Patent ID: 7947840

Claim:
A process for preparation of substantially enantiomerically pure esomeprazole of formula I: or a pharmaceutically acceptable salt thereof; which comprises: a) hydrolyzing a diastereomeric compound containing a mixture of 1-(S)-camphorsulfonyl-5-methoxy-2-[(3,5-dimethyl-4-methoxy-2-pyridy)methyl-(S)-sulfinyl]-1H-benzimidazole and 1-(S)-camphorsulfonyl-6-methoxy-2-[(3,5-dimethyl-4-methoxy-2-pyridyl)methyl-(S)-sulfinyl]-1H-benzimidazole of formula II: contaminated with an undesired diastereomeric compound containing a mixture of 1 -(S)-camphorsulfonyl-5-methoxy-2-[(3,5-dimethyl-4-methoxy-2-pyridyl)methyl-(R)-sulfinyl]-1H-benzimidazole and 1-(S)-camphor sulfonyl-6-methoxy-2-[(3,5-dimethyl-4-methoxy-2-pyridyl)methyl-(R)-sulfinyl]-1H-benzimidazole of formula III: with an hydroxide base selected from the group consisting of barium hydroxide, strontium hydroxide and cesium hydroxide, in a solvent to give the corresponding esomeprazole salts of formulae IV a , IV b or IV c : b) isolating the salt formed in step (a) as a crystalline solid; and c) neutralizing the esomeprazole salt formed in step (b) with an acid to obtain substantially enantiomerically pure esomeprazole of the formula I.