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

摘要

Among linear permethylated fructo-oligosaccharides containing various monosaccharide moieties at the reducingnterminal, MeSorFru3, MeGlc6Fru3, and MeFruNys showed high degrees of enantioselectivity toward bindingnsome amino acid 2-propyl ester salts. In particular MeFruNys indicated remarkable chiral discrimination towardn[ValOPri]u0001 (IR/IS-Dn = 0.14 corresponding to u0002ΔΔGenan = 1.2 kcal molu00021, S-selectivity) and [PheOPri ]u0001 (IR/IS-Dn = 0.18ncorresponding to u0002ΔΔGenan = 1.0 kcal molu00021, S-selectivity). The results of FAB mass, UV–visible spectrometries,nthermodynamic parameters, and NMR induced shifts provided evidence for the chiral discrimination of MeFruNysntoward amino acid ester salts in the “induced-fitting chiral recognition system”: the conformation of MeFruNysndrastically changes from a linear to a pseudo-ring structure with a given cation such as a chiral organic ammoniumnion or an alkali metallic ion. This is the first example of chiral discrimination of linear oligosaccharide derivativesntoward amino acid derivatives based on the induced-fitting chiral recognition mechanism.