Synthesis of 2',3'-Didehydro-2',3'-dideoxynucleosides by Reaction of 5'-Protected Nucleoside 2',3'-Dimesylates with Telluride Dianion: A General Route from Cis Vicinal Diols to Olefins

2',3'-Dimesylates of 5'-protected nucleosides are converted into the corresponding 2',3'-didehydro-2',3'-dideoxy compounds by treatment with telluride dianion in the form of the sodium or lithium salt. The method is well-suited to the preparation of unsaturated nucleosides that can be converted into compounds that are believed to be useful in the treatment of AIDS. The deoxygenation is general for vicinal dimesylates that have, or may adopt, a synperiplanar conformation. With straight chain compounds the reaction is stereospecific. In some cases, similar, but slower, deoxygenations can be performed with selenide dianion.