The new imidazolinium, tetrahydropyrimidinium and tetrahydrodiazepinium salts were synthesized in good yield by the reaction of the corresponding N,N'-dialkylalkanediamine with triethyl orthoformate in the presence of ammonium chloride. All of the compounds were obtained, and spectroscopically characterized. The crystal structure for the 1,3-bis(4-benzyloxy-3-methoxybenzyl)-3,4,5,6-tetrahydropyrimidinium chloride (5 g) was determined by single-crystal X-ray diffraction. The biological properties of all novel compounds were tested and the influence of ring size and benzylic N-substituents on the biological activities were examined. Also, they were found as effective inhibitors against cytosolic carbonic anhydrase I and II isoforms (hCA I and II), and acetylcholinesterase (AChE) enzyme. Among these compounds, 1,3-bis(4-(1-piperidinyl)benzyl)-3,4,5,6-tetrahydropyrimidinium chloride (5 f) demonstrated the the best inhibition effects against hCA I, 1,3-bis(4-benzyloxy-3methoxybenzyl)-3,4,5,6-tetrahydropyrimidinium chloride (5 g) demonstrated the the best inhibition effects against cytosolic hCA II isoenzyme. On the other hand, 1,3-Bis(4-methylthiobenzyl)-3,4,5,6-tetrahydropyrimidinium chloride, (5e) demonstrated the the best inhibition effects against AChE enzyme.
