Cyclic homooligomers from sugar amino acids: Synthesis, conformational analysis, and significance

Sugar amino acids (SAAs) were designed as new building blocks carrying an a mino group and a carboxyl group on a carbohydrate scaffold. By exploiting s tandard solid- and solution-phase coupling procedures, linear and cyclic ho mooligomers containing glucosyluronic acid methylamine (Gum) were synthesiz ed. We achieved a high yield and a very short coupling time for the oligome rization and cyclization of sequences encopassing two, three, four, and six Gum units. The synthesis of cyclic oligomers containing only SAAs as repet itive units has not been reported before. The conformational preferences in aqueous solution of the cyclic derivatives and their applications as poten tial host molecules are described herein. Benzoic acid and p-nitrophenol we re chosen as model guest molecules to study the formation of cyclodextrin-l ike inclusion complexes. The complexation behavior of the cyclic hexamer wa s proved from three different points of view: chemical shifts, longitudinal relaxations (TI), and diffusion coefficients. All of them showed different values for host and guest molecules measured independently and in the pres ence of each other.