Sulfonate compound and fluorescent probe using the same

A sulfonate compound represented by a formula (I) below,

• where, in the formula (I), an atomic group A-O is an atomic group that forms a fluorescent compound upon cleavage of a covalent bond between the atomic group A-O and a sulfonyl group,
• one or a plurality of atomic groups B—SO3— are bonded to an atomic group A,
• B is benzene ring that is substituted by one or a plurality of electron-withdrawing groups,
• the electron-withdrawing group is at least one selected from the group consisting of an alkyl halide group (except a monochloroalkyl group, a monobromoalkyl group and a monoiodoalkyl group), a nitro group and a cyano group, and
• B may be the same or different in kind in the case where the plurality of B exist,
• the atomic group B is at least one selected from the group consisting of:
• a 2,4-dinitrophenyl group;
• a 2-nitro-(4-trifluoromethyl)phenyl group;
• a 2-nitro-4-methoxyphenyl group;
• a 4-nitro-2-methoxyphenyl group;
• a 2-nitro-4-methylphenyl group;
• a 4-nitro-2-methylphenyl group;
• a 2-nitro-4,6-dimethylphenyl group;
• a 4-nitro-2,6-dimethylphenyl group;
• a 2-nitro-4-chlorophenyl group;
• a 4-nitro-2-chlorophenyl group;
• and a 2-nitro-4-isopropylphenyl group,
• A is a formula represented by a formula (X-1) or (X-2) below,
• where, in the above formulae, each of X1, X2, Y1 and Y2 is hydrogen atom, a straight or branched alkyl group having 1 to 6 carbon atoms or a halogen, X1, X2, Y1 and Y2 may be the same or different,
• R3 is a hydrogen atom, a nitro group, a methyl group, a chloro group or a methoxy group, and
• R4 is a hydrogen atom, a nitro group, a trifluoromethyl group, a methyl group, an isopropyl group, a chloro group or a methoxy group,
• wherein a fluorescent compound formed upon cleavage of the covalent bond between the atomic group A-O and the sulfonyl group is at least one selected from the group consisting of:
• fluorescein and its derivatives.