To a solution of 2-(4-chlorobenzoyl)benzoic acid (5 g, 19.2 mmol, 1 equiv.) in dry THF (20 mL) was added under nitrogen atmosphere thionylchloride (3.0 mL, 38.3 mmol, 2 equiv.) and 3 drops of anhydrous DMF. The reaction mixture was stirred for 4 h at room temperature and concentrated in vacuo. The resulting pale yellow oil was taken up in dry THF (20 mL), and (S)-4-chloro-α-methylbenzylamine (2.43 g, 15.6 mmol, 1.1 equiv.) and DIPEA (3.49 mL, 21.1 mmol, 1.1 equiv.) were added under nitrogen atmosphere. The reaction mixture was stirred overnight at room temperature and the solvents were removed in vacuo. The residue was taken up in EtOAc (100 mL), filtered, and the filtrate washed with water (3×50 mL) and brine (1×50 mL). The organic layer was dried over MgSO4, filtered and concentrated in vacuo to afford a solid, which was recrystallised (EtOAc/Petrol) as a white crystalline powder (3.10 g, 55%). 1H NMR (300 MHz, CDCl3): Mixture of two diastereoisomers: 7.74-7.09 (m, 13H, Ar—H and OH), 4.52 and 4.45 (q, J=6.9 Hz, 1H, CH*), 1.75 and 1.48 (d, J=7.2 Hz, 3H, CH3). 13C NMR (75 MHz, CDCl3): Mixture of two diastereoisomers: 166.94, 166.43, 149.17, 149.11, 142.01, 141.51, 139.65, 139.33, 133.24, 133.14, 132.90, 131.76, 131.60, 131.54, 131.47, 129.79, 129.71, 129.52, 128.67, 128.62, 128.26, 127.88, 127.84, 123.13, 122.74, 122.70, 91.19, 90.94, 51.22, 50.46, 20.21, 18.24. FTIR: 3103 (OH), 1665 (C═O) cm−1. m/z (ES): 398 [M+H]+. Anal.: calc. for C22H17Cl2NO2+0.3 H2O: C, 65.45; H, 4.40; N, 3.47. Found: C, 65.00; H, 4.30; N, 3.60.
