Incorporation of modified nucleosides with a flexible universallinker is of great value for post-synthetic modification of nucleicacids. Thus, C8-alkynyl- and alkylamino substituted 2′-deoxyguanosines were synthesized for the first time and incorporated into short oligonucleotide sequences. The preference for syn conformation of these C8-substituted 2′-deoxyguanosines and the stability of the duplexes