A solution of 20 parts of ethyl 3-methoxy-4-oxo-1-piperidinecarboxylate, 12 parts of (-)-α-methylbenzenemethanamine, 2 parts of a solution of thiophene in ethanol 4% and 200 parts of methanol was hydrogenated at normal pressure and at room temperature with 4 parts of palladium-on-charcoal catalyst 10%. After the calculated amount of hydrogen was taken up, the catalyst was filtered off and the filtrate was evaporated in vacuo. The residue was purified by HPLC using a mixture of hexane, trichloromethane and methanol (50:49.5:0.5 by volume) as eluent. The pure A-fractions were collected and the eluent was evaporated, yielding 15.62 parts (51%) of (-)-ethyl cis-3-methoxy-4-[(1-phenylethyl)amino]-1-piperidinecarboxylate as a residue (intermediate 103).
