Compound presenting the general formula I in which: X represents an oxygen or sulfur atom； R1 represents a carbon, nitrogen, oxygen or sulfur atom； R1a represents a group CH, CH2, N or NH； R2 represents a covalent bond or a CH or CH2 group； R3 represents an optionally substituted C1-C6 alkyl group, an optionally substituted monocyclic, bicyclic or tricyclic C1-C13 group comprising between 1 and 5 heteroatoms selected from N, O and S, a monocyclic, bicyclic or tricyclic C6-C14 aryl group optionally substituted, an optionally substituted C3-C6 cycloalkyl group or an optionally substituted C3-C6 cycloalkenyl group, when R1 represents a carbon atom: R4 represents a hydrogen atom, a halogen atom, a monocyclic or bicyclic C1-C9 heterocyclic group optionally substituted comprising between 1 and 3 heteroatoms selected from N, O and S, or an optionally substituted monocyclic, bicyclic or tricyclic C6-C14 aryl group； R5 represents a hydrogen or halogen atom, a cyano group, or an optionally substituted hydroxy, mercapto, amino, carbamoyl, C1-C6 alkyl group, or a C1-C6 alkoxy group, or a group of the formula -C (>； = O) - R6 in which R6 represents an optionally substituted C1-C6 alkyl group or C1-C6 alkoxy group, an optionally substituted monocyclic or bicyclic C1-C9 heterocyclic group comprising between 1 and 3 heteroatoms selected from N, O and S, or an optionally substituted monocyclic, bicyclic or tricyclic C6-C14 aryl group； or R4 and R5 together represent an oxo group or an optionally substituted methylene group or a hydroxyimino group； or R4 and R5 together with R1 represent an optionally substituted unsaturated 4- to 6-membered ring comprising between 0 and 3 heteroatoms selected from N, O and S； when R1 represents an oxygen atom: R4 and R5 are missing； when R1 represents a nitrogen atom: one of R4 and R5 is missing, and the other is as defined above； when R1 represents a sulfur atom: each of R4 and R5, independently, is missing or represents an oxo group.Compuesto qu
