Chemoselective protection of the amino group of 2,3,5-trimethyl-4-aminophenol (I) with di-tert-butyl dicarbonate (Boc)2O in THF gives compound (II), which is then treated with NaH and (S)-glycidyl 3-nitrobenzenesulfonate (III) to yield epoxypropane (IV). On the other hand, treatment of 4,4'-difluorobenzophenone (V) with piperazine (VI) in acetonitrile in the presence of Et3N gives derivative (VII), which is reduced with Et3siH in the presence of H2SO4 and TFA to afford piperazine (VIII). Condensation of epoxypropane (IV) with piperazine (VIII) in refluxing 2-propanol furnishes compound (IX), which is finally converted into the desired product by first removal of the Boc group by exposure to TFA in CH2Cl2, followed by treatment with methanesulfonic acid (MeSO3H).

Chemoselective protection of the amino group of 2,3,5-trimethyl-4-aminophenol (I) with di-tert-butyl dicarbonate (Boc)2O in THF gives compound (II), which is then treated with NaH and (S)-glycidyl 3-nitrobenzenesulfonate (III) to yield epoxypropane (IV). On the other hand, treatment of 4,4'-difluorobenzophenone (V) with piperazine (VI) in acetonitrile in the presence of Et3N gives derivative (VII), which is reduced with Et3siH in the presence of H2SO4 and TFA to afford piperazine (VIII). Condensation of epoxypropane (IV) with piperazine (VIII) in refluxing 2-propanol furnishes compound (IX), which is finally converted into the desired product by first removal of the Boc group by exposure to TFA in CH2Cl2, followed by treatment with methanesulfonic acid (MeSO3H).