Cationic cholesteryl derivatives containing cyclic polar groups

A method transfecting nucleic acids into cells, the method comprising:

• contacting said cells with a nucleic acid:lipid complex, wherein the lipid comprises a compound having the structure:
• X—R2—R1-Cholesteryl, wherein
• R1 is a direct bond to the 3 carbon of cholesteryl or a linker bond
• R2 is a direct bond, a branched or linear alkylene or alkenylene chain of 1 to 10 carbons in length, a C3-C7 cycloalkylene, or a phenylene;
• X is a 4-7-membered nitrogen-containing cyclic structure;
• and
• X is linked to the R2 spacer via a carbon atom of the nitrogen-containing cyclic structure or via a nitrogen atom of the cyclic structure.

A method for transfecting nucleic acids into cells, the method comprising:

• contacting said cells with a nucleic acid:lipid complex, wherein the complex comprises a nucleic acid and a compound having the structure:
• X—R2—R1—O-Cholesteryl, wherein
• R1 is a linker bond —NH—C—, —C—, or O—C—;
• R2 is a direct bond, a branched or linear alkylene or alkenylene chain of 1 to 10 carbons in length, a C3-C7 cycloalkylene, or a phenylene;
• X is a 4-7-membered nitrogen-containing cyclic structure;
• X is linked to the R2 spacer via a carbon atom of the nitrogen-containing cyclic structure or via a nitrogen atom of the cyclic structure;
• and
• X further comprises a heteroatom selected from the group consisting of S, O, and NR3, wherein R3 is —H, —CH3, —C2H5, —CH2(CH2)ZOH or —CH2(CH2)ZSH, wherein Z is 0-3.