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The differentiation of diastereomers by 13 C NMR spectroscopy
Author(s) -
Schneider HansJörg,
Lonsdorfer Michael
Publication year - 1981
Publication title -
organic magnetic resonance
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.483
H-Index - 72
eISSN - 1097-458X
pISSN - 0030-4921
DOI - 10.1002/mrc.1270160215
Subject(s) - diastereomer , conformational isomerism , chemistry , substituent , vicinal , hydrogen bond , chemical shift , nuclear magnetic resonance spectroscopy , crystallography , halogen , deprotonation , solvent , solvent effects , stereochemistry , computational chemistry , molecule , organic chemistry , ion , alkyl
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.