A compound (A) is represented by the formula (1):
wherein R1 is a hydrogen atom or an alkali metal atom, R2 is a hydrogen atom or an alkali metal atom, R3 is a hydrogen atom or a methyl group, Z is a divalent or trivalent organic group, and the lines consisting of a solid line and a broken line bonded to Z represent a single bond or a double bond.
化合物 (A) 由式 (1) 表示:
其中 R1 是氢原子或碱
金属原子,R2 是氢原子或碱
金属原子,R3 是氢原子或甲基,Z 是二价或三价有机基团,与 Z 键合的由实线和折线组成的线代表单键或双键。