Design and Synthesis of Simple Macrocycles Active Against Vancomycin-ResistantEnterococci (VRE)

Chemoselective per-O-trimethylsilylation and homogeneous N-functionalisation of amino sugars

HomogeneousN-functionalisation of amino sugars can be achievedviaefficient CH₃CN-promoted hexamethyldisilazane per-O-trimethylsilylation.

Vancomycin analogs: Seeking improved binding of d-Ala-d-Ala and d-Ala-d-Lac peptides by side-chain and backbone modifications

In order to seek vancomycin analogs with improved performance against VanA and VanB resistant bacterial strains, extensive computational investigations have been performed to examine the effects of side-chain and backbone modifications. Changes in binding affinities for tripeptide cell-wall precursor mimics, Ac(2)-l-Lys-d-Ala-d-Ala (3) and Ac(2)-l-Lys-d-Ala-d-Lac (4), with vancomycin analogs were computed with Monte Carlo/free energy perturbation (MC/FEP) calculations. Replacements of the 3-hydroxyl group in residue 7 with small alkyl or alkoxy groups, which improve contacts with the methyl side chain of the ligands'd-Ala residue, are predicted to be the most promising to enhance binding for both ligands. The previously reported amine backbone modification as in 5 is shown to complement the hydrophobic modifications for binding monoacetylated tripeptides. In addition, replacement of the hydroxyl groups in residues 5 and 7 by fluorine is computed to have negligible impact on binding the tripeptides, though it may be pharmacologically advantageous.

The vancomycin-nisin(1-12) hybrid restores activity against vancomycin resistant Enterococci

Lipid II is a crucial component in bacterial cell wall synthesis [Breukink, E., et al. (1999) Science 286, 2361-2364]. It is the target of a number of important antibiotics, which include vancomycin and nisin [Breukink, E., and de Kruijff, B. (2006) Nat. Rev. Drug Discovery 5, 321-332]. Here we show that a hybrid antibiotic that consists of vancomycin and nisin fragments is significantly more active than the separate fragments against vancomycin resistant entercocci (VRE). Three different hybrids were synthesized using click chemistry and compared. Optimal spacer lengths and connection points were predicted using computer modeling.

Sweet antibiotics - the role of glycosidic residues in antibiotic and antitumor activity and their randomization

A large number of antibiotics are glycosides. In numerous cases the glycosidic residues are crucial to their activity; sometimes, glycosylation only improves their pharmacokinetic parameters. Recent developments in molecular glycobiology have improved our understanding of aglycone vs. glycoside activities and made it possible to develop new, more active or more effective glycodrugs based on these findings - a very illustrative recent example is vancomycin. The majority of attention has been devoted to glycosidic antibiotics including their past, present, and probably future position in antimicrobial therapy. The role of the glycosidic residue in the biological activity of glycosidic antibiotics, and the attendant targeting and antibiotic selectivity mediated by glycone and aglycone in antibiotics some antitumor agents is discussed here in detail. Chemical and enzymatic modifications of aglycones in antibiotics, including their synthesis, are demonstrated on various examples, with particular emphasis on the role of specific and mutant glycosyltransferases and glycorandomization in the preparation of these compounds. The last section of this review describes and explains the interactions of the glycone moiety of the antibiotics with DNA and especially the design and structure-activity relationship of glycosidic antibiotics, including their classification based on their aglycone and glycosidic moiety. The new enzymatic methodology 'glycorandomization' enabled the preparation of glycoside libraries and opened up new ways to prepare optimized or entirely novel glycoside antibiotics.

Importance of the Structure of Vancomycin Binding Pocket in Designing Compounds Active Against Vancomycin-resistant Enterococci (VRE)

16-Membered meta, para-cyclophanes mimicking the vancomycin binding pocket (D-O-E ring) are designed and synthesized. The structural features of these biaryl ether containing macrocycles are: a) the deletion of the carboxyl group of vancomycin's central amino acid (amino acid D); b) the elongation of the N-terminal; c) the presence of lipidated aminoglucose at the D-ring. Cycloetherification by way of an intramolecular nucleophilic aromatic substitution reaction (S(N)Ar) is used as a key step for the construction of the macrocycle. Minimum inhibitory concentrations for all of the derivatives are measured using a standard microdilution assay. Compounds 2a-2c and 3a-3c displayed weak activities against resistant strain Enterococcus faecalis L560 and were inactive against Enterococcus faecium resistant strain L2215.