Step B: (i) Synthesis of (R)-2-methylpyrrolidine hydrochloride; (i) (R)-tert-butyl 2-methylpyrrolidine-1-carboxylate (22.7 g, 123 mmol) was dissolved in 4 M hydrogen chloride in dioxane solution (100 mL) and the reaction was stirred for 30 min at room temperature. The progress of the reaction was monitored by thin layer chromatography (TLC, unfolding agent ratio 2:1 ethyl acetate/hexane) to confirm complete consumption of the raw material. After completion of the reaction, the solvent was removed by distillation under reduced pressure. The crude product was dissolved in a solvent mixture of acetonitrile and toluene and the solvent was again removed by distillation under reduced pressure. The resulting white solid was dried overnight under reduced pressure to give (R)-2-methylpyrrolidine hydrochloride (14.6 g) in 98% yield. The product was characterized by 1H NMR (400 MHz, CDCl3) with chemical shifts δ 1.55 (d, J = 6.57 Hz, 3H), 1.66-1.77 (m, 1H), 1.95-2.04 (m, 1H), 2.05-2.23 (m, 2H), 3.25-3.36 (m, 1H), 3.37-3.48 (m, 1H), and 3.62-3.74 (m, 1H), 9.38 (s, 1H), 9.86 (s, 1H).
