Starting from chrysophanol and frangula-emodin the corresponding ω-hydroxy compounds, alœ-emodin and citreorosein have been prepared adopting the N-bromosuccinimide method. Partial methylation of frangulaemodin to physcion is effected most conveniently by the methyl sulphatepotassium carbonate method. Physcion can be demethylated directly to frangula-emodin by long boiling with hydrobromic acid.

A sample ofTeloschistes flavicans collected in summer 1955 was found to contain physcion and fallacinal in the proportion of 4∶1 and did not contain any appreciable amount of teloschistin. A pure sample of teloschistin has been obtained by the partial methylation of citreorosein using methyl sulphate and potassium carbonate and is found to melt at 243–44°. On oxidation with manganese dioxide it has yielded fallacinal.

2-Methylanthraquinones with the 1∶4-dihydroxy system are conveniently prepared by the persulphate oxidation of the intermediate benzoylbenzoic acids and subsequent ring closure. 2-Methylquinizarin, islandicin and cynodontin have been prepared by this method as typical examples.