Chiral discrimination of fructo-oligosaccharides toward amino acid derivatives by induced-fitting chiral recognition

Among linear permethylated fructo-oligosaccharides containing various monos accharide moieties at the reducing terminal, MeSorFru(3), MeGlc(6)Fru(3), a nd MeFruNys showed high degrees of enantioselectivity toward binding some a mino acid 2-propyl ester salts. In particular MeFruNys indicated remarkable chiral discrimination toward [ValOPr(i)](+) (I-R/IS-Dn = 0.14 correspondin g to -Delta DeltaG(enan) = 1.2 kcal mol(-1), S-selectivity) and [PheOPr(i)] (+) (I-R/IS-Dn = 0.18 corresponding to -Delta DeltaG(enan) = 1.0 kcal mol(- 1), S-selectivity). The results of FAB mass, UV-visible spectrometries, the rmodynamic parameters, and NMR induced shifts provided evidence for the chi ral discrimination of MeFruNys toward amino acid ester salts in the "induce d-fitting chiral recognition system": the conformation of MeFruNys drastica lly changes from a linear to a pseudo-ring structure with a given cation su ch as a chiral organic ammonium ion or an alkali metallic ion. This is the first example of chiral discrimination of linear oligosaccharide derivative s toward amino acid derivatives based on the induced-fitting chiral recogni tion mechanism.