Remote-controlled nucleophilicity III: A valuable model to explain and predict the observed regioselectivity of the electrophilic attack on substituted 4-methylpyridine anions
Publication date: Available online 2 September 2019Source: Journal of Organometallic ChemistryAuthor(s): Andreas Opitz, Rainer KochAbstractIn a comparative study, the stability of lithiated methylpyridine and the reactivity of side chain functionalized 4-methylypridines were investigated. In contrast to gas phase calculations, the observed N-coordination of the lithium to 4-methylpyridine anions is shown to be a solvent effect. Furthermore, lithiated methylpyridines are predicted to be dimeric in THF.The regioselectivity of the picoline anion alkylation was subject to an in-depth study. The activation barriers for the methylation of methylpyridine in Cα, C(3), and N position were determined and compared with partial NPA charges in an attempt to explain the observed selectivity. While there is no correlation of the charges with the selectivity, the calculated activation energies not only fit well with experimental conditions but also parallel the predominantly observed regioselectivity of alkylation at the exocyclic carbon atom. In agreement with the experiment no attack at the C(3) is observed. In case of a Cα and N methylation mixture (for the 4-(phenyl(tosyl)methylpyridine), the activation barrier difference between the two pathways diminishes to almost 0 kcal/mol.Graphical abstract
CONCLUSION: Prevalence of antibiotic use was high not only versus other hospitals in the region but globally including Africa, coupled with significant evidence of sub-optimal prescribing. Swift action is needed to improve future prescribing to reduce AMR. One or two areas should initially be targeted for quality improvement including development of local guidelines, documentation of antibiotic indications and/or stop/review dates. PMID: 33034234 [PubMed - as supplied by publisher]
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Authors: Hammerschlag MR, Sharma R Abstract INTRODUCTION: Azithromycin was recommended as the first-line therapeutic regimen for treatment of genital infections in men and women by the Centers for Disease Control in 1998. A series of studies of azithromycin for treatment of rectal chlamydial infection in men who have sex with men (MSM) found that azithromycin was significantly less effective than doxycycline. AREAS COVERED: Literature on treatment of rectal C. trachomatis from 2000 through May 2020 was searched using PubMed. Retrospective and observational studies were identified documenting the frequency and t...
Authors: Reissier S, Cattoir V Abstract INTRODUCTION: Streptogramins (pristinamycin and quinupristin-dalfopristin) can be interesting options for the treatment of infections due to Gram-positive cocci, especially multidrug-resistant isolates. AREAS COVERED: This review provides an updated overview on structural and activity characteristics, mechanisms of action and resistance, pharmacokinetic/pharmacodynamic and clinical use of streptogramins. EXPERT OPINION: The streptogramin antibiotics act by inhibition of the bacterial protein synthesis. They are composed of two chemically distinct compounds, namely typ...
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