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Conformational Dependence of One‐Bond C α ,H Spin Coupling in Cyclic Peptides
Author(s) -
Egli Huldrych,
Von Philipsborn Wolfgang
Publication year - 1981
Publication title -
helvetica chimica acta
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.74
H-Index - 82
eISSN - 1522-2675
pISSN - 0018-019X
DOI - 10.1002/hlca.19810640404
Subject(s) - chemistry , vicinal , sarcosine , cyclic peptide , stereochemistry , coupling constant , crystallography , peptide bond , alanine , oligopeptide , glycine , proline , amino acid , peptide , organic chemistry , biochemistry , physics , particle physics
Conformational effects on the one‐bond C α , H coupling constant have been studied in cyclic oligopeptides containing glycine, alanine, sarcosine and proline. The conformational contribution to 1 J (C α , H) can be described as being composed of a positive hyperconjugative term from the neighbouring N‐ p z orbital and a negative one from the carbonyl π‐system. For glycyl units, a quantitative relation between 1 J (C α ,H) and the vicinal interorbital angles Φ′ and Ψ′ is derived with maximum values Δ J (Ψ′) = + 14.0 Hz and Δ J (Ψ′) = −4.9 Hz. Applications to conformational analysis of cyclo ( L ‐Pro‐Gly) 3 , cyclo ( D ‐Ala‐ D ‐Ala‐ L ‐Ala‐ D ‐Ala‐ L ‐Ala‐ L ‐Ala) and cyclo (Sar) 8 are presented.