(E)-4-(3-Methoxy-4-hydroxyphenyl)-4-oxo-buten-2-oic acid (E)-4-(4-Hydroxy-3-methoxyphenyl)-4-oxo-2-butenoic acid 2-Butenoic acid, 4-(4-hydroxy-3-methoxyphenyl)-4-oxo-, (E)- 86690-98-4