“…The 2-azapurines, such as 2-azaadenine and 2-azahypoxanthine, have also long been known to inhibit the growth of both microbial and mammalian cells. − Although the physical properties of these nucleosides have been studied, very few were incorporated in oligonucleotides . Recently, 2-aza-2‘-deoxyadenosine ( 3 ) was synthesized by our laboratory, and its behavior within oligonucleotide duplexes was studied. , In continuation of the work on 2-azapurine nucleosides and oligonucleotides and as the result of the unusual base pairing properties of 3 , the related 7-deaza-2,8-diazapurine (7 H -pyrazolo[3,4- d ][1,2,3]triazine) system is now investigated (purine numbering is used throughout the general part).…”