Chloroacetyl chloride (1.7 mL, 21.5 mmol) To a solution of cis-5-(4-methoxy-2,3-dimethylphenyl)pyrrolidine-2-carboxylic acid ethyl ester (16.56 mmol) and Et3N (3.5 mL, 24.8 mmol) in CH2Cl2 (80 mL) at 0° C. The reaction mixture is stirred at 0° C. for 15 min and then at room temperature for 45 min. The mixture then poured into half-saturated aq. NaHCO3 (100 mL) and extracted with EtOAc. The extract is further washed with water (1×50 mL) and brine (1×50 mL). The aqueous washes are reextracted once with EtOAc, and the combined extracts are dried over Na2SO4, and concentrated. The crude material is used in the next step without further purification. 1H NMR (CDCl3, 400 MHz): 7.90 (d, J=8.6 Hz, 1H), 6.78 (d, J=8.6 Hz, 1H), 5.30 (dd, J=7.6, 3.6 Hz, 1H), 4.53 (t, J=8.0 Hz, 1H), 4.37-4.21 (m, 2H), 3.81 (s, 3H), 3.77, 3.65 (ABq, J=13.2 Hz, 2H), 2.50-2.41 (m, 1H), 2.26 (s, 3H), 2.24-2.14 (m, 1H), 2.19 (s, 3H), 2.09-2.00 (m, 1H), 1.96-1.89 (m, 1H), 1.35 (t, J=7.2 Hz, 3H). Electrospray MS: m/z 354 [M+1].
