Preparation method of high-purity dipine drug key intermediate M2

The invention provides a preparation method of a key intermediate M2 of a high-purity dipine drug, and belongs to the technical field of preparation of drug intermediates, a dehydrating agent is added in the process of preparing the intermediate M2, and the dehydrating agent is an orthoester dehydrating agent. By adopting the method provided by the invention, the yield of the intermediate M2 is 84.3%, the HPLC (High Performance Liquid Chromatography) purity is 99.63%, and M2Z3 is 0.17%; 0.15% of M2Z4; the content of the impurities P0Z4 (namely M2Z3) and P0Z5 in the nicardipine further prepared from the nicardipine is determined as follows: the content of P0Z5 is less than 0.02%, and the content of P0Z4 is less than 0.02%. 本申请提供了一种高纯度地平类药物关键中间体M2的制备方法，属于药物中间体制备技术领域，在制备中间体M2的过程中添加脱水剂，所述脱水剂为原酸酯类脱水剂。采用本申请提供的方法，中间体M2的收率84.3％，HPLC纯度99.63％，M2Z3：0.17％；M2Z4：0.15％；其他杂质＜0.10％，进一步再制备尼卡地平中的杂质P0Z4(即M2Z3)和P0Z5的含量测定为：P0Z5＜0.02％，P0Z4＜0.02％。