摘要:
                                Two representative S-cyclonucleosides, 8,5'-anhydro-2', 3'-O-isopropylidene-8-mercaptoadenosine (3) and 8,2'-anhydro-3',5'-O-(tetraisopropyldisiloxane-1,3-diyl)-8-mercaptoguanosine  (8), were prepared in good yields by dropwise addition of one equivalent each of triphenylphosphine and DEAD in DMF into a mixture of 2',3'-O-isopropylidene-8-mercaptoadenosine (2) or 3',5'-O-(tetra-iso-propyldisiloxane-1,3-diyl)-8-mercaptoguanosine (7), respectively, in DMF. Treatment of compound 2 with two equivalents each of triphenylphosphine and DEAD in DMF afforded N-[8,5'-anhydro-2',3'-0-isopropylidene-8-mercaptopurin-6-yl]triphenylphospha-lambda5-azene (4) in 87% yield.