Trivalent Cluster Mannosides with Aromatic Partial Structure as Ligands for the Type 1 Fimbrial Lectin of Escherichia coli

Abstract

Mannose-specific adhesion of E. coli bacteria to their host cells is mediated by so-called type 1 fimbriae containing lectin domains present on the type 1 fimbrial FimH protein. The crystal structure of a FimH-FimC(chaperone) protein complex revealed a number of amino acids in the carbohydrate binding site with aromatic side chains. This finding is in keeping with earlier results showing high inhibitory potencies of aryl mannosides when tested as inhibitors of type 1 fimbriae-mediated bacterial adhesion. In addition, clustering of mannosyl moieties also led to favourable effects, as in the case of trivalent cluster mannosides such as (1). In order to combine both, i.e. the clustering approach and the advantage of an aromatic moiety, the herein presented study has emphasized the synthesis of three cluster mannosides (2), (3), and (4), as ligands for the type 1 fimbrial lectin, which contain a phenyl partial structure in different proximity to the core of the molecule. The inhibitory potencies of the new cluster mannosides were determined in enzyme-linked immunosorbent assays (ELISAs).