Dibenzyl malonate (I) was alkylated with 3-(trifluoromethyl)benzyl bromide (II) in the presence of Na in DMF to yield the 3-(trifluoromethyl)benzylmalonate (III). Further alkylation of (III) with 1,4-dibromobutane (IV) provided the bromobutyl derivative (V). Condensation of the known 6,7-dihydroimidazo[4,5-d][1,3]diazepin-8-one (VI) with bromide (V) in the presence of NaH and NaI furnished adduct (VII). The keto group of (VII) was then reduced to alcohol (VIII) employing NaBH4 in MeOH-CH2Cl2. Finally, hydrogenolysis of the benzyl ester groups of (VIII) in the presence of Pd/C and Et3N afforded the title dicarboxylate triethylammonium salt.