Gabapentin → 1-{{[(Cyclohexanon-2-yl)oxy]carbonyl}aminomethyl}-1-Cyclohexane Acetic Acid

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To a stirred solution of gabapentin (2.56 g, 15 mmol) and chlorotrimethylsilane (3.7 mL, 30 mmol) in dichloromethane (25 mL) at 0° C. under nitrogen atmosphere was added triethylamine in portions. After having stirred for 15 min at 0° C. the chloroformate (45) was added dropwise into the reaction mixture. The mixture was stirred at 0° C. for 2 h and then at room temperature for 2 h (monitored by TLC). The reaction mixture was concentrated in vacuo and the residue was poured into cold water (50 mL) and then acidified to about pH 5.0 using 0.1 N HCl. The crude product was then extracted using ethyl acetate (2×50 mL). The combined extracts were washed with brine (40 mL), dried over MgSO4 and the solvent removed in vacuo. The crude product was dissolved in acetone (25 mL) and treated using Amberlyst-15 (11.0 g) for 1.5 h (monitored by LC/MS). The reaction mixture was filtered and the filtercake was washed with acetone (2×15 mL). The combined extracts were evaporated under reduced pressure and the residue was purified using prep-HPLC/MS method to provide 1.71 g (55% yield) of compound 46 as a white solid. 1H NMR (CDCl3, 400 MHz): 5.42 (1H, t), 5.12 (1H, m), 3.35-3.16 (2H, m), 2.39 (4H, m), 1.80-1.40 (16H, m). MS (ESI): m/z=310.27 (M−H−), and 312.28 (M+H+).

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