Synthesis of polyprenylated benzoylphloroglucinols by regioselective prenylation of phloroglucinol in an aqueous medium

Regioselective tri-C-prenylation of phloroglucinol, leading to a compound with gem-disubstitution, has been achieved with prenyl bromide in the presence of potassium hydroxide in an aqueous medium. Geranyl- and isolavandulylphloroglucinol, obtained by ortho-lithiation, were diprenylated under the same conditions. C-Benzoylation of the trialkylated derivatives using benzoyl cyanide in the presence of triethylamine afforded two natural products, grandone and kolanone, and an isomer of weddellianone A. Attemped electrophilic cyclization reactions, aimed at a biomimetic synthesis of polycyclic polyprenylated acylphloroglucinols (PPAPs), are also reported. ((c) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheirri, Germany, 2008).