An industrial production method of
linagliptin. According to the
molar ratio, 8-bromo-7-(2-butyne)-3-methylxanthine and 2-chloromethyl-4-methylquinazoline are added to the dipolar aprotic
organic solvent, and then the base is added and
potassium iodide, crystallized, filtered and dried to obtain intermediate I; according to the
molar ratio, intermediate I and (R)-3-tert-butoxycarbonylaminopiperidine were added to the dipolar aprotic
organic solvent, and alkali was added to analyze crystallized, filtered and washed to remove
inorganic salts, and the
solvent was removed under reduced pressure to obtain the crude product, which was then crystallized from
methanol and isopropanol to obtain intermediate II; according to the volume ratio, intermediate II and the deprotection
reagent were added to the reaction
solvent, and crystallized to obtain The crude product was recrystallized with
ethanol, filtered and dried to obtain the final product of
linagliptin. The method of the invention can greatly shorten the
production cycle, save production cost, obtain intermediates with higher purity, and better effect of removing impurities. The method is safe, reliable, simple and easy to operate, and has good
repeatability.