Summary
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.
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Rajagopalan, T.R., Seshadri, T.R. Synthesis of citreorosein and alŒ-emodin. Proc. Indian Acad. Sci. 44, 418–422 (1956). https://doi.org/10.1007/BF03046096
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DOI: https://doi.org/10.1007/BF03046096