The paper studies the coupling reaction, through ester-type covalent bonds, of an oxazolone derived from the N-(m-nitrobenzoyl)-L-asparagic acid, the cycle of which is opened with an N-mustard derivative, on xanthan (a polysaccharide of microbian synthesis), in conditions of activation with dicyclohexyl carbodiimide. The coupling product has been characterized through elemental analysis and IR spectroscopy. For the establishment of the capacity of the active principle's controlled release by the polymer-active principle system thus obtained, active principle's release kinetics from the polysaccharide support, in conditions of basic hydrolysis, is studied. In vivo tests realized on mice proved the antitumoral activity of the compounds resulted by chemical bonding of the N-mustard derivative on xanthan.