Stilbene monomers

Grape related products (red wine etc.) usually contain stilbene monomers, dimers and their glycosides [32]. The relative and absolute structures of (-t-)-ampelopsin F (465) [217], (-l-)-isoampelopsin F (468), (-)-ampelopsin F (469) [218-220], isoampelopsin F (467) [221], and those of the structurally related ones 2b-hydroxyampelopsin F (466) [222], gnemonol... 

The stilbene monomers that polymerized to oligostilbenes are depicted in the following ... 

Fig. (1). Numbering of resveratrol (A) and (-)-E-viniferin (B) stilbene monomer is numbered respectively and the different units are distinguished by a, b, c, etc as an example, the numbering of 1 and 3 are shown in Fig. (1).

In some plant species, the production of stilbene monomers and oligomers has been shown to be associated with a variety of stress factors [2,112,120,121,122,123,124]. The stilbene 1 is one of the most commonly encountered of these stress metabolites. While 1 has been shown to exhibit rather modest antimicrobial properties, some of its oligomeric derivatives have demonstrated more potent phytoalexin activity [2,8,125,126]. 

Write structural formulas for maleic anhydride (M ) and stilbene (M2). Neither of these monomers homopolymerize to any significant extent, presumably owing to steric effects. These monomers form a copolymer,... 

It can be determined from the higher effect of the p-substitution compared with the 7-substitution and the high donor ability of the stilbene (ECT = 200 kJ mol-1 x(HOMO) = 0.504 qa = qp = 1.000), that an even electron distribution in the n-system of the donor causing a high electron density in the vicinity of the monomer double bond is important for the strength of the EDA interaction between 71-donor and 7t-acceptor. 

Kool and co-workers recently reported a multicolor set of water-soluble dyes synthesized through the combination of three to five individual fluorophores assembled on a DNA-like backbone [94, 95]. As a continuation of their previous works on various DNA analogs [96-99], they synthesized the oligodeoxyfluoro-side (ODF) with seven fluorescent monomers, such as pyrene, perylene, dimethy-laminostilbene, and three stilbene derivatives, and they assembled these fluorescent DNA monomers into oligofluor chains using a DNA synthesizer (Fig. 26). Using... 

Some monomers with no tendency toward homopolymerization are found to have some (not high) activity in copolymerization. This behavior is found in cationic copolymerizations of tetrahydropyran, 1,3-dioxane, and 1,4-dioxane with 3,3-bis(chloromethyl)oxetane [Dreyfuss and Dreyfuss, 1969]. These monomers are formally similar in their unusual copolymerization behavior to the radical copolymerization behavior of sterically hindered monomers such as maleic anhydride, stilbene, and diethyl fumarate (Sec. 6-3b-3), but not for the same reason. The copolymerizability of these otherwise unreactive monomers is probably a consequence of the unstable nature of their propagating centers. Consider the copolymerization in which M2 is the cyclic monomer with no tendency to homopolymerize. In homopolymerization, the propagation-depropagation equilibrium for M2 is completely toward... 

The dibromo- (and diiodo-) stilbenes ate potentially useful monomers tor the synthesis of poly(p-phenylenevinylenes) via poly-Heck or poly-Suzuki coupling reactions. ... 

A second class of AB benzocyclobutene monomers and polymers which have been reported in the literature are those in which a benzocyclobutene and a stilbene double bond are contained within the same molecule (Fig. 36) [4, 5]. 

The only head-to-head polymer which has been examined for excimer fluorescence is polystyrene 25). Unfortunately, the synthetic route to this polymer leaves a number of stilbene-based structures in the sample, which have a lower-energy singlet state than either PS monomer (285 nm) or excimer (330 nm). Thus, fluorescence from these intrinsic stilbene traps was seen in the spectra of head-to-head PS in pure films and, to a lesser extent, in fluid solution. In the latter, the fluorescence of PS monomer was predominant, and the small amount of stilbene fluorescence was increased when a nonsolvent (methanol or cyclohexane) was added to the 2-methyl-tetrahydrofuran solution. In films of the polymer, stilbene fluorescence was the major spectral band, although some PS excimer fluorescence was also present in the spectrum. No monomer fluorescence at 285 nm was detected from films. Given the impure nature of the head-to-head PS sample, no conclusions on excimer formation in these systems could be drawn. 

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. 

In many binary copolymerizations, there is a pronounced tendency for the two types of monomer unit to alternate along the copolymer chain. In extreme cases, there is almost perfect alteration, notably for pairs of monomers, e.g, maleic anhydride and stilbene, which do not polymerize on their own. Ternary copolymenzations are of practical importance die kinetic treatments developed for binary copolymerizations can be extended to diese systems. 

Exceptionally, when both reactivity ratios are very small, a copolymer is obtained in which both monomers alternate regularly along the chain it is the case, for example, in the copolymerization of maleic anhydride with allyl acetate or with stilbene (29, 142) ... 

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