Keywords: 1-alkylsulfamides, 1,3-dialkyl-4-(alkylaminosulfonylimino)imidazolidin-2-ones, 4,5-dihydroxyimidazolidin-2-ones, 1,3-dimethyl-4-(benzenesulfonylimino)imidazolidin-2-one, X-ray structural analysis.Imidazolidin-2-one derivatives possess a broad spectrum of biological activity. In particular, hydantoins are used in medicine and agrochemistry as anticonvulsants [1, 2], anticancer preparations [3], fungicides [4], and herbicides [5]. On the other hand compounds containing a sulfamide fragment display bacteriostatic, hypoglycemic, diuretic, and herbicidal action [2, 6-8]. For several years the reactions of 4,5-dihydroxyimidazolidin-2-ones (DHI) with ureas and their hetero analogues have been among our scientific interests. Recently as a result of investigations carried out by us on the interaction of 1-alkyl and 1,3-dialkyl-DHI with sulfamide and amides of sulfonic acids, an unusual reaction has been detected [9] leading to 4,4'-sulfonyldiiminobis(1,3-dialkylimidazolidin-2-one) 1 and 4(5)-aryl(or alkyl)-sulfonyliminoimidazolidin-2-one 2, containing both pharmacophoric fragments. We later showed that the reaction of 1,3-dialkyl-DHI with aminoguanidine proceeds analogously with the formation of 1,3-dialkyl-4-guanidinoiminoimidazolidin-2-ones 3 [10]. N N O NSO 2 R 3 R 1 R 2 N N O R 1 NNHCNH 2 R 2 NH N N O R R NSO 2 N N N R O R 2 3 HCl 1 .With the aim of broadening the scope of the discovery, the reaction of 1,3-dialkyl-DHI 4a,b with 1-alkylsulfamides 5a-d under conditions analogous to the conditions of obtaining compounds 2 and 3 (methanol, HCl) (Scheme 1) has been investigated. __________________________________________________________________________________________