Synthesis and duplex stabilization of oligonucleotides consisting of isonucleosides

Novel oligonucleotide analogues built from isonucleosides were synthesized by the phosphoramidite approach on an automated DNA synthesizer. The phosph oramidite building blocks were synthesized by phosphitylation of the corres ponding protected isonucleosides. The oligonucleotide analogues C - G conta ining the isonucleoside 1-3 were studied with respect to their hybridizatio n properties and enzymatic stability. The oligomers bearing an isonucleosid e at the end of the strands all proved stable towards snake-venom phosphodi esterase, but only the oligomers D-G exhibit acceptable duplex stability wh en hybridized with complementary d(A(14)).