Click chemistry inspired facile one-pot synthesis of mannosyl triazoles and their hemagglutination inhibitory properties: The effect of alkyl chain spacer length between the triazole and phthalimide moieties in the aglycone backbone

An efficient one-pot synthesis of a new series of mannosyl triazoles has been achieved through CuAAC reaction where the alkyl chain spacer between the phthalimide moiety and the triazole ring in the aglycone backbone is varied from one methylene to six methylene units. The target compounds were evaluated in terms of their inhibitory potency against FimH using hemagglutination inhibition (HAI) assay. It was found that the length of four methylene units was the optimum for the fitting/binding of the compound to FimH as exemplified by compound 11 (HAI = 1.9 μM), which was approximately 200 times more potent than the reference ligand 1(HAI = 385 μM). The successful implementation of one-pot protocol with building blocks 1-7 and the architecture of ligand 11 will be the subject of our future work for developing more potent FimH inhibitors.

α-d-Mannoside ligands with a valency ranging from one to three: Synthesis and hemagglutination inhibitory properties

Six mono-, di-, and trivalent α-d-mannopyranosyl conjugates built on aromatic scaffolds were synthesized in excellent yields by Cu(I) catalyzed azide-alkyne cycloaddition reaction (CuAAC). These conjugates were designed to have unique, flexible tails that combine a mid-tail triazole ring, to interact with the tyrosine gate, with a terminal phenyl group armed with benzylic hydroxyl groups to avoid solubility problems as well as to provide options to connect to other supports. Biological evaluation of the prepared conjugates in hemagglutination inhibition (HAI) assay revealed that potency increases with valency and the trivalent ligand 6d (HAI = 0.005 mM) is approximately sevenfold better than the best meta-oriented monovalent analogues 2d and 4d (HAI ≈ 0.033 mM) and so may serve as a good starting point to find new lead ligands.

Effective anti-adhesives of uropathogenic Escherichia coli

Urinary tract infections (UTIs) caused by uropathogenic Escherichia coli (UPEC) are among the most common infectious diseases in humans. Due to their frequent occurrence in the community and nosocomial settings, as well as the development of resistance to the commonly prescribed antimicrobial agents, an enormous financial burden is placed on healthcare systems around the world. Therefore, novel approaches to the prevention and treatment of UTIs are needed. Although UPEC may harbour a plethora of virulence factors, type I fimbriae and P pili are two of the most studied adhesive organelles, since the attachment to host cells in the urinary tract is a crucial step towards infection. Design of receptor analogues that competitively bind to UPEC surface adhesins placed at the top of pili organelles led to the development of anti-adhesive drugs that are increasingly recognized as important and promising alternatives to antibiotic treatment of UTIs.

Assembly and inhibitory activity of monovalent mannosides terminated with aromatic methyl esters: The effect of naphthyl groups

A series of monovalent α-D-mannoside ligands terminated with aromatic methyl esters have been synthesized in excellent yields using the Cu(I) catalyzed azide-alkyne 1,3-dipolar cycloaddition ("click chemistry"). These mannosides were designed to have a unique aglycone moiety (tail) that combines a triazole ring attached to aromatic methyl esters via a six carbon alkyl chain. The mannose unit of these ligands was linked at the ortho, meta, and para positions of substituted methyl benzoates and 1-, 3-, and 6-substituted methyl 2-napthaoates. In hemagglutination assays, ligands (32A-38A) showed better inhibitory activities than the standard inhibitor, methyl α-D-mannopyranoside. Overall, the naphthyl-based mannoside ligand (37A) showed the best activity and therefore merits further development.