Novel lipid‐oligonucleotide conjugates containing long‐chain sulfonyl phosphoramidate groups: Synthesis and biological properties

New lipid conjugates of DNA and RNA incorporating one to four [(4‐dodecylphenyl)sulfonyl]phosphoramidate or (hexadecylsulfonyl)phosphoramidate groups at internucleotidic positions near the 3′ or 5′‐end were synthesized and characterized. Low cytotoxicity of the conjugates and their ability to be taken up into cells without transfection agents were demonstrated. Lipidconjugated siRNAs targeting repulsive guidance molecules a (RGMa) have shown a comparable gene silencing activity in PK‐59 cells to unmodified control siRNA when delivered into the cells via Lipofectamine mediated transfection.