Conformational studies on substituted purines

CNDO/2 calculations are performed on 9-methyl-8-phenyl-6-thiopurine in order to determine the molecular equilibrium conformation. The two methyl hydrogens are found to be staggered to the ortho hydrogen on the phenyl ring, and the dihedral angle between the phenyl group and the purine system was found to be equal to 30°, in good agreement with experimental data. The results are discussed in relation to other conformational analyses performed with the CNDO/2 method.