A mixture of 1.8 parts of 1-(3-chloropropyl)-1,3-dihydro-2H-benzimidazol-2-one, 2.7 parts of 9-[(4-fluorophenyl)methyl]-8-(4-piperidinylmethyl)-9H-purine, 1 part of sodium carbonate and 45 parts of N,N-dimethylformamide was stirred and heated overnight at 70° C. After cooling, the reaction mixture was poured into water. The product was extracted with trichloromethane. The extract was dried, filtered and evaporated. The residue was purified by column chromatography over silica gel using a mixture of trichloromethane and methanol, saturated with ammonia, (95:5 by volume) as eluent. The pure fractions were collected and the eluent was evaporated. The residue was converted into the (E)-2-butenedioate salt in ethanol. The salt was filtered off and dried, yielding 2.85 parts (45.9%) of 1-[3-[4-[[9-[(4-fluorophenyl)methyl]-9H-purin-8-yl]methyl]-1-piperidinyl]-propyl]-1,3-dihydro-2H-benzimidazol-2-one (E)-2-butenedioate(1:2); mp. 186.2° C. (compound 114).
