Thiosemicarbazones active against Clostridium difficile

Amidinoquinoxaline N-oxides: synthesis and activity against anaerobic bacteria

We present herein an in-depth study on the activity of amidinoquinoxaline N-oxides 1 against Gram-positive and Gram-negative anaerobic bacteria. Based on 5-phenyl-2,3-dihydropyrimidoquinoxaline N-oxide 1a, the selected structural variations included in our study comprise the substituents α- to the N-oxide function, the benzofused ring, substitution and quaternization of the amidine moiety, and the amidine ring size. Compounds 1 showed good to excellent antianaerobic activity, evaluated as the corresponding CIM50 and CIM90 values, and an antimicrobial spectrum similar to metronidazole. Six out of 13 compounds 1 had CIM90 values significantly lower than the reference drug. Among them, imidazoline derivatives 1i-l were the most active structures. Such compounds were synthesized by base-promoted ring closure of the corresponding amidines. The N-oxides under study showed no significant cytotoxicity against RAW 264.7 cells, with high selectivity indexes. Their calculated ADME properties indicate that the compounds are potentially good oral drug candidates. The antianaerobic activity correlated satisfactorily with the electron affinity of the compounds, suggesting that they may undergo bioreductive activation before exerting their antibacterial activity.

29th Annual GP2A Medicinal Chemistry Conference

The 29th Annual GP₂A (Group for the Promotion of Pharmaceutical chemistry in Academia) Conference was a virtual event this year due to the COVID-19 pandemic and spanned three days from Wednesday 25 to Friday 27 August 2021. The meeting brought together an international delegation of researchers with interests in medicinal chemistry and interfacing disciplines. Abstracts of keynote lectures given by the 10 invited speakers, along with those of the 8 young researcher talks and the 50 flash presentation posters, are included in this report. Like previous editions, the conference was a real success, with high-level scientific discussions on cutting-edge advances in the fields of pharmaceutical chemistry.

Clostridium difficile drug pipeline: challenges in discovery and development of new agents

In the past decade Clostridium difficile has become a bacterial pathogen of global significance. Epidemic strains have spread throughout hospitals, while community acquired infections and other sources ensure a constant inoculation of spores into hospitals. In response to the increasing medical burden, a new C. difficile antibiotic, fidaxomicin, was approved in 2011 for the treatment of C. difficile-associated diarrhea. Rudimentary fecal transplants are also being trialed as effective treatments. Despite these advances, therapies that are more effective against C. difficile spores and less damaging to the resident gastrointestinal microbiome and that reduce recurrent disease are still desperately needed. However, bringing a new treatment for C. difficile infection to market involves particular challenges. This review covers the current drug discovery pipeline, including both small molecule and biologic therapies, and highlights the challenges associated with in vitro and in vivo models of C. difficile infection for drug screening and lead optimization.

Activation of C–H bonds of thiosemicarbazones by transition metals: synthesis, structures and importance of cyclometallated compounds

Transition metals (Pd^II, Pt^II, Ru^II, Rh^IIIand Ir^III) have induced activation of C–H bonds of thiosemicarbazones and yielded mono-, di-, tri- and tetra-nuclear complexes.

Progress in the discovery of treatments for C. difficile infection: A clinical and medicinal chemistry review

Clostridium difficile is an anaerobic, Gram-positive pathogen that causes C. difficile infection, which results in significant morbidity and mortality. The incidence of C. difficile infection in developed countries has become increasingly high due to the emergence of newer epidemic strains, a growing elderly population, extensive use of broad spectrum antibiotics, and limited therapies for this diarrheal disease. Because treatment options currently available for C. difficile infection have some drawbacks, including cost, promotion of resistance, and selectivity problems, new agents are urgently needed to address these challenges. This review article focuses on two parts: the first part summarizes current clinical treatment strategies and agents under clinical development for C. difficile infection; the second part reviews newly reported anti-difficile agents that have been evaluated or reevaluated in the last five years and are in the early stages of drug discovery and development. Antibiotics are divided into natural product inspired and synthetic small molecule compounds that may have the potential to be more efficacious than currently approved treatments. This includes potency, selectivity, reduced cytotoxicity, and novel modes of action to prevent resistance.

Synthesis, structures and antibacterial activities of benzoylthiourea derivatives and their complexes with cobalt

Four new thiocarbonyl fluorobenzamides and their complexes with cobalt have been synthesized and characterized by elemental analysis, FTIR, and (1)H NMR. Five crystal structures of the thioylbenzamides complexes of Co(PTCB)(3), Co(2FPTCB)(3), Co(4FPTCB)(3), Co(2FMTCB)(2) and Co(4FMTCB)(3) have been determined by X-ray diffraction. The antibacterial properties of these compounds against the bacteria, E. coli, Staphylococcus aureus, B. subtilis, P. aeruginosa, and Shewanella sp. were investigated. The experiments showed that both compounds and the complexes had the antibacterial activities against all of the studied bacteria. The thioylbenzamides had stronger controls for the bacteria of E. coli, S. aureus, B. subtilis and P. aeruginosa than their corresponding cobalt complexes. There was the contrary result against the bacteria of Shewanella sp. The para-substitution of fluorine atom increased antibacterial activities, while fluorine atom was substituted on ortho-benzoyl, the antibacterial activity weakened. The thioylbenzamides linked to piperidine instead of a morpholine group may increase the antibacterial activities.

Pyridine-derived thiosemicarbazones and their tin(IV) complexes with antifungal activity against Candida spp

[(n-Bu)Sn(2Ac4oClPh)Cl2] (1), [(n-Bu)Sn(2Ac4oFPh)Cl2] (2), [(n-Bu)Sn(2Ac4oNO2Ph)Cl2] (3), [(n-Bu)Sn(2Bz4oClPh)Cl2] (4), [(n-Bu)Sn(2Bz4oFPh)Cl2] (5) and [(n-Bu)Sn(2Bz4oNO2Ph)Cl2] (6) were obtained by reacting [(n-Bu)SnCl3] with 2-acetylpyridine-N4-orthochlorophenyl thiosemicarbazone (H2Ac4oClPh), 2-acetylpyridine-N4-orthofluorphenyl thiosemicarbazone (H2Ac4oFPh), 2-acetylpyridine-N4-orthonitrophenyl thiosemicarbazone (H2Ac4oNO2Ph), and with the corresponding 2-benzoylpyridine-derived thiosemicarbazones (H2Bz4oClPh, H2ABz4oFPh and H2Bz4oNO2Ph). The antifungal activity of the studied compounds was evaluated against several Candida species. Upon coordination of H2Bz4oNO2Ph to tin in complex (6) the antifungal activity increased three times against Candida albicans and Candida krusei and six times against Candida glabrata and Candida parapsilosis. The minimum inhibitory concentration (MIC) values of H2Ac4oNO2Ph and its complex (3) against C. albicans, C. parapsilosis and C. glabrata are similar to that of fluconazole. All studied compounds were more active than fluconazole against C. krusei.