Protected ribonucleotides

Hydroxyl protection. Ribonucleotides protected as the sulfonyl derivatives can be cleaved under aprotic conditions on treatment with DBU involving a P-elimination process. 

As in the deoxyribonucleotide series, gel filtration has been used to separate larger blocks after condensation, an example being the separation of the protected nonamer CpGpUpCpCpApCpCpA from a hex-amer and a trimer.112 However, the lower solubility of protected oligo(ribonucleotide) blocks demands the use of an alkylated dextran... 

The mutagenic ribonucleotide rPTP (87) has been used in an in vitro retroviral replication model. After four rounds of replication the mutation frequency was raised to 3.8 x 10 per nucleotide, with C U and U C mutations observed. It was suggested that such an analogue could induce mutations in a retroviral target beyond its error threshold. The tricyclic cytosine analogues phenoxazine and 9-(2-aminoethoxy)-phenoxazine (g-clamp, see (141)) have been incorporated into ODNs to study their effect with exonuclease. It was found that a single substitution at the 3 -terminus afforded complete protection of the ODN with snake venom phosphodiesterase. ... 

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