20 mg of 4-methylbenzenesulphonic acid hydrate are added to a solution of 200 mg of N-(2-hydroxyphenyl)-2-[4-(morpholin-4-yl)-6-oxo-1,6-dihydropyrimidin-2-yl]acetamide in 40 ml of toluene. The reaction mixture is brought to reflux overnight. After cooling to 0° C., the insoluble material formed is filtered off. The filtrate is concentrated to dryness under reduced pressure and the residue is then chromatographed on a silica gel column, eluent: CH2Cl2/MeOH: 98/02 then 90/10. 16 mg of 2-(1,3-benzoxazol-2-ylmethyl)-6-(morpholin-4-yl)pyrimidin-4(3H)-one are thus obtained in the form of a white solid, the characteristics of which are the following:
