CHIRAL RECOGNITION BY MULTI POINT INTERACTION STUDIED BY MICROCALORIMETRY AND HIGH RESOLUTIONALNMR SPECTROMETRY

2006 Fiscal Year Final Research Report Summary

• Project/Area Number: 17550127
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Single-year Grants
• Section: 一般
• Research Field: Functional materials chemistry
• Research Institution: Nagoya Institute of Technology
• Principal Investigator: YAMAMURA Hastuo Nagoya Institute of Technology, GRADUATE SCHOOL OF ENGINEERING, ASSOCIATE PROFESSOR (80220440)
• Project Period (FY): 2005 – 2006
• Keywords: titration calorimetry / chiral recoenition / cyclodextrin

Research Abstract

Complex stability constant, standard free energy (△G^O), reaction enthalpy (△H^O), and entropy change (T△S^O) for 1:1 inclusion complexation of the chiral amino acids Z-D/L-Trp (Z = benzyloxycarbonyl), Ac-D/L-Trp (Z = acetyl) with β-cyclodextrins (β-CDs) modified with D/L-Trp moiety and D/L-naphtylalaine moiety (D/L-Trp-β-CD and D/L-Naph-β-CDs) were determined by isothermal titration microcalorimetry. Interaction of Z-D/L-Trp with D/L-Trp-β-CD revealed no chiral discrimination. Affinities were smaller than that observed with native β-CD, however enthalpies were more negative in the case of D/L-Trp-β-CD. Affinities of Ac-D/L-Trp toward D/L-Trp-β-CD were higher than that toward native β-CD in 2-5 times. Binding properties of D-Trp-β-CD were quite different from the properties of L-Trp-β-CD, although both hosts exhibited no enantioselective abilities. Similarly to D/L-Trp-β-CD, D/L-Naph-β-CD also exhibited very low ability to discriminate between enantiomers of Ac-Trp. Upon interaction of two opposite enantiomers of Ac-Trp with L-Naph-β-CD quite different reaction enthalpies were observed. Nevertheless, stability of Ac-D-Trp + L-Naph-β-CD and that of Ac-L-Trp + L-Naph-β-CD complexes were practically the same due to common enthalpy-entropy compensation.