Angewandte Chemie International Edition

Angewandte Chemie International Edition
Early View (Articles online in advance of print)
Published Online: 8 Jun 2010

High-Resolution Studies of Uniformly 13C,15H-Labeled RNA by Solid-State NMR Spectroscopy

Alexey V. Cherepanov, Dr., Clemens Glaubitz, Prof. Dr., Harald Schwalbe, Prof. Dr.

Keywords: conformational analysis • freeze-quenching • NMR spectroscopy • RNA • solid-state structures

Abstract: Chilling out: Solid-state 13C NMR correlation spectroscopy was used to assign the signals of a uniformly labeled RNA hairpin infrozen aqueous solution. Conformational analysis shows that solutions of biologically relevant RNAs can freeze withoutsignificant changes in RNA structure and without critical loss of resolution and sensitivity in NMR experiments.

10.1002/anie.200906885


Angewandte Chemie International Edition
Early View (Articles online in advance of print)
Published Online: 8 Jun 2010

The Elusive Enamine Intermediate in Proline-Catalyzed Aldol Reactions: NMR Detection, Formation Pathway, and Stabilization Trends

Markus B. Schmid, Kirsten Zeitler, Dr., Ruth M. Gschwind, Prof. Dr.

Keywords: aldol reaction • enamines • NMR spectroscopy • organocatalysis • proline catalysis

Abstract: The missing link: The elusive enamine intermediate of nucleophilic proline catalysis was detected and stereochemicallycharacterized by NMR analysis of the aldehyde self-aldolization reaction in dipolar aprotic solvents. NMR exchange spectroscopy(EXSY) was used to observe direct enamine formation from oxazolidinones. Additionally, the stabilization of the intermediate bythe appropriate choice of solvent and substitution pattern on the aldehyde is presented.

10.1002/anie.200906629