Polyprenylated benzophenones

Ito, C., Itoigawa, M., Miyamoto, Y., Onoda, S., Rao, K.S., Mukainaka, T., Tokuda, H., Nishino, H. and Furukawa, H. (2003a) Polyprenylated benzophenones from Garcinia assugu and their potential cancer chemopreventive activities. Journal of Natural Products 66(2), 206-209. 

Prenylated natural products of close similarity to hyperforin 10 were also reported from other species of the Guttiferae family. Biogenetically they are classified as polyprenylated benzophenones, however many of them bear a bicyclononane ring system as with hyperforin 10. Xanthochymol 27, which is identical with guttiferone E, was isolated from... 

Historically, reviews of benzophenones were included as small sections with the biogenetically related xanthones. Previous reviews include Bennett and Lee [1] who discussed the distribution and isolation of 20 benzophenones included in a review focused on xanthones. They also discussed the biosynthetic relationships between xanthones and benzophenones. Kumar and Baslas [2] summarized the chemical composition, medical importance, and biologically active benzophenones, biflavonoids, and xanthones isolated from Garcinia species. Two reviews by Waterman focused on the chemotaxonomic significance of benzophenones, along with biflavonoids and xanthones, of ten African Garcinia species [3,4], Locksley and Murray [5] discussed the distribution of thirteen benzophenones in higher plants and Sultanbawa [6] included five benzophenones in a review on xanthonoids from tropical plants. Sultanbawa also discussed the biosynthesis of benzophenones and xanthones. Erdelmeier et al. [7] discussed 20 polyprenylated benzophenones in a chapter on the various properties of St. John s Wort Hypericum perforatum). 

The most common polyprenylated benzophenones have a bicyclo[3.3. l]nonane B/C-ring system. Approximately 38 bicyclo[3.3.1]nonane benzophenones have been isolated. A typical bicyclo[3.3.1]nonane benzophenone is xanthochymol (138), which is discussed in detail below. 

The floral resin of twelve Clusia species has yielded at least fourteen (66, 79-80, 82, 85, 87-89, 93-94, 96, 114-115, 122) bioactive bicyclo[3.3.1]nonane polyprenylated benzophenones. These compounds have the isoprenyl and benzoyl residues attached at different positions on the bicyclo[3.3.1]nonane ring [58,59,68,73,102]. In addition, the floral resin is used by pollinating bees for nest construction [77]. 

Benzophenone synthase (BPS) and biphenyl synthase (BIS) catalyze the formation of the same linear tetraketide from benzoyl-CoA and three molecules of malonyl-CoA. However, BPS cyclizes this intermediate via intramolecular C6-+C1 Claisen condensation, whereas BIS uses intramolecular C2— C7 aldol condensation. Benzophenone derivatives include polyprenylated polycyclic compounds with hi pharmaceutical potential. Biphenyl derivatives are the phytoalexins of the economically important Maloideae. 

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