The invention relates to a
drug synthesis method, and in particular relates to a preparation method of
sodium ibandronate. The preparation method comprises the following steps of: directly reacting 3-(N-methyl-N-n-amylamine) propionic
hydrochloride,
phosphorous acid with
phosphorus trichloride to obtain 1-hydroxyl-3-(methyl amylamine)-dimethylmethane-1,1-bipyrophosphoric acid
hydrochloride, directly forming salt with
sodium hydroxide after hydrolyzing so as to obtain crude
sodium ibandronate, and respectively re-crystallizing for one time through mixed solvents of
ethanol and water and
acetone and water so as to obtain sodium ibandronate. Any
solvent is not used in the step of synthesizing
pyrophosphoric acid hydrochloride;
solid-liquid reaction is carried out without stirring and post-treatment; products are directly used in the next step; a
reaction system is dispersed by using organic solvents, such as
chlorobenzene and
diethyl carbonate, in some reported methods; products are shaped as oil blocks and are not beneficial to stirring and post-treating after reacting; in contrast, the kinds of impurities in the products are reduced;
toxicity due to the organic solvents, such as
chlorobenzene and
diethyl carbonate, is eliminated; furthermore, the stirring difficulty is avoided; sodium ibandronate is prevented from being stuck on a stirrer and a
bottle wall; and thus, industrial production is conveniently carried out.