Central control method of midbody in dabigatran etexilate mesylate preparation process

The invention relates to the technical field of medicine synthesis and purification, in particular to a central control method of a midbody V 3-{2-[(4-amidino-anilino)methyl]-1-methyl-benzimidazole-5-[N-(2-pyridyl)formamido]}-ethyl propionate in the dabigatran etexilate mesylate preparation process. Dry gas HCl is introduced into a midbody III-ethanol mixture in synthesized dabigatran etexilate mesylate, the temperature is controlled within the range of -10 DEG C to 0 DEG C, the gas introduction end point is monitored in the period through titration, and therefore the midbody is obtained. The end point control and purification method is easy to operate, safe, accurate, capable of removing impurities, high in yield and purity and suitable for large-scale industrial production.