GENERAL PROCEDURE: The chiral monomer (R)-1,2,3,4-tetrahydroisoquinoline-3-carboxylic acid (4.27 g, 20 mmol) was dissolved in methanol (20 mL) and the solution was cooled to 0 °C. Thionyl chloride (5.2 mL) was added slowly and dropwise with stirring. The reaction mixture was stirred at room temperature overnight. Upon completion of the reaction, the solvent was removed by rotary evaporator under reduced pressure to afford the white solid product (R)-1,2,3,4-tetrahydroisoquinoline-3-carboxylic acid methyl ester hydrochloride (5.29 g, 94.4% yield). The product was confirmed by 1H NMR (300 MHz, D2O, rt): δ 7.45-7.24 (m, 4H), 4.60 (d, J = 5.5 Hz, 1H), 4.56 (d, J = 5.4 Hz, 1H), 4.53 (br s, 1H), 3.93 (s, 3H), 3.53 (dd, J = 17.4, 5.5 Hz, 1H) 3.32 (dd, J = 17.3, 10.9 Hz, 1H). High resolution electrospray ionization mass spectrometry (HR ESIMS) showed m/z 192.1028 [M + H]+ (calculated value 192.1025), further confirming the structure of the product.
