FIELD: pharmaceutics.SUBSTANCE: present invention relates to a novel diaminopyrimidine derivative formula 1 or pharmaceutically acceptable salts thereof possessing properties of agonist of 5-HT4 receptors. In formula 1(Formula 1)R1 denotes a phenyl group substituted with one or more substitutes selected from a group consisting of hydroxy, amino, halogen, cyano, nitro, C1-5alkyl (where C1-5alkyl is optionally substituted with halogen), C1-5alkoxy, C1-5alkylthio, C1-5alkoxycarbonyl, aminosulphonyl and benzyloxycarbonylamino； or heteroaryl group selected from a group comprising pyridinyl, quinolinyl, chromenonyl, indolyl, indolinyl and benzimidazolyl, wherein heteroaryl group can be optionally substituted with one or more substitutes selected from a group consisting of C1-5alkyl (where C1-5alkyl is optionally substituted with halogen) and acetyl, R2 denotes hydrogen； C1-5alkyl group, optionally substituted with a substitute selected from a group consisting of hydroxy, C1-5alkoxy, benzylamino (where benzylamino is optionally substituted by halogen), phenylamino, C1-5alkylamino, C3-6cycloalkylamino and hydroxy-C1-5alkylamino； C1-5alkoxycarbonyl group or formyl group, R3 denotes hydrogen, hydroxyl group； C1-5alkyl group, optionally substituted with a substitute selected from a group consisting of C1-5alkoxycarbonylamino and di-C1-5alkylamino, or group selected from a group consisting of following formulae A, B, D and E (where symbol * in formulae A, B, D and E denotes position of attachment of said group of compounds of formula 1),R4 denotes hydrogen, R5 denotes C1-5alkyl group, optionally substituted phenyl or C2-6alkenyl group, optionally substituted phenyl or C3-6cycloalkyl, R6 denotes C1-10alkyl group, optionally substituted with a substitute selected from a group consisting of hydroxy, halogen, C1-5alkoxy, amino, C1-5alkoxycarbonylamino, benzyloxycarbonylamino, di-C1-5alkylamino, C1-5alkoxy-C1-5alkyloxy, phenoxy, benzyloxy, phenyl (where phenyl is optionally substitu
