4-methyltropolone
4-(4-dimethylamino-trans-styryl)-tropolone
2-(3,4-dimethoxy-trans-styryl)-6-hydroxy-7-oxo-cyclohepta-1,3,5-trienecarboxylic acid
[2-(4-ethoxycarbonyl-phenylazo)-7-carboxy-6-hydroxy-5-oxo-cyclohepta-1,3,6-trienyl]-acetic acid
[7-carboxy-6-hydroxy-5-oxo-2-(4-sulfamoyl-phenylazo)-cyclohepta-1,3,6-trienyl]-acetic acid