The relationship between proton–proton NMR coupling constants and substituent electronegativities. II—conformational analysis of the sugar ring in nucleosides and nucleotides in solution using a generalized Karplus equation
作者:
C. A. G. Haasnoot,
F. A. A. M. de Leeuw,
H. P. M. de Leeuw,
C. Altona,
期刊:
Organic Magnetic Resonance
(WILEY Available online 1981)
卷期:
Volume 15,
issue 1
页码: 43-52
ISSN:0030-4921
年代: 1981
DOI:10.1002/mrc.1270150111
出版商: John Wiley&Sons Limited
数据来源: WILEY
摘要:
AbstractThe relationship between vicinal NMR proton–proton coupling constants and the pseudorotational properties of the sugar ring in nucleosides and nucleotides is reinvestigated. Compared with our earlier study several important improvements are introduced: first, a new empirical generalization of the classical Karplus equation is utilized, which allows an accurate correction for the effects of electronegativity and orientation of substituents on3J(HH); second, empirical correlations between the parameters governing the conformation of β‐D‐furanosides (taken from an analysis of 178 crystal structures) were used to define proton–proton torsion angles as a function of the pseudorotation parametersPand Φm; and, third an iterative least‐squares computer program was devised to obtain the best fit of the conformational parameters to the experimental coupling constants. NMR data for the sugar ring in the following compounds were taken from the literature and analysed: 3′,5′‐cyclic nucleotides, a base‐stacked ribonucleotide, 2′‐anhydroarabinonucleosides, α‐D‐2′,2‐O‐cyclouridine, 2′‐ and 3′‐aminosubstituted ribonucleosides, 2′‐ and 3′‐deoxyribonucleosides. The present results confirm that the conformational properties found in the so
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