| 摘要 |
A compound of general formula (I), wherein R1 is a hydrogen atom, C1-C6 alkyl, C1-C6 alkoxy, cycloakyl or hydroxyalkyl, the alcoholic function of the hydroxyalkyl being free or protected; R2 is a free or esterified carboxy group or a carboxylate anion; R3 and R4 are each independently either hydrogen or C1-C6 alkyl, C1-C6 hydroxyalkyl or mercaptoalkyl, aminoalkyl or alkyl substituted with a quaternary ammonium group; cycloalkyl, arylalkyl or heterocyclyl-alkyl; a 5-6 membered, saturated or unsaturated heterocyclic ring, which can contain supplementary heteroatoms, such as oxygen, sulfur and nitrogen; an aryl group, or R3 and R4 form together a 3-7 membered, saturated or unsaturated heterocyclic ring, which can contain supplementary heteroatoms, such as oxygen, sulfur or nitrogen. |
