Method for synthesizing and purifying dexlansoprazole

The invention mainly relates to an improved method for synthesizing dexlansoprazole by utilizing a Sharpless asymmetric oxidation method and an optimized method for purifying dexlansoprazole. According to the method, the total yield is above 40% and the purity of the product and the enantiomeric excess (e.e.) are both above 99.5%. The preparation method is simple, is low in cost and is suitable for industrial production.