Lactone compounds

The invention relates to a lactone compound. The technical problem to be solved is to provide a lactone compound with excellent water stability. The lactone compound is represented by formula (I). In formula (I), R1 and R2 each independently represent a substituent group that does not have a dissociative protons having a Hammett substituent constant [sigma] p value of-0.90 to-0.03 (inclusive). And R3 represents a hydrogen atom or a substituent group that does not have a dissociative proton having a Hammett substituent constant [sigma] p value of-0.90 to-0.03 (inclusive). Y represents a substituent, and n represents an integer of 1-4. When n is an integer from 2 to 4, the two or more Y groups may each be the same substituent or different substituents. 本发明涉及内酯化合物，所要解决的技术问题在于提供一种水稳定性优异的内酯化合物。内酯化合物由下述式(I)表示。在下述式(I)中，R1及R2分别独立地表示不具有哈米特取代基常数σp值为-0.90以上-0.03以下的解离性质子的取代基。R3表示不具有哈米特取代基常数σp值为-0.90以上-0.03以下的解离性质子的取代基或氢原子。Y表示取代基，n表示1～4的整数。在n为2～4的整数的情况下，2个以上Y分别可以是相同的取代基，也可以是不同的取代基。