A compound having superior solubility and suitable for a liposome contrast medium selective for a lesion such as vascular diseases is provided which is represented by the following general formula (I) wherein R1 to R3 represent an alkyl group or alkenyl group X1 and X2 represent a single bond, &mdashO&mdash, or &mdashN(Z1)- (Z1 represents hydrogen atom, or an alkyl group) X3 to X6 represent &mdashO&mdash, or &mdashN(Z2)- (Z2 represents hydrogen atom, or an alkyl group) n represents an integer of 1 to 10 and L represents a divalent bridging group constituted by atoms selected from the group consisting of carbon atom, hydrogen atom, oxygen atom, nitrogen atom, fluorine atom and sulfur atom.
