C-13 NUCLEAR MAGNETIC-RESONANCE SPECTROSCOPY OF SELECTED ADENINE NUCLEOSIDES - STRUCTURAL CORRELATION AND CONFORMATION ABOUT THE GLYCOSIDIC BOND

Structural correlations have been carried out from 13C chemical shifts (δ) and by analysis of 1J(CH) coupling constants, and the conformation about the glycosidic bond has been studied by means of the 3J(CH) vicinal coupling constants between C‐8 and H‐1′ of some adenine nucleosides such as adenosine (Ado), N(7)‐β‐D‐ribofuranosyladenine (N(7)‐Ado), N(9)‐ and N(7)‐β‐D‐xylofuranosyladenine (N(9)‐xylAde and N(7)‐xylAde), N(9)‐(3‐chloro‐3‐deoxy‐β‐D‐xylofuranosyl)adenine (3′‐Cl‐xylAde) and N(9)‐(2‐chloro‐2‐deoxy‐β‐D‐arabinofuranosyl)adenine (2′‐Cl‐araAde). The analysis of the influence on δ13C of the nature and configuration of the substituent in the carbohydrate fragment of the molecule has revealed two types of effects, namely, 1,2‐cis and 1,2‐trans. This approach, as well as the 3J(CH) values and the analysis of the C‐3′‐endo⇌C‐2′‐endo equilibrium of the carbohydrate fragment of nucleosides, and circular dichroism (CD) data, provides important information on the conformation about the glycosidic bond. The magnitudes of 3J(C‐4, H) are indicative of the position of attachment of the carbohydrate fragment to the heterocyclic base. Copyright © 1979 Heyden & Son Ltd.