2′-O-HYDROXYALKOXYMETHYLRIBIBONUCLEOSIDE AND THEIR INCORPORATION INTO OLIGORIBONUCLEOTIDES

A simple and efficient method for the preparation of pyrimidine 2′-O-hydroxyethoxymethylribonucleosides and 2′-O-hydmxypropoxymethylribonucleosides has been developed. These modified nucleosides were incorporated into oligoribonucleotides, which were shown to form stable RNA/RNA duplexes. The effect of 2′-O-modification in the antisense and sense strands of small interference RNA was evaluated in multi-drug resistant NIH 3T3 cells

A large-scale chemical modification screen identifies design rules to generate siRNAs with high activity, high stability and low toxicity

The use of chemically synthesized short interfering RNAs (siRNAs) is currently the method of choice to manipulate gene expression in mammalian cell culture, yet improvements of siRNA design is expectably required for successful application in vivo. Several studies have aimed at improving siRNA performance through the introduction of chemical modifications but a direct comparison of these results is difficult. We have directly compared the effect of 21 types of chemical modifications on siRNA activity and toxicity in a total of 2160 siRNA duplexes. We demonstrate that siRNA activity is primarily enhanced by favouring the incorporation of the intended antisense strand during RNA-induced silencing complex (RISC) loading by modulation of siRNA thermodynamic asymmetry and engineering of siRNA 3′-overhangs. Collectively, our results provide unique insights into the tolerance for chemical modifications and provide a simple guide to successful chemical modification of siRNAs with improved activity, stability and low toxicity

Phosphoramidite building blocks for efficient incorporation of 2 '-O-aminoethoxy(and propoxy)methyl nucleosides into oligonucleotides

A simple and efficient method for the preparation of eight phosphoramidite building blocks for incorporation of 2'-O-(2-aminoethoxymethyl)ribonucleosides and 2'-O-(3-aminopropoxymethyl)ribonucleosides into synthetic oligonucleotides has been developed. The synthetic routes are maximally convergent and provide sufficient amounts of phosphoramidites for several solid-phase synthesis coupling reactions. Using acyclic derivatives 17a,b the overall yields of phosphoramidites 2 and 3 were increased up to 50% for pyrimidine nucleosides and up to 30% for purine derivatives with substantial decrease of total reaction steps. The 2'-O-substituent was found to be stable during oligonucleotide synthesis. The resulting oligonucleotides are of particular interest for post-synthetic functionalization and conjugation. (C) 2008 Elsevier Ltd. All rights reserved.status: publishe

Studies on disaccharide nucleoside synthesis

status: publishe