SYNTHESIS AND NMR CONFORMATIONAL STUDIES OF THE RIBOSIDE ANALOG OF CYANOTHYMIDINE - CONFORMATIONAL CHANGE OF THE NUCLEOSIDE WITH THE SOLVENT

We report a procedure for the preparation of -acetyl-3'-C-cyano-3'-des oxy-beta-D-ribofuranosyl) thymine 11 and 3'-C-cyano-3'-deoxy-2',3'-did ehydrothymidine 12 as pure beta-anomers from thymine and 1,2,5-tri-O-a cetyl-3-C-cyanoribofuranose. The averaged conformation of nucleoside 1 1, in CDCl3 and DMSO is established by H-1 and C-13 NMR spectroscopy. The method used involves the determination of H-1-H-1 and H-1-C-13 cou pling constants by 1D and 2D methods and the use of n.O.e. experiments . The results suggest changes in the conformation of the ribose moiety and the conformation around the glicosidic bond with the solvent.