Abstract
Treatment of 2', 3'-O-isopropylidene-5'-oxo-8, 5'-cycloadenosine with dimethyloxosulfonium methylide followed by hydrogenation afforded the diastereomeric pairs of 5'-methyl-5'-deoxy-8, 5'-cycloadenosine and 5'-hydroxymethyl-5'-deoxy-8, 5'-cycloadenosine. The configurations at the 5'-positions of these 8, 5'-cycloadenosines were determined by nuclear magnetic resonance (NMR) measurements. The Wittig reactions of the 5'-oxo-8, 5'-cycloadenosine with methoxymethylenetriphenylphosphorane, methylthiomethylenetriphenylphosphorane, and ethyl (dimethylsulfuranylidene) acetate afforded the corresponding 5'-substituted derivatives. The action of ethoxycarbonylmethylenetriphenylphosphorane with the 5'-oxo-8, 5'-cycloadenosine afforded the 5'-ethoxycarbonylmethylene-8, 5'-cycloadenosine, which was converted to 5'-hydroxyethyl-5'-deoxy-8, 5'-cycloadenosine by reduction with LiBH4 followed by deacetonation. The 5'(R)- and 5'(S)-diastereomers of the 5'-hydroxyethyl derivative were separated and identified by NMR analysis. The circular dichroism (CD) spectra of the 5'-substituted-8, 5'-cycloadenosines showed that the diastereomers having the substituent at the trans-gauche position around the C4'-C5' bond gave strong negative CD bonds, whereas the diastereomers with the 5'-substitutent at the gauche-trans position exhibited positive bands.
