5,12-dihydroxy-3,4-dihydro-1H-tetracene-2,6,11-trione

2-(3-methylbut-2-enyl)benzene-1,4-diol

ethyl (Z)-3-(2,5-dihydroxyphenyl)sulfanylbut-2-enoate

Ethyl-(E)-β-(2,5-dihydroxyphenylthio)-crotonat

ethyl 3-(3,6-dioxocyclohexa-1,4-dien-1-yl)sulfanylbut-2-enoate