By the application of these methods, 1,2-benzothi-azine derivatives with 3-aminohydantoin moiety were pre-pared. Here, we report the synthesis of several new 3-aminohydantoinyl-1,2-benzothiazine derivatives and pro-pose an another mechanism of the cyclization to thehydantoins.3-Aminohydantoins 3a-d were prepared through cycli-zation of the condensation products 2a-d that were formedby heating amino acids and tert-butyl carbazate in quinolineaccording to the method of Lalezari.