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Step 2. Synthesis of racemic-cis/trans-tert-butyl (6-methylpiperidin-3-yl) carbamate. Platinum(II) oxide (2.5 g) was added to a dry hydrogenation flask under argon protection. Subsequently, a solution of N-Boc-6-methyl-3-aminopyridine (33 g, 158.5 mmol) in acetic acid (300 mL) was added, and the resulting mixture was hydrogenated at 50 °C under 55 psi hydrogen pressure for 30 hours. The reaction was monitored by thin layer chromatography (TLC) (petroleum ether/ethyl acetate, 2:1) to confirm complete consumption of the feedstock. The reaction mixture was filtered and the filter cake was washed with methanol (50 mL x 2). The combined filtrates were concentrated under reduced pressure to afford tert-butyl (6-methylpiperidin-3-yl) carbamate (34 g, 100%) as a yellow oil (cis/trans ratio 2:1), which could be used in the subsequent steps without further purification.LC/MS analysis showed (M+H)+ of 215.2.

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