A series of sugar sulfamate/sulfamide derivatives were prepared and assayed as inhibitors of three carbonic anhydrase (CA) isozymes, hCA 1, hCA 11 and bCA IV. Best inhibitory properties were observed for the clinically used antiepileptic drug topiramate, which is a low nanomolar CA 11 inhibitor, and possesses good inhibitory properties against the other two isozymes investigated here, similarly with acetazolamide, methazolamide or dichlorophenamide. The X-ray structure of the complex of topiramate with hCA 11 has been solved and it revealed a very tight association of the inhibitor, with a network of seven strong hydrogen bonds fixing topiramate within the active site, in addition to the Zn(II) coordination through the ionized sulfamate moiety. Structural changes in this series of sugar derivatives led to compounds with diminished CA inhibitory properties as compared to topiramate. (C) 2003 Elsevier Science Ltd. All rights reserved.