The 7-substituents of 7-deazapurines have considerable steric freedom within the major groove of DNA and stabilize the oligonucleotide duplex structure1. Therefore, the 7-position of 7-deazapurines is an ideal position for the fuctionalization of DNA with reporter groups. This investigation reports on the synthesis of 7-substituted 7-deazaguanosine and 7-deaza- 8-azaguanosines, their incorporation into oligonucleotides, and the stability of ...