摘要：

In order to determine the stacking interactions between two parallel adenine rings oriented at different axis angles toward each other, we have synthesized a series of six different trimethylenebisadenine isomers. The per cent hypochromism, H, for the long wavelength ultraviolet absorption band for each of these compounds has been determined by comparison of the ultraviolet spectrum of the trimethylenebisadenine in aqueous solution with the composite spectrum of the two "half" molecules, the appropriate propyladenines. The H values obtained thereby for the trimethylenebisadenines are the following: 9,9′ isomer, 15%; N 6,N 6′, 16%; 8.8′, 21%; N 6, 9′, 16%; 8,9′, 19%; 7,9′, 16%. The per cent hypochromism follows a dependence upon the folded conformations available to the individual trimethylenebisadenines and offers the possibility of assessing the degree and orientation of overlap permitted or excluded for different ranges of H values.

展开