6-{(2R,3R,4R,5R)-5-[6-(Trityl-amino)-purin-9-yl]-4-trityloxy-2-trityloxymethyl-tetrahydro-furan-3-yloxy}-hexanoic acid

6-{(2R,3R,4R,5R)-5-[6-(Trityl-amino)-purin-9-yl]-4-trityloxy-2-trityloxymethyl-tetrahydro-furan-3-yloxy}-hexanoic acid 2-cyano-ethyl ester