EFFICIENT INTRODUCTION OF PHOSPHOROTHIOATES INTO RNA OLIGONUCLEOTIDESBY 3-ETHOXY-1,2,4-DITHIAZOLINE-5-ONE (EDITH)

We recently reported on the use of 1,2,4-dithiazolidine-3,5-dione (Dts NH) and 3-ethoxy-1,2,4-dithiazoline-5-one (EDITH) as effective sulfuri zing reagents for the preparation of phosphorothioate-containing oligo deoxyribonucleotides [Xu et al, (1996) Nucleic Acids Res., 24, 1602-16 07]. One challenge in automated solid-phase synthesis of phosphorothio ate-containing RNA is to develop sulfurization reagents that are effec tive in the presence of bulky 2'-OH protecting groups. The present stu dy demonstrates that EDITH is exceedingly effective at low concentrati ons (0.05 M) and short reaction times (2 min) for the automated synthe sis of oligoribonucleotides.