30077-08-8Relevant articles and documents
Design, synthesis and biological evaluation of non-covalent AmpC β-lactamases inhibitors
Genovese, Filippo,Lazzari, Sandra,Venturi, Ettore,Costantino, Luca,Blazquez, Jesus,Ibacache-Quiroga, Claudia,Costi, Maria Paola,Tondi, Donatella
, p. 975 - 986 (2017/04/14)
Abstract: Bacterial resistance represents a worldwide emergency threatening the efficacy of all available antibiotics. Among the several resistance mechanisms developed by bacteria, β-lactamase enzymes?(BLs), which are able to inactivate most β-lactam core antibiotics, represent a key target to block, thus prolonging antibiotics half-life. Several approaches aimed at inhibiting β-lactamases have been so far undertaken, mainly involving β-lactam-like or covalent inhibitors. Applying a structure-based de novo design approach, we recently discovered a novel, non-covalent and competitive inhibitor of AmpC β-lactamase:?lead 1. It has a Ki of 1 μM, a ligand efficiency of 0.38 kcal mol?1 and lead-like physical properties. Moreover, it reverts resistance to ceftazidime in bacterial pathogens expressing AmpC and does not up-regulate β-lactamases expression in cell culture. Its features make it a good candidate for chemical optimization: starting from lead 1 crystallographic complex with AmpC, 11 analogs were designed to complement additional AmpC sites, then synthesized and tested against clinically resistant pathogens. While the new inhibitors maintain similar in vitro activity as the starting lead, some of them, in biological assays, extert a higher potency showing improved synergic activity with ceftazidime in resistant clinically isolated strains. Graphical Abstract: [InlineMediaObject not available: see fulltext.].
Mechanism of the Racemization of Amino Acids. Kinetics of Racemization of Arylglycines
Smith, Grant Gill,Sivakua, Thipamon
, p. 627 - 634 (2007/10/02)
In a study of the rates of racemization of substituted arylglycines at pH 10, the Hammett ? value was found to be surprisingly low, 1.15, suggesting a concerted reaction or charge stabilization in a manner other than by the substituent.The rate of methine hydrogen exchange was, however, the same as the rate of racemization, which argues against a concerted reaction mechanism.A pH profile study demonstrated that the most reactive species was the zwitterion +NH3CH(C6H5)CO2-> in basic media.The racemization reaction showed general-base catalysis when the buffer concentration was changed at constant ionic strength.Within the aryl series, the entropy of activation was more significant than the enthalpy of activation.The ΔS(excit.) ranged from -24.5 to +29.0 eu, while ΔH(excit.) values ranged from 19.9 to 20.4 kcal.Racemization of arylglycines followed reversible first-order kinetics similar to that found for aliphatic amino acids in solution.The extent of racemization was studied as a function of pH.The details of the mechanism of this reaction are presented in light of these data.