What is described is a compound of formula I
consisting of a compound in which R1 is a branched chain alkyl consisting of 10 to 31 carbons; R2 is a linear alkyl, alkenyl, or alkynyl consisting of 2 to 20 carbons; L1 and L2 are the same or different, each a linear alkylene of 1 to 20 carbons or a linear alkenylene of 2 to 20 carbons; X1 is S or O; R3 is a linear or branched alkylene consisting of 1 to 6 carbons; and R4 and R5 are the same or different, each a hydrogen or a linear or branched alkyl consisting of 1 to 6 carbons; or a pharmaceutically acceptable salt thereof.
所述的是式 I 的化合物
其中 R1 是由 10 至 31 个碳原子组成的支链烷基;R2 是由 2 至 20 个碳原子组成的直链烷基、烯基或炔基;L1 和
L2 相同或不同,各自是 1 至 20 个碳原子的直链亚烷基或 2 至 20 个碳原子的直链烯基;X1 是 S 或 O;R3 是由 1 至 6 个碳原子组成的直链或支链亚烷基;R4 和 R5 相同或不同,各自是氢或由 1 至 6 个碳原子组成的直链或支链烷基;或其药学上可接受的盐。