SYNTHESIS OF SOME 1,3,6-TRIOXYGENATED ISOPENTENYLATED XANTHONES - CONSTITUTION OF GARCINONE-A

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