Stereocontrolled solid-phase synthesis of phosphorothioate oligoribonucleotides using
Yohei Nukaga1, Kohei Yamada, Toshihiko Ogata
1Department of Medical Genome Sciences, Graduate School of Frontier Sciences, The University of Tokyo, Bioscience Building 702, 5-1-5 Kashiwanoha, Kashiwa, Chiba 277-8562, Japan.
Abstract:
A method for the synthesis of P-stereodefined phosphorothioate oligoribonucleotides (PS-ORNs) was developed. PS-ORNs of mixed sequence (up to 12mers) were successfully synthesized by this method with sufficient coupling efficiency (94-99%) and diastereoselectivity (≥98:2). The coupling efficiency was greatly improved by the use of 2-cyanoethoxymethyl (CEM) groups in place of the conventional TBS groups for the 2'-O-protection of nucleoside 3'-O-oxazaphospholidine monomers. The resultant diastereopure PS-ORNs allowed us to clearly demonstrate that an ORN containing an all-(Rp)-PS-backbone stabilizes its duplex with the complementary ORN, whereas its all-(Sp)-counterpart has a destabilizing effect.
