A simple and efficient procedure for the synthesis of benzimidazoles using air as the oxidant

Using molecular iodine in direct oxidative condensation of aldoses with diamines: an improved synthesis of aldo-benzimidazoles and aldo-naphthimidazoles for carbohydrate analysis

A practical method has been developed for conversion of unprotected and unmodified aldoses to aldo-benzimidazoles and aldo-naphthimidazoles. Using iodine as an oxidant or promoter in acetic acid solution, a series of mono-, di-, and trialdoses, including those containing carboxyl and acetamido groups, undergo an oxidative condensation reaction with o-phenylenediamine or 2,3-naphthalenediamine at room temperature to give the aldo-benzimidazole and aldo-naphthimidazole products in high yields. No cleavage of the glycosidic bond occurs under such mild reaction conditions. The composition analysis of saccharides is realized by the HPLC analysis of the fluorescent naphthimidazole derivatives.

Stabilization of Labile Carbonyl Addition Intermediates by a Synthetic Receptor

Products of unfavorable chemical equilibria are not readily observed because their high energy and increased reactivity result in low concentrations. Biological macromolecules use binding forces to access unfavorable equilibria and stabilize reactive intermediates by isolating them from the medium. In a similar vein, we describe here a synthetic receptor that allows direct observation of labile tetrahedral intermediates: hemiaminals formed in the reaction of an aldehyde carbonyl group with amines. The receptor encapsulates alkyl-substituted primary amines, then orients them toward a covalently tethered aldehyde function. The hemiaminal intermediates appear at high concentration, confined from the bulk solution and observable at ambient temperature by conventional nuclear magnetic resonance spectroscopy.

One-pot synthesis of 2-C-glycosylated benzimidazoles from the corresponding methanal dimethyl acetals

A series of 2-glycosyl-benzimidazoles with alpha-d-arabinopyranosyl, beta-d-galactopyranosyl, beta-d-glucopyranosyl, beta-d-mannopyranosyl, and beta-l-rhamnopyranosyl configurations were obtained in 52-73% yields from the corresponding C-glycosylmethanal dimethyl acetals and o-phenylenediamine under catalysis with hydrogen chloride or a strongly acidic cation-exchange resin. Intermediate benzimidazolines were spontaneously oxidized by air to produce the final products in the one-pot procedure. The prepared compounds did not show any inhibitory effect on the growth of 12 strains of five different species of pathogenic yeasts.

Design, microwave-assisted synthesis, and spasmolytic activity of 2-(alkyloxyaryl)-1H-benzimidazole derivatives as constrained stilbene bioisosteres

A simple, fast, and efficient method for the preparation of several 2-(alkyloxyaryl)-1H-benzimidazole derivatives is reported. Compounds were synthesized through a rapid one-pot three component reaction via microwave irradiation, starting from commercially available aldehydes and o-phenylenediamine, in the presence of Na(2)S(2)O(5) and solvent-free conditions. The design of these compounds explore the hypothesis that the stilbene framework could be mimicked with an appropriate 2-(Alkyloxyphenyl)benzimidazole scaffold. This framework has a similar structural motif as the 6-phenylnaphthalene and behaves like stilbene bioisosteres. The spasmolytic activity of these compounds was recorded using isolated rat ileum test. Compound 12 was the most active of the series, showing an IC(50) of 1.19 microM.