N⁷‐ and N⁹‐substituted purine derivatives: a ¹⁵N NMR study

Abstract

Abstract The 15 N NMR chemical shifts of N 7 ‐ and N 9 ‐substituted purine derivatives were investigated systematically at the natural abundance level of the 15 N isotope. The NMR chemical shifts were determined and assigned using GSQMBC, GHMBC, GHMQC and GHSQC experiments in solution. 15 N cross‐polarization magic angle spinning data were recorded for selected compounds in order to study the principal values of the 15 N chemical shifts. Geometric parameters obtained by using RHF/6–31G** and single‐crystal x‐ray structural analysis were used to calculate the chemical‐shielding constants (GIAO and IGLO) which were then used to assign the nitrogen resonances observed in the solid‐state NMR spectra and to determine the orientation of the principal components of the shift tensors. Copyright © 2002 John Wiley & Sons, Ltd.