Scheme 1, Step B: Preparation of (R)-(-)-5-(hydroxymethyl)-2-pyrrolidinone (3)
To a solution of methanol (100 mL) containing methyl (R)-5-oxopyrrolidine-2-carboxylate (Intermediate 2, 13.2 g), sodium borohydride (10.5 g, 278 mmol) was added in batches at 0 °C. The reaction mixture was stirred continuously at 0 °C until the reaction was complete, followed by the addition of acetic acid (3 mL) to quench the reaction. The reaction mixture was concentrated and the residue was purified by silica gel column chromatography using methanol-chloroform (1:9, v/v) as eluent to afford the target product (12.9 g, 97% yield) as a colorless solid. Thin-layer chromatography (TLC) showed an Rf value of 0.33 (unfolding agent system: methanol-chloroform, 1:9, v/v); nuclear magnetic resonance hydrogen spectrum (1H-NMR, CDCl3) δ: 7.17 (s, 1H), 3.92 (s, 1H), 3.85-3.75 (m, 1H), 3.64-3.40 (m, 2H), 2.42-2.35 (m. 2H), 2.2-2.05 (m, 1H), 1.88-1.7 (m, 1H).
