Synthesis process of (L)-pantoprazole

The invention discloses a synthesis process of (L)-pantoprazole. The synthesis process comprises the following steps: 1) in the presence of iodine and alkali, 5-(difluoromethoxy)-2-mercapto-1H-benzimidazole and 2-(chloromethyl)-3,4-dimethoxypyridine hydrochloride are subjected to stirring reaction to obtain the pantoprazole thioether as shown in the formula I, and the pantoprazole thioether represented by the formula I shown in the specification and hydrogen peroxide are subjected to oxidation reaction in the presence of (R)-(-)-binaphthol phosphate to obtain the (L)-pantoprazole. The synthesis process is good in stereo selectivity, high in the product yield, mild in the conditions, simple in the steps and easier in after-treatment and purification. 本发明公开了种左旋泮托拉唑的合成工艺，其中，合成工艺包括：1)在碘和碱存在下，将5-二氟甲氧基-2-巯基-1H-苯并咪唑和2-氯甲基-3,4-二氧基吡啶盐酸盐搅拌反应得到式I所示的泮托拉唑硫醚；2)将式I所示的泮托拉唑硫醚在(R)-(-)-联萘酚磷酸酯存在下与过氧化氢反应氧化得到得到左旋泮托拉唑。本发明提供的左旋泮托拉唑的合成工艺，立体选择性好，产物收率高，并且条件温和、步骤简单，后处理纯化更加容易。