Compounds of formula (I): ** Formula ** R1 represents a C1-C6 alkyl； Het represents a 3- to 7-membered non-aromatic monocyclic heterocycle containing one nitrogen atom and, optionally, 1 to 3 additional heteroatoms chosen from O, S, in which said nitrogen atom is attached to R1； A represents a single bond or a C1-C6 alkyl group； Each identical or different R2, R3, R4, R5, R6 is independently chosen from: * hydrogen * halo； azido； cyano； hydroxy； nitro； * I rent； alkoxy； alkylsulfanyl； alkenyl； alkynyl； alkenyloxy； alkenyloxy； alkenylsulfanyl； alkynylsulfanyl； cycloalkoxy； cycloalkylalkyl； whose alkyl, alkenyl, alkynyl or cycloalkyl part may be substituted with one or more of halo, hydroxy, polyhydroxy, alkoxy, hydroxyalkoxy, cyano, amino, aminoalkyl, alkylamino, dialkylamino, aminoalkylamino, aminoalkylaminocarbonyl, alkoxycarbonylamino, diarylmethylimino (where aryl is optionally substituted with one or more of hydroxy or halo), cycloalkenylimino (where cilalkenyl is optionally substituted with one or more of alkyl, OH), alkylsulfanyl, alkylsulfinyl, alkylsulfonyl, cycloalkyl, cycloalkenyl, guanidin, guanidino, alkylcarbonylguanidino, guanidino, guanidino , alkoxycarbonyl, alkoxycarbonylakylamino, alkoxycarbonylalkylcycloalkyl, alkoxycarbonylheterocyclyl, aminocarbonyl, alkylaminocarbonyl, alkylcarbonyl, alkylcarbonylalkyoxy, aryloxy, arylsulfanyl (heteroaryl, heteroaryl, heterocyl) or more of oxo, amino, imino), heteroaryloxy, heterocyclyloxy, heteroarylamino, heterocyclylamino, hydrazinocarbonyl, hydroxyalkylcycloalkyl, N-alkyl (thioureido), phthalimido, ureido, oxocycloalkenylamino substituted with amino, carbamimidoylheterocyclyl； * Not me； alkylamino； alkylcarbonyl； alkoxycarbonyl； alkylsulfanyl； alkylsulfinyl； alkylsulfonyl； alkylsulfonyloxy in which: alkyl can be substituted with one or more halo； and at least one of R2, R3, R4, R5, R6 is different from H each Xi, identical or different is chosen from -N>； =, -C (Ri)>； = and -C (Ri ')>； =, i represents
