Abstract
For studies of the conformation of nucleosides around the glycosyl linkages, the carbonbridged cycloadenosines, 8, 6'-cyclo-6'-deoxyallofuranosyladenine and its 5'-epimer, were synthesized by the following route. Treatment of N6-benzoyl-2', 3'-O-isopropylideneadenosine 5'-aldehyde (1) with dimethyloxosulfonium methylide afforded the 5', 6'-anhydrohexofuranosyladenine (2), which was treated with thiophenoxide to give the diastereomeric 6'-phenylthio derivatives (4). Photoirradiation of 4 followed by 5'-O-acetylation afforded 5'-O-acetyl-8, 6'-cyclo-6'-deoxy-hexofuranosyladenine derivatives (6b, 7b). Attempted synthesis of a 8, 7'-cyclo-heptofuranosyl derivative by way of photolysis of a 7'-phenylthio-heptofuranosyladenine resulted in the formation of 5', 6', 7'-trideoxy-2', 3'-O-isopropylidene-β-D-ribo-heptofuranosyladenine (11). The nature of the circular dichroism spectra of 6 and 7 is discussed.
