The 1-[4,6-bis(allylamino)-1,3,5-triazin-2-yl]-4-piperidone hydrochloride (I) is added to [bis(4-fluorophenyl)methyl]amine (II) in dry methanol. The solution is acidified to pH 6 before adding NaBH3CN, resulting in 6-[4-[2,2-di-(4-fluorophenyl)ethylamino]piperidin-1-yl]-N,N'-diallyl-1,3,5-triazine-2,4-diamine (III). Treatment of (III) with methanesulfonic acid in isopropanol gives the bismethanesulfonate salt.