the group consisting of a cholesteryl radical and a radical selected from the group consisting of the formulas ##STR14## in which P is a radical selected from the group consisting of an oxygen atom, a sulfur atom, --Cd He --, where d and e are the same as above, and an N-alkylamino radical, v is an integer of from 0 to 12, E is a radical selected from the group consisting of --CH2 --CH2 --, --CH2