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Rotational population dependences of the hydroxymethyl group in alkyl glucopyranosides: Anomers comparison
Author(s) -
Padrón Juan I.,
Vázquez Jesús T.
Publication year - 1997
Publication title -
chirality
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.43
H-Index - 77
eISSN - 1520-636X
pISSN - 0899-0042
DOI - 10.1002/(sici)1520-636x(1997)9:5/6<626::aid-chir34>3.0.co;2-o
Subject(s) - conformational isomerism , chemistry , anomer , absolute configuration , stereochemistry , alkyl , population , hydroxymethyl , anomeric effect , chirality (physics) , enantiomer , moiety , organic chemistry , molecule , nambu–jona lasinio model , demography , chiral symmetry breaking , physics , quantum mechanics , sociology , quark
A CD and 1 H NMR study of the rotamer population around the C5–C6 bond of alkyl α‐d‐glucopyranosides proved it to be dependent on the aglycon and its absolute configuration, showing a similar, but not identical, behavior to that of their β‐anomers. Thus, the population of the gt rotamer increased as the pK a of the aglycon increased, whereas the population of the tg and gg rotamers decreased, mainly that of the tg rotamer. The results showed the existence of a clear correlation between the stereoelectronic exo ‐anomeric effect and the rotamer distributions, the endo ‐anomeric effect not being directly involved. In addition, the 1 H NMR chemical shift differences (δ D –δ ROH ) of the alkyl α‐d‐glucopyranosides are characteristic of the absolute configuration of the aglycon, as occurred with the β‐anomers. Therefore, the absolute configuration of secondary chiral alcohols or the aglyconic moiety of natural glycosides can be determined independently of the anomeric configuration, a single enantiomer being sufficient. Chirality 9:626–637, 1997. © 1997 Wiley‐Liss, Inc.