What is described is a compound of formula IwhereinR is a linear alkyl of 1 to 12 carbons, or a linear alkenyl or alkynyl of 2 to 12 carbons；L is a linear alkylene or alkenylene of 5 to 18 carbons；X is —CO—O— or —O—CO—；Y is S or O；R1 is a linear or branched alkylene consisting of 1 to 6 carbons； andR2 and R3 are the same or different, consisting of a hydrogen or a linear or branched alkyl consisting of 1 to 6 carbons； andn is 1-6；or a salt, a solvate, or a pharmaceutical formulation thereof.
