The invention relates to compositions containing compounds of formula I:and pharmaceutically acceptable salts thereof, wherein R, R1, R2, R3, and n are defined in the detailed description and claims. In addition, the present invention relates to novel formulations containing compounds of formula I for improved delivery of nucleic acids such as siRNA to the cytoplasm of target cells. In particular embodiments these formulations comprise compounds of formula I, phospholipids, cholesterol, and pegylated lipids. The present invention also relates to methods of manufacturing and using such compounds and compositions.
