To a stirred mixture of (±)-1,2,3,4-tetrahydroisoquinoline-1-carboxylic acid (150 mg, 0.85 mmol) and dichloromethane (1.69 mL) was added di-tert-butyl dicarbonate (185 mg, 0.85 mmol) and triethylamine (177 μL, 1.27 mmol) sequentially at 0 °C. The reaction mixture was gradually warmed to room temperature with continuous stirring overnight. Upon completion of the reaction, the pH was adjusted to 3.0 with 1.0 N aqueous hydrochloric acid, followed by extraction of the reaction mixture with ethyl acetate (3 × 25 mL). The organic phases were combined, washed with saturated aqueous sodium chloride (50 mL), dried over anhydrous magnesium sulfate, filtered and the filtrate was concentrated under reduced pressure to afford 2-N-Boc-1,2,3,4-tetrahydroisoquinoline-1-carboxylic acid (235 mg, 100% yield). Mass spectral data (m/z): 222 ([M + 2H - t-Bu]+), 300 ([M + Na]+), 577 ([2M + Na]+).
