8-Bromo-7-but-2-ynyl-3-methyl-1-(4-methyl-quinazolin-2-ylmethyl)-3

To analyze the existing linagliptin and its key intermediate 8-bromo-7-(2-butynyl)-3,7-dihydro-3-methyl-1-[(4-methyl -2-quinazolinyl)methyl)-1H-purine-2,6-dione (11) synthesis method, find a synthetic route suitable for industrial production. Method: summarize the different synthetic routes. Results and conclusions: Route 2.2 has a relatively simple process and lower cost, which is more suitable for industrial production.

8-bromo-3,7-dihydro-3-methyl-1H-purine-2,6-dione is a key intermediate in the synthesis of the hypoglycemic drug linagliptin. The synthesis of 1 uses methyl urea and cyanoacetic acid as starting materials, and undergoes six-step reactions of condensation, cyclization, nitrosation, reduction, cyclization, and bromine with a total yield of 46.3%. The structures of all intermediates were confirmed by 1HNMR.

The present invention relates to a simple preparation method of high-purity linagliptin. Quinazoline, the key intermediate for the one-pot preparation of linagliptin 8 bromo 7 (2 butyne 1 base) 3,7 dihydro 3 methyl 1 [(4 methyl 2 quinazolinyl) methyl] 1H Purine 2,6 dione, the intermediate is separated by filtration, and then reacted with (R)3 aminopiperidine dihydrochloride to obtain a solution containing linagliptin. After the solution containing linagliptin is processed again, Deliraliptin pure product. The preparation of the key intermediate of the present invention adopts a one-pot method, which is convenient to operate and improves the yield. After the key intermediate is separated, it is reacted with (R)3 aminopiperidine dihydrochloride, thereby Obtaining high-purity linagliptin also meets the production and declaration requirements of pharmaceutical companies to the greatest extent.