In: Chemistry
The flupirtine is an aminopyridine based non-opioid analgesic drug for acute and chronic pain. In 2013, the European Medicines Agency (EMA) had put the restriction to use of such drug due to the liver toxicity issues.
The synthesis of the flupirtine involves 4 steps which can be started from the commercially available 2,6-dichloro-3-nitropyridine which underwent selective amination at the 2-position to provide 6-chloro-3-nitropyridin-2-amine in good yield.
The 6-chloro-3-nitropyridin-2-amine underwent nucleophilic substitution with 4-fluoro-benzylamine to afford the 6-amino-2-benzylamino-5-nitropyridine intermediate which was subsequently reduced using SnCl2 to provide triaminopyridine intermediate. The regioselective addition of ethyl chloroformate to the 3-amino position of triaminopyridine intermediate proceeded in good yield to afford flupirtine.
The detail synthetic scheme is explained with the reaction condtions and reagents as below.