236406-33-0

872850-31-2

236406-33-0

Step 5: Preparation of tert-butyl 4-(2-hydroxyethyl)-4-methylpiperidine-1-carboxylate; 2-(1-(tert-butoxycarbonyl)-4-methylpiperidin-4-yl)acetic acid (3.54 g, 13.77 mmol) was dissolved in anhydrous tetrahydrofuran (THF) under argon gas protection and the solution was cooled to -15 °C. Borane-THF complex (13.8 mL, 1 M solution) was slowly added, followed by stirring the reaction mixture for 1 hour. The reaction mixture was allowed to gradually warm to room temperature and quenched by the slow addition of water (10 mL). Next, ethyl acetate (50 mL) was added for extraction, followed by washing with 2 M sodium hydroxide solution (40 mL) and water (40 mL). The organic layer was separated, washed with brine (20 mL), dried over anhydrous sodium sulfate and concentrated under reduced pressure to give an orange oily product (3 g, 90% yield). The product was confirmed by NMR hydrogen spectroscopy (CDCl3): δ 0.9 (s, 3H), 1.2-1.3 (m, 4H), 1.4 (s, 9H), 1.7 (t, 3H), 3.2 (m, 2H), 3.4 (m, 2H), 3.6 (t, 3H).