Compound for Use in Enzymatic Reaction and Mass Spectrometry Method

A compound represented by the general formula (1):

• or the general formula (2):
• or the general formula (3):
• or the general formula (4):
• wherein in the general formulae (1), (2), (3), and (4),
• R1, R2, R3, and R4 may be the same as or different from each other and each represents an alkyl group, an aryl group, a cycloalkyl group, or a heterocyclic group having no substituent or having a substituent W, wherein W represents a C1 to 10 saturated or unsaturated hydrocarbon group, an aryl group, a heterocyclyl group, an alkoxy group, a fluoroalkyl group, an acyl group, an ester group, a hydroxyl group, an amino group, an amide group, a carboxyl group, a sulfonyl group, a nitro group, a cyano group, a sulfenyl group, a sulfo group, a mercapto group, a silyl group, or a halogen group,
• R5 represents an aryl group, a cycloalkyl group, or a heterocyclic group not having a substituent other than an —X—Y group, a —Y group, and an —X—H group or having a substituent W other than an —X—Y group, a —Y group, and an —X—H group,
• A1 and A2 may be the same as or different from each other and each represents an alkyl group having no substituent or having the substituent W, and
• X represents a sulfur atom or an oxygen atom, and
• wherein the general formulae (1) and (2), Y is a saccharide,
• or a salt thereof.