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The differentiation of diastereomers by 13C NMR spectroscopy

✍ Scribed by Hans-Jörg Schneider; Michael Lonsdorfer

Publisher
John Wiley and Sons
Year
1981
Tongue
English
Weight
477 KB
Volume
16
Category
Article
ISSN
0749-1581

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✦ Synopsis

Abstract

^13^C shifts are reported for diastereomers with halogen, oxygen and amino substituents which are mainly at vicinal chiral centres. The conformer populations underlying the ^13^C shift analysis can be verified by chemical means, such as change of temperature, solvent polarity (with dihalides), solvent hydrogen bonding capacity (with diols), deprotonation (with diacids) and by molecular mechanics calculations. The latter provide the basis for configurational and conformational assignments with a series of ephedrine derivatives. In accordance with the ^13^C shift observations, it is found that ephedrine derivatives predominate in conformations with a gauche O and N substituent arrangement, even in cases where hydrogen bonds are absent.

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