Oxathiaphospholane Ring-Opening Condensation: From Oligo(Nucleoside Phosphorothioate)S To P-Chiral Analogues Of Nucleoside Polyphosphates

Among modified nucleotides and oligonucleotides, phosphorothioate analogues were the most extensively studied, both in vitro and in vivo experiments. Due to P-chirality of the phosphorus atom in a phosphorothioate moiety, the oligonucleotides synthesized using non-stereoselective standard chemical methods exist as the random mixtures of many diastereoisomers. Developed in this Laboratory, the oxathiaphospholane method of synthesis yields stereodefined oligo(deoxyribonucleoside phosphorothioate)s. Recently it was found the DBU-assisted oxathiaphospholane ring opening occurs under action of O,O-dialkyl H-phosphonates, providing so far unknown 5'-O-(alpha-thio-beta-O,O-dialkyl)hypophosphates, i.e. nucleoside diphosphates analogues with a direct P-P bond. Obtained on that way both diastereomers of adenosine 5'-O-alpha-thiohypophosphate were chromatographically separated. The fast-eluting P-diastereomer was a substrate for pyruvate kinase-assisted phosphorylation and yielded diastereomerically pure alpha,beta-hypophosphate analogue of ATP alpha S. Both isomers were found to act as inhibitors of T7 RNA polymerase.