The synthesis of phosphoramidites (2 and 3) derived from hypoxanthine
and isoguanine N-7-2'-deoxyribonucleosides is described. Solid-phase s
ynthesis furnishes oligonucleotides containing N-7-glycosylated purine
s. New base pairs between purine N-7- and N(z)9-nucleosides are propos
ed.