Prenylated benzophenones

Chattopadhyay, S.K. and Kumar, S. (2006) Identification and quantification of two biologically active polyiso-prenylated benzophenones, xanthochymol and isoxanthochymol, in Garcinia species using liquid chromatography-tandem mass spectrometry. Journal of Chromatography B 844(1), 67-83. 

Rama Rao, A.V., Venkataswamy, C. and Yemul, S.S. (1 980) Xanthochymol and isoxanthochymol two polyiso-prenylated benzophenones from Carcinia xanthoxhymus. Indian Journal of Chemistry 19, 627-633. 

In contrast to prenylated benzophenones, simple benzophenones are of rare occurrence in the Clusiaceae family and so far only few examples have been described in the literature [83]. 

It is very interesting to note the high percent of prenylated benzophenone derivatives in some natural sources. Floral resins, latex, leaves, and fruits can contain up to 70 % of these compounds [19,20]. 

All NMR data of myrtiaphenone B (13) were in agreement with the structural characteristics of prenylated benzophenones. The resonances at 8 6.40 and 5.32 shared a J constant of 10 Hz, typical of a cis double bond, and a gem-dimethyl group indicated the presence of a chromene ring. Myrtiaphenones are very closely related from a structural point of view. Myrtiaphenone A can be easily converted in myrtiaphenone B by cyclo dehydrogenation with DDQ. 

Fuller et al., following anti-HIV bioassay-guided fractionation isolated four new prenylated benzophenones, vismiaphenones D-G (7-10), from extracts of leaves of V. cayennensis [25]. All these compounds showed to be very similar to vismiaphenones A-B (4, 5) and myitiaphenones A-B... 

Boyd et al. in a bio-assay oriented study reported that the anti-HIV activity exhibited by extracts of some Guttiferae species was attributed to a series of prenylated benzophenone derivates. 

Tanaka N, Takaishi Y, Shikishima Y, Nakanishi Y, Bastow K, Lee KH, Honda G, Ito M, Takeda Y, Kodzhimatov OK, Ashurmetov O (2004) Prenylated benzophenones and xanthones from Hypericum scabrum. J Nat Prod 67(11) 1870-1875... 

Benzophenones and xanthones have the C6-C1-C6 structure. The basic structure of benzophenone is a diphenyl ketone, and that of xanthone is a lO-oxy-10/7-9-oxaanthracene. More than 500 xanthones are currently known to exist in nature, and approximately 50 of them are found in the mangosteen with prenyl substituents. 

Turek, T.C., Gaon, L, Distefano, M.D., and Strickland, C.L. (2001). Synthesis of farnesyl diphosphate analogues containing ether-linked photoactive benzophenones and their application in studies of protein prenyltransferases. J Org Chem 66 3253-3264. Turek-Etienne, T.C., Strickland, C.L., and Distefano, M.D. (2003). Biochemical and structural studies with prenyl diphosphate analogues provide insights into isoprenoid recognition by protein farnesyl transferase. Biochemistry 42 3716-3724. 

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). 

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... 

PBDs seem to be derivatives of maclurin or another benzophenone derivative modified in the A ring by intervention of prenyl groups. B ring can be unsubstituted or contain up to 2 phenolic groups. 

It remains unclear whether the basic 13-carbon benzophenone is constructed (from the shikimate and acetate pathways) and then prenylated and cyclized or the B-ring is derived from phloroglucinol and later the 7-membered carbon substructure (A-ring) is added. Given the structural diversity of benzophenones, their biosynthesis is suggestive of multiple pathways. Further research is needed to fully understand the biosynthesis of benzophenones. 

Benzophenones and xanthones are known to co-occur in the Clusiaceae [1], and the garciduols (74, 75, 84) are three benzophenone-xanthone dimers [27,64]. The cudraphenones (33, 37, 42, 37), a group of benzophenones isolated from the Moraceae family, are prenylated on the A- and B-rings [47], These are the only four compounds that are prenylated on both the A- and B-rings. 

Ten benzophenone glycosides, nine O-glycosides (56-58, 60, 62, 67-68, 71-72) and one C-glycoside (61) have been isolated from five different plant species. None of these are prenylated, and the glycoside substituent is attached to either the A- or B-ring [39,54-57,60,63],... 

Xanthochymol (138), to our knowledge, is the only benzophenone analyzed, in detail, for its electron impact MS fragmentation behavior [110]. Reported MS losses for benzophenones include an m/z 105 (CsHs-CO4) for a unsubstituted phenyl ketone A-ring [44,65], m/z 137 (G,H O3-CO4) for a 3,4-dihydroxybenzophenone moiety, and m/z 68 (CsHg) for a prenyl-type group. 

Propolis from Europe is the best known type of propolis. In European regions with temperate climate bees obtain resin mainly from the buds of Poplus species and the main bioactive components are flavonoids (Greenaway et al., 1990). In tropical countries, the botanical resources are much more variable in respect to temperate zones, so bees find much more possibilities of collecting resins and hence the chemical composition of tropical propolis are more variable and distinct from European ones (Sawaya et al., 2011). Different compounds have been reported in tropical propolis such as terpenoids and prenylated derivatives of p-coumaric acids in Brazilian propolis (Marcucci, 1995), lignans in Chilean samples (Valcic et al, 1998), and polyisoprenylated benzophenones in Venezuelan, Brazilian, and Cuban propolis (Cuesta-Rubio et al., 1999 Marcucci, 1995). 

D-3-( Acetylt h i o)-2-methyl propanoic aci d 76649-22-4 Prenyl caproate 76649-23-5 Prenyl isobutyrate 76656-36-5 Benzophenone-9 BP-9... 

Using benzophenone as photosensitizer, radical alkenylation of unactivated C (sp )-H bond was developed with 1,2-bis(phenylsulfonyl)ethylene as coupling partner (Scheme 3.28) [80]. A variety of substrates were compatible, including amides, ethers, alcohols, and cycloalkanes. Moreover, the obtained siflfonylalkenes are useful building blocks for the construction of prenyl and pyrrole derivatives. 

Obtained (poor yield) by reaction of prenyl bromide with 2,4,4 -tri-hydroxy-benzophenone,... 

Also obtained (poor yield) by reaction of prenyl bromide with 2,4,6 trihydroxy-benzophenone in the presence of sodium methoxide in refluxing methanol for 3 h [373], (<1%) [374],... 

Also obtained by treahnent of 2,4,6-trihydroxy-benzophenone with prenyl di-n-cyclohexyl-sulfonium tetrafluoroborate salt (1 equiv) in the presence of Hiinig s base (1.1 equiv) in methylene chloride at r.t. for 7 h (10%) [1536]. 

Potassium hydroxide in acetonitrile solution with dicyclohexyl-18-crown-6 gives good yields of aj8-unsaturated nitriles from a variety of aldehydes and ketones, including benzophenone. One consequence of the rate enhancement of the [3,3] sigmatropic rearrangement of certain enolates reported last year by Evans is a new route to prenylated quinones (Scheme 14). A development in the synthesis of olefins by the boron mediated cross-coupling reaction is the use of the boronic... 

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