Synthesis of 4-[2-(3,4-dimethoxybenzyl)cyclopentyl]-1,2-dimethoxybenzene Derivatives and Evaluations of Their Carbonic Anhydrase Isoenzymes Inhibitory Effects

Rearrangement of 1,6-bis(3,4-dimethoxyphenyl)hexane-1,6-dione (8) gave two isomeric products having cyclopentene moiety. Starting from the major product (3,4-dimethoxyphenyl)[2-(3,4-dimethoxyphenyl)cyclopent-1-en-1-yl]methanone (11), eight new compounds (16-23) were obtained by the reactions such as reduction (by catalytic hydrogenation and NaBH4 ), nitration, 1,4-addition, bromination, and esterification reactions. Carbonic anhydrases (CA, E.C.4.2.1.1) are ubiquitous metalloenzymes present in almost all living organism that catalyze a simple reaction, the conversion of carbon dioxide (CO2 ) and water (H2 O) to bicarbonate ion (HCO3 (-) ) and a proton (H(+) ). CA isoenzymes I and II (hCA I and II) inhibition effects of synthesized eleven new and four known compounds (8-13 and 15-23) were investigated. Inhibition studies of the hCA I and II with 4-[2-(3,4-dimethoxybenzyl)cyclopentyl]-1,2-dimethoxybenzene derivatives revealed that they possess effective inhibitory potency. Cytosolic hCA I and II isoenzymes were potently inhibited by new synthesized 4-[2-(3,4-dimethoxybenzyl)cyclopentyl]-1,2-dimethoxybenzene derivatives with Ki s in the range of 313.16-1537.00 nm against hCA I and in the range of 228.31-1927.31 nm against hCA II, respectively.