External vs. Internal Interactions in the Enantiodiscrimination of Fluorinated α‐Amino Acid Derivatives by Heptakis[2,3‐di‐O‐acetyl‐6‐O‐(tert‐butyldimethylsilyl)]‐β‐cyclodextrin, a Powerful Chiral Solvating Agent for NMR Spectroscopy

Abstract

AbstractNMR spectroscopic investigations involving extensive use of ROESY and DOSY techniques and comparison withsilylated‐acetylated linear dextrins as acyclic model compounds shed light on the origin of the phenomenon ofenantiodiscrimination of fluorinated α‐amino acid derivatives by heptakis[2,3‐di‐O‐acetyl‐6‐O‐(tert‐butyldimethylsilyl)]‐β‐cyclodextrin. The effectiveness and versatility of the cyclic derivatized oligosaccharide as a chiral solvating agent for the NMR determination of enantiomeric purity in the same class of compounds is demonstrated. A regular correlation between the relative positions of enantiomers' signals and absolute configurations is observed. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)