Magnesium metal (1.33 grams) and Dichloromethane (3.7 ml) were added to methanol (111 ml) and stirred for 1–2 hours. The mass was cooled to a temperature of 5–10° C., esomeprazole obtained in Example 2 (37.0 grams) and methanol (111.0 ml) were added accompanied by stirring for 15–30 minutes. The reaction mass was decomposed into water (666 ml) at a temperature of 5–10° C. over a period of 45–60 minutes, and then further stirred for 30–45 minutes to separate the solid mass. The solid mass was filtered, and washed with water (222 ml). The thus obtained compound was dissolved in methanol (222 ml), and filtered off the solution to separate any excess magnesium. The solvent was removed from the filtrate to get the residual mass. The residual mass was crystallized in Acetone (278 ml) at a temperature of 0–5° C. to afford optically pure Esomeprazole magnesium trihydrate salt. The resulting product had the following characteristics. Weight: 11.5 g. Chiral Purity: ˜100%. Optical rotation: −125° (c=0.5% methanol)
