Synthesis and biological activity of derivatives of glycopeptide antibiotics eremomycin and vancomycin nitrosated, acylated or carbamoylated at the N-terminal

Discovery of Peptide Antibiotics Composed of d-Amino Acids

A paucity of viable programs and pipelines for the discovery of new antibiotics poses a significant public health threat. The emergence of resistant strains against vancomycin is particularly dangerous in hospital settings. Here, we report the design of enantiomeric targets based on bacterial cell wall biosynthesis precursors that allow for selection and identification of short linear, cyclic and bicyclic peptides that are composed of d-amino acids. These compounds are active against Staphylococcus aureus, Methicillin-resistant S. aureus, and vancomycin-resistant Enterococci that possess moderately high antibacterial activity and furthermore display no toxicity to both human red blood cells and mammalian cells at these concentrations. This 'mirror image phage display' approach yielded templates that can serve as scaffolds for further improvements in activity-based structural modifications. This strategy has the potential to provide a new class of antimicrobials that are metabolically stable and have the promise for oral delivery. The use of this platform combined with traditional medicinal chemistry approaches could rapidly yield large numbers of new therapeutic lead compounds.

N-Terminus Alkylation of Vancomycin: Ligand Binding Affinity, Antimicrobial Activity, and Site-Specific Nature of Quaternary Trimethylammonium Salt Modification

A series of vancomycin derivatives alkylated at the N-terminus amine were synthesized, including those that contain quaternary trimethylammonium salts either directly at the terminal amine site or with an intervening three-carbon spacer. The examination of their properties provides important comparisons with a C-terminus trimethylammonium salt modification that we recently found to improve the antimicrobial potency of vancomycin analogues through an added mechanism of action. The N-terminus modifications disclosed herein were well-tolerated, minimally altering model ligand binding affinities (d-Ala-d-Ala) and antimicrobial activity, but did not induce membrane permeabilization that was observed with a similar C-terminus modification. The results indicate that our earlier observations with the C-terminus modification are sensitive to the site as well as structure of the trimethylammonium salt modification and are not simply the result of nonspecific effects derived from introduction of a cationic charge.

Membrane active vancomycin analogues: a strategy to combat bacterial resistance

The alarming growth of antibiotic resistant superbugs such as vancomycin-resistant Enterococci and Staphylococci has become a major global health hazard. To address this issue, we report the development of lipophilic cationic vancomycin analogues possessing excellent antibacterial activity against several drug-resistant strains. Compared to vancomycin, efficacy greater than 1000-fold was demonstrated against vancomycin-resistant Enterococci (VRE). Significantly, unlike vancomycin, these compounds were shown to be bactericidal at low concentrations and did not induce bacterial resistance. An optimized compound in the series, compared to vancomycin, showed higher activity in methicillin-resistant Staphylococcus aureus (MRSA) infected mouse model and exhibited superior antibacterial activity in whole blood with no observed toxicity. The remarkable activity of these compounds is attributed to the incorporation of a new membrane disruption mechanism into vancomycin and opens up a great opportunity for the development of novel antibiotics.

The effect of environment on the recognition and binding of vancomycin to native and resistant forms of lipid II

Molecular dynamics simulations and free energy calculations have been used to examine in detail the mechanism by which a receptor molecule (the glycopeptide antibiotic vancomycin) recognizes and binds to a target molecule (lipid II) embedded within a membrane environment. The simulations show that the direct interaction of vancomycin with lipid II, as opposed to initial binding to the membrane, leads most readily to the formation of a stable complex. The recognition of lipid II by vancomycin occurred via the N-terminal amine group of vancomycin and the C-terminal carboxyl group of lipid II. Despite lying at the membrane-water interface, the interaction of vancomycin with lipid II was found to be essentially identical to that of soluble tripeptide analogs of lipid II (Ac-d-Ala-d-Ala; root mean-square deviation 0.11 nm). Free energy calculations also suggest that the relative binding affinity of vancomycin for native, resistant, and synthetic forms of membrane-bound lipid II was unaffected by the membrane environment. The effect of the dimerization of vancomycin on the binding of lipid II, the position of lipid II within a biological membrane, and the effect of the isoamylene tail of lipid II on membrane fluidity have also been examined.

The next ten stories on antiviral drug discovery (part E): advents, advances, and adventures

This review article presents the fifth part (part E) in the series of stories on antiviral drug discovery. The ten stories belonging to this fifth part are dealing with (i) aurintricarboxylic acid; (ii) alkenyldiarylmethanes; (iii) human immunodeficiency virus (HIV) integrase inhibitors; (iv) lens epithelium‐derived growth factor as a potential target for HIV proviral DNA integration; (v) the status presens of neuraminidase inhibitors NAIs in the control of influenza virus infections; (vi) the status presens on respiratory syncytial virus inhibitors; (vii) tricyclic (1,N‐2‐ethenoguanine)‐based acyclovir and ganciclovir derivatives; (viii) glycopeptide antibiotics as antivirals targeted at viral entry; (ix) the potential (off‐label) use of cidofovir in the treatment of polyoma (JC and BK) virus infections; and (x) finally, thymidine phosphorylase as a target for both antiviral and anticancer agents. © 2009 Wiley Periodicals, Inc. Med Res Rev, 31, No. 1, 118–160, 2010

Synthesis and evaluation of vancomycin aglycon analogues that bear modifications in the N-terminal D-leucyl amino acid

The synthesis and biological evaluation of a series of vancomycin aglycon analogues bearing alternative residue 1 N-methyl-D-amino acids are described. The analogues were prepared to define whether H-bonding d-amino acids could improve the affinity for the model ligands N,N'-Ac(2)-L-Lys-D-Ala-D-Ala (2) and N,N'-Ac(2)-L-Lys-D-Ala-D-Lac (3) and improve antimicrobial activity against vancomycin-sensitive or vancomycin-resistant bacteria. Additionally, a series of analogues with appended nucleophiles (hydrazines and amines) on the residue 1 D-amino acids are described that were examined for their ability to react with the C-terminal ester of 3, forming a covalent attachment of L-Lys-D-Ala to the natural product analogues.

Inhibition of feline (FIPV) and human (SARS) coronavirus by semisynthetic derivatives of glycopeptide antibiotics

Various semisynthetic derivatives of glycopeptide antibiotics including vancomycin, eremomycin, teicoplanin, ristocetin A and DA-40926 have been evaluated for their inhibitory activity against feline infectious peritonitis virus (FIPV) and human (SARS-CoV, Frankfurt-1 strain) coronavirus in cell culture in comparison with their activity against human immunodeficiency virus (HIV). Several glycopeptide derivatives modified with hydrophobic substituents showed selective antiviral activity. For the most active compounds, the 50% effective concentrations (EC₅₀) were in the lower micromolar range. In general, removal of the carbohydrate parts of the molecules did not affect the antiviral activity of the compounds. Some compounds showed inhibitory activity against both, whereas other compounds proved inhibitory to either, FIPV or SARS-CoV. There was no close correlation between the EC₅₀ values of the glycopeptide derivatives for FIPV or SARS-CoV.

Structure-activity relationships in a series of semisynthetic polycyclic glycopeptide antibiotics

The main achievements in the development of methods for the design of semisynthetic antibiotics of a new generation belonging to the group of polycyclic glycopeptides directed against infections caused by multidrug-resistant bacteria and dangerous human and animal viruses are reviewed. The review is focused on the results obtained at the Gauze Institute in the area of chemical modification of natural antibiotics (eremomycin, vancomycin, teicoplanin, etc.) directed toward modification of their antibacterial and/or antiviral activity. A special emphasis is placed on the study of the mechanisms of action of these antibiotics, which could be the basis of a rational approach to their chemical modification involving the transformation of the inner binding pocket and the peripheral regions of the molecules that participate in the formation of their complexes with targets. The recently discovered antiviral activity of modified glycopeptides antibiotics is also discussed. A possibility of obtaining new highly active anti-HIV-1 and anti-HIV-2 preparations on the basis of hydrophobic derivatives of the aglycones of glycopeptide antibiotics was demonstrated. New semisynthetic derivatives of antibiotics that exhibit a high antibacterial activity in vivo, have good pharmacological characteristics, and are promising for practical use are described.