The synthesis and anticonvulsant activity of novel heterocycles N-derivative-1,2,3-oxathiazolidine-4-one-2,2-dioxides, bioisosteres of trimethadione (TMD, oxazolidine-2,4-dione) and phenytoin (PHE), are described. TMD is an anticonvulsant drug widely used against absences seizures in the early 80's and PHE is an antiepileptic drug with a wide spectrum activity. The intermediates of synthesis of N-derivative-1,2,3-oxathiazolidine-4-one-2,2-dioxides, α-hydroxyamides, were obtained using microwave assisted synthesis. Anticonvulsant screening was performed in mice after intraperitoneal administration in the maximal electroshock seizure test (MES) and subcutaneous pentylenetetrazole seizures test (scPTZ). These new compounds showed a wide spectrum activity and were no neurotoxic in the RotoRod test. α-Hydroxyamides and N-derivative-1,2,3-oxathiazolidine-4-one-2,2-dioxides were 3-4700 times more potent than valproic acid in the MES test. Quantification of anticonvulsant protection was calculated (ED(50)) for the most active candidates; α-hydroxyamides 3a-c and 3e, and N-derivative-oxathiazolidine-4-one-2,2-dioxides 5a-c with ED(50) values of 9.1, 53.9, 44.6, 25.2, 15.1, 91.1 and 0.06mg/kg, respectively, in the MES test.