NMR Study of Stacking Interactions between Thymine and 1,3-Dimethylxanthine Rings

Abstract

Stacking interactions between thymine and 1,3-dimethylxanthine rings of 7-[o-(2,4-diox0-1,2,3,4-tetrahydro-5-methyl-l-pyrimidinyl)alkyl]-1,3-dimethylxanthine were studied by means of 'H NMR spectroscopy in aqueous solutions and organic solvents. The spectra were compared with those of 1,l'-(a,oalkanediyl) bis [thymine] and 7,7'-(arm-alkanediy1)-bis [1,3-dimethylxanthine]. On the basis of the chemical shifts of the ring protons and methyl groups of thymine and xanthine rings, a stacked conformation between thymine and 1,3-dimethylxanthine rings in aqueous solutions was estimated.