title: Comparative study by circular dichroism of the conformation of deazapurine nucleosides and that of common purine nucleosides.
abstract: Purine nucleoside analogs modified by replacement of the nitrogen atom at the 3 position by a CH group give a characteristic circular dichroism curve that is not substantially modified by chemical substitution at the 8 position. Since it is rather well established that 8-substituted purine nucleosides are predominantly in the syn conformation in aqueous solution, it follows that the 3-deazapurine nucleosides, whether substituted at position 8 or not, also favor the syn conformation. These data are in sharp contrast to the circular dichroism data obtained on 8-halogenated and 8-alkylated derivatives of adenosine and guanosine, which give circular dichroism profiles substantially different from those obtained on the parent compounds. Certain purine-nucleoside-utilizing enzymes fail to interact effectively with either the unsubstituted 3-deaza analogs or the 8-substituted derivatives of adenosine and guanosine. The hypothesis recently given that the inactivity of the 8-substituted derivatives springs from their syn-conformational preference is tentatively accepted to explain the inactivity of the 3-deaza analogs.
mesh_terms: D000241:Adenosine / Q000031:analogs & derivatives; D001562:Benzimidazoles; D002942:Circular Dichroism; D008968:Molecular Conformation; D011684:Purine Nucleosides; D012263:Ribonucleosides; D013056:Spectrophotometry, Ultraviolet; D013329:Structure-Activity Relationship
chemical_list: D001562:Benzimidazoles; D011684:Purine Nucleosides; D012263:Ribonucleosides; D000241:Adenosine