Synthesis of 4-(4-Aminocarbonylphenoxy)piperidine-1-carboxylic acid tert-butyl ester: To a solution of tetrahydrofuran (10 mL) with 4-hydroxybenzamide (343 mg, 2.50 mmol) was sequentially added N-Boc-4-hydroxypiperidine ( 503 mg, 2.50 mmol) and triphenylphosphine (656 mg, 2.50 mmol). Diethyl azodicarboxylate (1.15 mL, 2.50 mmol) was added slowly and dropwise under the cooling of an ice bath, followed by stirring the reaction mixture at room temperature overnight. Upon completion of the reaction, the mixture was concentrated and the resulting crude product was purified by silica gel column chromatography (eluent: chloroform/methanol=99/1) to afford tert-butyl 4-[4-(aminocarbonyl)phenoxy]piperidine-1-carboxylate, the target compound (169 mg, 21% yield).1H-NMR (DMSO-d6) δ: 1.39 (s, 9H), 1.45-1.60 (m , 1H), 1.89-1.92 (m, 1H), 3.13-3.20 (m, 2H), 3.62-3.69 (m, 2H), 4.61-4.66 (m, 1H), 6.99 (d, J=8.8 Hz, 2H), 7.15 (m, 1H), 7.80 (m, 1H), 7.81 (d, J=8.8 Hz, 2H).
