FIELD: chemistry.SUBSTANCE: maleic acid derivatives having general formulahave metallo-β-lactamase inhibiting activities. It is possible to recover anti-bacterial activities of β-lactam antibiotics against metallo-β-lactamase producing bacteria by combining the compound of general formula (I) with β-lactam antibiotics. The metallo-β-lactamase inhibitor is a compound of formula (I) or a pharmaceutically acceptable salt thereof, wherein R1 denotes C2-6-alkyl； C3-7-cycloalkyl, where said cycle can be substituted with a hydroxyl group or can be condensed with an aryl； hydroxymethyl； - C1-3-alkylene phenyl, where said phenyl group can be substituted with a hydroxyl group, C1-6-alkyl group, hydroxymethyl group, a -COOM group, where M denotes a hydrogen atom or a pharmaceutically acceptable cation, a -CO-NR22R23 group, where R22 and R23, which can be identical or different, denote a hydrogen atom or C1-6-alkyl, wherein the alkyl can additionally be substituted with an aminocarbonyl, or R22 and R23, together with a nitrogen atom with which they are bonded, can form a five- or six-member saturated heterocyclic ring containing 1-2 oxygen or nitrogen atoms, and the heterocycle can be substituted with a hydroxyl group or a C1-6-alkanoyloxy group, a -O-R24 group, where R24 denotes C1-6-alkyl, wherein the alkyl is optionally substituted with an aminocarbonyl, an amine group, a guanidine group or a five- or six-member saturated heterocycle, having 1-2 nitrogen atoms, -COOM, where M denotes a hydrogen atom, C1-6-alkyl or a pharmaceutically acceptable cation, or a five- or six-member unsaturated heterocycle, having 1-2 nitrogen atoms； - C0-1 alkylene heterocycle, where said heterocycle is a five- or six-member saturated or unsaturated heterocycle containing one nitrogen or oxygen atom and can be substituted with a hydroxyl group； - O-C1-6-alkyl； or - S-C1-6-alkyl, R2 denotes C1-6-alkyl, C3-7-cycloalkyl, where said cycle can be substituted with a hydroxyl group or can be condensed wi
