonate (VI), and the target compound was finally converted to the corresponding fumarate salt.