Intra- and Intermolecular Interactions in Azanucleosides

of Chemistry, University of North Carolina, Chapel Hill, N.C. 27514, U.S.A. 

It is well established that aza analogs of purines, pyrimidines and their nucleosides possess significant but varying potency as antineoplastic agents [1-7]. Thus, for example, 6-azacytidine is an inhibitor for orotidylic acid decarboxylase [3] and 6-azauracil inhibits the development of animal tumors [4] and human acute leukemia [5] similarly, 8-azaguanine is a highly effective anti-neoplastic agent [6] and also inhibits animal tumors [7]. 

A careful structural and theoretical study of these otho-sizsi bases and their nucleosides is, therefore, of great potential significance in attempting to understand at the molecular level the biological properties of these systems. We have, consequently, undertaken such a study [14-20]. 

The electronic significance of aza-substitution can be seen from a comparison of the structures of the unsubstituted bases with those of their aza analogs. The 6-azapyri-midines are relatively more simple than the 8-azapurines from a theoretical viewpoint since there are several reasonable tautomeric forms in the latter case vide infra). 

Pullman (ed.), Environmental Effects on Molecular Structure and Properties, 343-354. All Rights Reserved Copyright D76 by D. Reidel Publishing Company, Dordrecht-Holland 

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