Synthesis, binding, nuclease resistance and cellular uptake properties of 2′-O-acetalester-modified oligonucleotides containing cationic groups

Abstract

We report on the synthesis and properties of oligonucleotides (ONs) with 2′-O-acetalester modifications containing cationic side chains in a prodrug-like approach. In the aim to improve cell penetration and nuclease resistance, various different amino- or guanidino-acetalester were grafted to 2′-OH of uridine and the corresponding phosphoramidites were incorporated into ONs. Introduction of 2′-O-(2-aminomethyl-2-ethyl)butyryloxymethyl (AMEBuOM) modification into 2′-OMe ONs leads to high resistance towards enzymatic degradation and to destabilization of duplexes with complementary RNA strand. Spontaneous uptake experiments of a twelve-mer containing ten 2′-O-AMEBuOM-U units into A673 cells showed moderate internalization of ON within the cells whereas substantial internalization of the corresponding lipophilic 2′-O-pivaloyloxymethyl ON was observed for the first time.