Premium
Carbon‐13 and proton magnetic resonance studies of some carbonyl‐bis‐(amino acid esters)
Author(s) -
Lochmüller C. H.,
Souter R. W.
Publication year - 1973
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.1270050802
Subject(s) - chemical shift , substituent , chemistry , proton , amide , isopropyl , carbon fibers , asymmetric carbon , resonance (particle physics) , inductive effect , spectral line , proton nmr , carbon 13 , medicinal chemistry , stereochemistry , organic chemistry , materials science , physics , optically active , particle physics , quantum mechanics , astronomy , composite number , composite material
A number of carbonyl‐bis‐(amino acid esters) have been examined by proton and carbon‐13 nuclear magnetic resonance techniques. All but one of the compounds were synthesized with two chiral centers of like‐configuration. In one series, the diastereotopic nonequivalence of isopropyl methyl groups attached to the asymmetric centers is apparent in both the proton and the carbon spectra, and the relative magnitude of the observed nonequivalence increases slightly with increasing ‘bulk’ of the neighboring ester groups. Carbon‐13 chemical shifts are reported, and a linear correlation of Taft σ* inductive constants with ester carbonyl carbon chemical shifts and with amide proton chemical shifts (for a series in which only variation of the ester substituent occurs) is presented. In addition, the effect in terms of chemical shift differences of keeping the same ester group at the asymmetric centers while varying the other substituent group, is examined.