Synthesis of some 1,3,6-trioxygenated isopentenylated xanthones: Constitution of garcinone A

The reaction of l,3-dihydroxy-6-methoxy- and 1,3,6-trihydroxy-xanthone with 1-bromo3-methylbut-2-ene in presence of methanolic sodium methoxide, to give corresponding 3-methylbut-2enylated xanthones, is described. Synthesis of 1,3,6-trihydroxy-2,4-bis(3-methylbut-2-enyl)-9H- xanthen-9-one, designed as garcinone A and reported as a natural product from the fruit-hulls of Garcinia mangostana (Guttiferae), has also been achieved. However synthetic xanthone is found to be different from natural garcinone A, therefore its constitution needs reinvestigation.