General procedure C for the Boc deprotection. The N-Bocprotected amine (1.5 mmol, 1 equiv.) was dissolved in CH2Cl2 (3 mL), and 4 N HCl in dioxane (11.5 mmol, 10 equiv.) was added at 0 °C. The mixture was stirred for 3 h at 0 °C. The reaction was concentrated under reduced pressure to give the HCl salt, which was dissolved in aq. 0.05 M NaOH and extracted with EtOAc (3 × 15 mL). The combined organic layers were dried over Na2SO4, filtered, and concentrated under reduced pressure. The product was used for the next step without further purification.