Gestreckte Gelatine als chirales Orientierungsmedium zur Unterscheidung von Enantiomeren durch NMR‐Spektroskopie

Abstract

NMR in Gummibärchen: Was als Spielerei begann, könnte interessante Anwendungsmöglichkeiten eröffnen: Gestreckte Gelatine unterscheidet als chirales Polymer Enantiomere anhand ihrer dipolaren Restkopplungen. Die Methode wird an einer Mischung von D‐Alanin und L‐Alanin demonstriert (siehe Bild).

Residual Dipolar Couplings (RDCs) Analysis of Small Molecules Made Easy: Fast and Tuneable Alignment by Reversible Compression/Relaxation of Reusable PMMA Gels

“…In 2004, the SAG concept was extended by Luy and co-workers to organic solvents, [21,22] and novel gels compatible with organic solvents were mainly developed by the same group. [23][24][25][26][27][28][29] Recently, Luy and co-workers extended the application of Kuchels apparatus to poly-(acrylamide) (PAAm) (aqueous) and polyacrylonitrile (PAN) ([D 6 ]DMSO) gels. [30] It involves the use of silicone tubing (outer diameter 4 mm and inner diameter 2.4 mm), placed inside an open-cut NMR tube and fixed with a PTFE plug at the bottom that permits the precise measurement of RDCs with rapid and reversible variation of the alignment strength.…”

Self‐Assembly of Folic Acid: A Chiral‐Aligning Medium for Enantiodiscrimination of Organic Molecules in an Aqueous Environment

“…[4] Many weak aligning media have been reported for chiral discrimination and the measurement of enantiomeric contents, such as polypep-A C H T U N G T R E N N U N G tides, [4] polynucleotides, [6,7] and polysaccharides, [8,9] as well as stretched gelatine gels [10] and collagen gels. [11] Some of these media are water compatible, [6][7][8][9][10] and many are also employed for deriving residual dipolar couplings to use as restraints for structure calculations of organic and biological molecules. [12][13][14][15][16][17] As far as the utility is concerned, each medium has its own benefits and limitations.…”

“…[5] In addition, in spite of weak alignment, the differential ordering effect (DOE) on anisotropic NMR parameters has a striking effect on the spectrum allowing the visualization of enantiomers. [4] Many weak aligning media have been reported for chiral discrimination and the measurement of enantiomeric contents, such as polypep-A C H T U N G T R E N N U N G tides, [4] polynucleotides, [6,7] and polysaccharides, [8,9] as well as stretched gelatine gels [10] and collagen gels. [11] Some of these media are water compatible, [6][7][8][9][10] and many are also employed for deriving residual dipolar couplings to use as restraints for structure calculations of organic and biological molecules.…”

Stereochemistry Determination by Powder X‐Ray Diffraction Analysis and NMR Spectroscopy Residual Dipolar Couplings

“…Since the pioneering work by Courtieu and co-workers on the determination of relative configuration by RDCs using poly-gbenzyl-l-glutamate (PBLG)/CDCl 3 , [8,9] more alignment media compatible with organic solvents are now available. [10][11][12][13][14][15][16][17][18][19][20][21][22] In natural products in particular, the power of RDCs for the resolution of configurational problems has been tested against known molecules such as menthol, [23] cyclosporin, [15] ludartin, [22] strychnine, [21,24] sphaeropsidin A, [11] sagittamide A, [25] archazolid A, [26] sodium cholate, [27] and even used, in the case of the novel glycoside sucro-neo-lambertellin [28] for the determination of the unknown configuration in several stereocenters. Another case is the configuration of a synthetic a-methylene-g-butyrolactone that could not be resolved by conventional means.…”