Xanthones, prenyl derivs

The phenolics include anthocyanins, anthraquinones, benzofurans, chromones, chromenes, coumarins, flavonoids, isoflavonoids, lignans, phenolic acids, phenylpropanoids, quinones, stilbenes and xanthones. Some phenolics can be very complex in structure through additional substitution or polymerization of simpler entities. Thus xanthones can be prenylated and flavonoids, lignans and other phenolics can be glycosylated. Condensed tannins involve the polymerization of procyaninidin or prodelphinidin monomers and hydrolysable tannins involve gallic acid residues esterified with monosaccharides. As detailed in this review, representatives of some major classes of plant-derived phenolics are potent protein kinase inhibitors. 

The isomeric products of the xanthone synthases are the precursors of the majority of plant xanthones (77). This class of secondary metabolites also includes prenylated compounds with high pharmaceutical potential. Gambogic acid is a bridged polycyclic derivative that induces apoptosis independent of the cell cycle through a novel mechanism of caspase activation (22). Rubraxanthone inhibits methicillin-resistant strains of Staphylococcus aureus 23). Its activity compares to that of the antibiotic vancomycin. Bioactive complex benzophenone derivatives may serve as potential lead compounds for designing drugs. Synthetic approaches to these fascinating structures have recently been developed 24,25). 

Recently, a study on the synthesis of novel natural secondary allylic alcohol derivatives was carried out by Helesbeux et al. [64]. The photooxygenation-reduction sequence was apphed in the prenylated xanthone series also... 

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