Different reactivity of Sp and Rp isomers of phosphorothioate-modified oligonucleotides in a duplex structure

The presence of a stereoisomeric center at the phosphorus atom in phosphorothioate-modified oligonucleotides (PS-ONs) has been recognized as an important feature since the early stages of their development. Therefore, several studies have been conducted on the chirality of PS-ONs. In this study, we evaluated the stereo-biased chemistry of PS-ON duplexes. Depending on their absolute configurations, PS-ON duplexes were found to have significantly different and stereospecific reactivities towards simple alkylating reagent.