Selective prepn process of (S)-Omeprazole with high antimer

The present invention relates to antimer selective catalytic oxidation process for preparing optical active antimer or optically pure antimer (S)-omeprazole. In the presence of the titanium containing catalyst in-situ created with metal titanium reagent and chiral glycol ligand and the oxidant, omeprazole sulfide is catalytically oxidized with antimer. Compared with the process utilizing tetraisopropanol titanium-diethyl tartrate system, the process of the present invention has the advantages of cheap material, high antimer selectivity and high yield. The present invention also relates to the preparation of (S)-omeprazole in neutralized state, partial crystallized state or completely crystallized state.