General procedure for the synthesis of tert-butyl 3-hydroxyazepane-1-carboxylate from N-Boc-3-azepanone: Sodium borohydride (NaBH4) (0.98 g, 25.8 mmol) was added batchwise to a solution of N-Boc-3-azepanone (5.5 g, 25.8 mmol) in methanol (55 mL) at 0 °C, and the progress of the reaction was monitored by thin-layer chromatography (TLC). Upon completion of the reaction, the pH of the reaction mixture was adjusted to 5 to 6 with hydrochloric acid (HCl) solution, followed by filtration and extraction with dichloromethane (DCM, 100 mL x 3). The organic phases were combined, dried with anhydrous sodium sulfate (Na2SO4), filtered and concentrated under reduced pressure to afford tert-butyl 3-hydroxyazepane-1-carboxylate (oil, 4.8 g, 87% yield). The structure of the product was confirmed by 1H NMR (400 MHz, d6-DMSO): δppm 3.95-3.93 (m, 1H), 3.71-3.62 (m, 2H), 3.40 (m, 1H), 3.32-3.28 (m, 1H), 3.03 (m, 1H), 1.88-1.65 (m, 4H), 1.55-1.36 ( m, 11H).
