Quantitative structure-activity relationships of purines I: Choice of parameters and prediction of pKa values

Linear free energy relationships were derived for several monosubstituted purines. The derived equations relate to the pKa to the Hammett constants sigma m and sigma p. A general linear free energy relationship was derived that permits calculation of the pKa of polysubstituted purines. The results suggest that correlation of biological data with standard parameters is feasible.