Abstract: A diarylethene compound represented by formula (I) wherein, Sg is a monovalent sugar residue formed by removing one hydroxyl group from a sugar compound or a monovalent protected sugar residue formed by removing one hydroxyl group from a sugar compound in which one or more other hydroxyl groups are protected, and wherein the sugar is selected from the group consisting of a six-membered ring sugar, a five-membered ring sugar, cyclitol, and oligosaccharides containing a six-membered ring sugar, a five-membered ring sugar, or cyclitol; U is —(CH2)n—, —CH2—U?—, or —C(?O)— wherein n is an integer of 1 to 5, U? is a C2-C10 branched alkylene group binding to Ar); and Ar is a group represented by formula (A1) or (A2); wherein, X is S, SO2, NR3 in which R3 is a C1-C3 alkyl group, or O, R is C1-C4 alkyl group, R1 and R2 are independently a C1-C3 alkyl group, a is 0 or 1, b is an integer of 0-3, and * represents a bond with U; Y is a hydrogen atom or a halogen atom; and m is an integer of 3 to 5.

Abstract: A diarylethene compound having high water-solubility is provided, and the compound is a diarylethene compound of formula (I) wherein, Sg is a monovalent sugar-type residue consisting of a sugar-type compound (in which some of hydroxyl groups may be protected) selected from a group consisting of a six-membered ring sugar, a five-membered ring sugar, cyclitol and oligosaccharides containing a six-membered ring sugar, a five-membered ring sugar, or cyclitol and excluding an hydroxyl group; U is —(CH2)n-, —CH2—U?—, or —C(?O)— (wherein, n is an integer of 1 to 5, U? is a C1-C10 alkyl group binding to Ar); and Ar is a group represented by formula (A1) or (A2); wherein, X is S, SO2, NR3 (R3 is a C1-C3 alkyl group) or O, R is C1-C4 alkyl group, R1 and R2 are independently a C1-C3 alkyl group, a is 0 or 1, b is an integer of 0-3, and * represents a bond with U); Y is a hydrogen atom or a halogen atom; m is an integer of 5-7.