Of stilbene derivatives

Most of the olefins shown so far, for which reversibility of the bromonium ion formation had been demonstrated, are particular olefins, in which either steric bulk impedes the product forming step, or ring strain in the dibromide product retards this step. In order to check the general occurrence of the reversibility during the bromination reaction, a further approach, based on the cis-trans isomerization of stilbene derivatives during the bromination of the cis isomers, was devised. 

The pharmacological potential of this tree is unexplored. Note that Cryptocarya species are very interesting, as they have the tendency to elaborate a series of stilbenes derivatives known as a-pyrones (112,113). The neuropharmacological potential of such... 

For example, stilbene oxygenases, which cleave the interphenyl a,P-double bond of stilbene derivatives, are known to be members of the CCO family of enzymes that act on substrates other than... 

Marasco, E. and C. Schmidt-Dannert (2008). Identification of bacterial carotenoid cleavage dioxygenase homologs that cleave the interphenyl u,(J double bond of stilbene derivatives via a monooxygenase reaction. Chembiochem. 9(9) 1450-1461. 

Synthesis of the phenyl derivative (138) was also described by Simoni et al. [60] and employs the same synthetic strategy as for the pyridine derivative (137) described in Scheme 34. No biological activity was reported for this compound, but it was included in order to provide a broader coverage of stilbene derivatives. 

When the dehydration of 39 was carried out (H3PO4 or DMSO under reflux) instead of its dehydroxylation, a different class of stilbene derivatives, such as pinosilvine 44, resveratrol 45 or piceatannol 46, were easily obtained . From these compounds, resver-atrol has shown very potent anticancer properties in vivo, this activity being proven in rats . 

Kimura, Y. Okuda, H. Arichi, S. Effects of stilbene derivatives on archodouaic metabolism in leukocytes. Biochim. Biophys. Acta 1985, 837, 209-212. 

The conclusion that the ac electrolysis of Re rans-SP CCCOjCl proceeds via excited states is also supported by the direction of isomerization. In thermal reactions of stilbene derivatives and radicals cis to trans conversions are generally observed (61). Contrary to this behavior the photolysis and ac electrolysis lead to energetically uphill trans to cis isomerization. 

Yasuda, M., Isami, T., Kubo, J., Mizutani, M., Yamashita, T., and Shima, K. (1992) Regiochemistry on photoamination of stilbene derivatives with ammonia via electron transfer. Journal of Organic Chemistry, 57, 1351—1354. 

Photoamination of a variety of aromatic compounds with ammonia and alkyl-amines under photosensitized electron transfer mediated reaction conditions has been extensively investigated by Yasuda and coworkers (Scheme 70) [320-324]. The photoamination reactions of stilbene derivatives with ammonia have been utilized for the synthesis of a variety of isoquinoline derivatives [324]. The photoamination is initiated by photochemical electron transfer from the arenes to the electron acceptor followed by nucleophilic attack of ammonia or primary amines on the aromatic radical cations (Scheme 70). 

Effects of stilbene derivatives on ADP plus NADPH-induced lipid peroxidation in rat liver microsomes. 

Silver ions cause perturbation of the (E)-(Z) photoisomerization pathway for both stilbene and azobenzene . The efficiency of silver ions in this respect is compared with the effect of Nal which can only induce a heavy atom effect. Ag+ clearly forms complexes with both compounds. Observation of cis-trans conversion in olefin radical cations shows that electron transfer can bring about isomerization of stilbene derivatives. The efficiency of such processes obviously depends on the presence and nature of any substituents. Another study deals with photochemical generation, isomerization, and effects of oxygenation on stilbene radicals. The intermediates examined were generated by electron transfer reactions. Related behaviour probably occurs through the effect of exciplex formation on photoisomerization of styrene derivatives of 5,6-benz-2,2 -diquinoyE. ... 

The photophysical and photochemical properties of a series of stilbene derivatives such as (7) and (8) have been investigated. The fluorescence spectra of l,T-bi(benzocyclobutylidene), a rigid stilbene, has been investigated. "... 

Conversion of stilbene derivatives to phenanthrenes with VOF3 in trifluoroacetic acid (TFA). 

Addition reactions. cfr-Addition of ArMgBr to alkynes leads to styryhnagnesium bromides. Regioselective generation of stilbene derivatives from arylalkynes is observed. ... 

A large number of stilbenes derived from 3-(p-tolyl)indoxazene have been prepared and their fluorescence spectra measured.74... 

Table 16. The Inhibitory Effects of Stilbene Derivatives on PG Biosynthesis...

The quantum yield of the cis-trans isomerization of stilbene derivatives, in particular surfactant stilbenes, depends on the fluidity of the environment. 

A Pd-modified zeolite NaY was utiUzed as a heterogeneous catalyst for Heck reactions of 4-choroacetophenone [161,162]. Entrapped [Pd(NH3)4] gave yields of about 60% of stilbene derivatives with palladium amounts of 0.1mol% (170 °C,... 

The geometries, electronic structures and electronic spectra of stilbene derivatives and chromophores based on dithienothiophenes are systematically studied by AMI and INDO/CI method. On the basis of correct UV-Vis spectra, the position and strength of the two-photon absorption can be predicted (2001MI1). 

Isomerization, Oxidation, and Dimerization of Radical Cations of Stilbene Derivatives... 

Scheme 13.29 Photocyclization of stilbene derivatives towards heteroatom-containing PAHs 104-106.

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