Cyclomaltooligosaccharide-assisted spectroscopic discrimination of phthalimido-derived amino acids through the formation of molecular aggregates

Article abstract of DOI:10.1016/j.carres.2006.09.013

Spectroscopic evidence was used to demonstrate the formation of molecular associates in an aqueous solution of phthalimido tryptophan. These molecular associates are loosely formed through π-π aromatic stacking, properties that are not sufficient to cause NMR spectroscopic enantiomeric discrimination. A cyclomaltooligosaccharide with a larger cavity, such as cyclomaltooctaose (γ-cyclodextrin), is capable of forming a ternary complex with these molecular associates and enhances π-π aromatic stacking interactions, resulting in NMR enantiomeric discrimination. Electrospray-ionization mass spectroscopy (ESIMS) and NOESY two-dimensional NMR spectroscopic methods were used to study these complexes. Association constants and thermodynamic data for these cyclomaltooligosaccharide complexes were also estimated.