A 500 mL hydrogenation vessel was charged with 2.0 g platinum(II)oxide and purged with nitrogen. Ethyl 5-(3-pyridyl)-2-methylbenzoate (19.57 g, 81.10 mmol) was added as a solution in 200 mL acetic acid. The suspension was hydrogenated at 45 psi for 18 h. The catalyst was filtered through celite and the filter plug was washed with 200 mL acetic acid. The filtrate was concentrated under reduced pressure. The resultant oil was taken up in 500 mL water and made basic with 5N aqueous sodium hydroxide. This basic layer was extracted with ethyl acetate (2×500 mL) and the extracts were combined and dried over anhydrous sodium sulfate, filtered and concentrated under reduced pressure. The resultant oil was taken up in 200 mL hot ethanol. L-(+)-tartaric acid (12.17 g, 81.1 mmol) was added into the ethanol solution and was allowed to stir at ambient temperature for 48 h, forming a white precipitate that was collected by filtration. The white solid was recrystallized from hot 5% H2O/ethanol (300 mL) and then from 350 mL hot 20% H2O/ethanol to yield 11.25 g (35%, 95.8% ee) of (S)-ethyl 5-(3-piperidinyl)-2-methylbenzoate-L-tartaric acid salt as a white solid. The mother liquors were combined and concentrated under reduced pressure. The resultant oil was taken up in 300 mL water and made basic with 5N aqueous sodium hydroxide. This basic layer was extracted with ethyl acetate (2×300 mL) and the extracts were combined and dried over anhydrous sodium sulfate, filtered and concentrated under reduced pressure. The resultant oil was taken up in 200 mL hot ethanol. D-(−)-tartaric acid (6.82 g, 45.4 mmol) was added into the ethanol solution and was allowed to stir at ambient temperature for 48 h, forming a white precipitate that was collected by filtration. The white solid was recrystallized from hot 5% H2O/ethanol (300 mL) and then from 350 mL hot 20% H2O/ethanol to yield 13.51 g (42%, 100% ee) of (R)-ethyl 5-(3-piperidinyl)-2-methylbenzoate-D-tartaric acid salt as a white solid.
