The procedure was carried out as described in Raju et al, Organic Process Research & Development 2006, 10, 33-35, which is hereby incorporated by reference in its entirety. To a suspension of omeprazole sodium salt (5.53 g, 15.1 mmol, 1 equiv) in acetone (60 mL), were added a solution of diethyl-D-tartrate (3.1 g, 15.1 mol, 1 equiv) in acetone (3 mL), titanium (IV) isopropoxide (2.14 g, 7.55 mmol, 0.5 equiv) and triethylamine (4.75 g, 45.3 mmol, 3 equiv) at 35-40° C. To the resulting homogeneous solution was added L-(+)-mandelic acid (2.64 g, 17.4 mmol, 1.15 equiv). The mixture was cooled to ambient temperature and stirred for about 1-2 hours. The precipitate was filtered, washed with acetone (30 mL), and dried under reduced pressure to afford esomeprazole mandalate salt.
