Preface

In this issue of Current Organic Chemistry several analytical methods to solve problems associated with the keto-enoltautomerism, molecular recognition and the stereochemistry of small and macromolecules are covered. E. Iglesias reviews work done on keto-enol / enolate equilibria in constrained media, such as aqueous solutions of surfactants forming micelles or cyclodextrins. The discussion offers new insights into enolization which is the standard textbook example of tautomeric rearrangements. K. Yannakopoulou and I. M. Mavridis describe the dependency of the host-guest recognition from structural parameters in the formation of inclusion complexes between cyclodextrins and guest molecules. The power of NMR spectroscopy and solid state x-ray crystallography for the analysis of the host-guest adducts is emphasized. The article of Y. Liu, B-H. Han and H-Y Zhang also deals with molecular recognition using modified cyclodextrins as model systems. Fluorescence spectroscopy, circular dichroism, UV-vis spectroscopy and 2D-NMR spectroscopy are applied to study the conformation and the complexation behavior of native and modified cyclodextrins. In the contribution of D. M. Hatch, J. O. Boles, Z. Li and L. A. “Pete” Silks, the incorporation of Se and Te containing amino acids in proteins is addressed. The advantage of introducing these heavy-atoms in proteins and peptides are to be seen in their ability to reduce the phase problem of macromolecular crystallography. Furthermore they are useful probes for vibrational and NMR spectroscopy. Finally, J. Gawronski and P. Skowronek present new achievments for stereochemical analysis by excition-coupled circular dichroism obtained by introducing extended π-chromophores. The aim of these reviews is to enable the reader to up-date his knowledge in advanced applications of well-established analytical techniques. The editors thank all authors for their efforts in preparing their articles.