Purpurogallin (1,7,8,9-Tetrahydroxy-2H-benzo[7]annulen-2-one) is a benzotropolone having a dienic system and is known to inhibits TLR1/TLR2 activation pathway. We have recently described the easy green synthesis of purpurogallin from pyrogallol catalyzed by a copper complex or by vegetable oxidases.

The purpurogalline was acetylated and the tetraacetate derivative thus obtained was engaged in a Diels Alder reaction with various dienophiles (benzoquinone, maleic anhydride, ethylmaleimide, azodicarboxylate, etc.). The results obtained will be presented and discussed. Theoretical calculations using DFT have been performed.