f 3 to 24 carbon atoms saturated or unsaturated, with the proviso that at least one of R1, R2 and R3 is an acyl group derived from a fatty acid, or to a compound having the formula (2): w . . . xyNHCH2 CH2 OR5, in which w is a nucleic acid, x is a peptide or amino acid, y is a linker having a chain length equivalent to 1 to 20 carbon atoms or absent, R5 is an acyl group derived from a fatty acid h