Synthesis of oligonucleotides using the 2-(levulinyloxymethyl)-5-nitrobenzoyl group for the 5'-position of nucleoside 3'-H-phosphonate and -H-phosphonothioate derivatives

Synthetic studies on phosphodiester, phosphorothioate, and phosphorodithioate-linked oligonucleotides in terms of 2-(levulinyloxymethyl)-5-nitrobenzoyl (LMNBz) group as the base-labile protecting group for the 5'-hydroxyl groups of nucleoside 3'-H-phosphonate and -H-phosphonothioate derivatives, are described.