|
| ||
|
|
||
Biphenyl Derivative (biphenyl + derivative)
Selected AbstractsThe Superbase-Mediated Pairwise Substitution of the 2,2,- and 6,6,-Positions in a Biphenyl DerivativeEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 5 2004Manfred Schlosser Abstract The superbasic mixture of butyllithium and potassium tert -butoxide is powerful enough to enable the double proton abstraction from one ortho and one ortho, position of 4,4,-di- tert -butylbiphenyl. In this way, a series of functionalized derivatives becomes readily accessible, among them 4,4,-di- tert -butylbiphenyldiyl-2,2,-dicarboxylic acid (2a) and 4,4,-di- tert -butylbiphenyl-2,2,-diol (2d). The latter compound can be subjected again to a superbase-promoted double metalation, thus giving rise to 2,2,,6,6,-tetrasubstituted biphenyl derivatives. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004) [source] Down-Regulation of Melanin Synthesis by a Biphenyl Derivative and Its MechanismPIGMENT CELL & MELANOMA RESEARCH, Issue 5 2003Kyoko Nakamura Down-regulation of melanin synthesis is required for recovery of pigmentary disorders and it is known that direct inhibitors of tyrosinase, the key enzyme in melanin synthesis, such as hydroquinone with a phenol structure, suppress melanin synthesis. We screened several phenolic derivatives using B16 melanoma cells and found that a biphenyl derivative, 2,2,-dihydroxy-5,5,-dipropyl-biphenyl (DDB), down-regulated melanin synthesis effectively. Although DDB has a phenol structure, it did not inhibit tyrosinase in vitro, thus we examined its mechanism in detail. Western blotting revealed that the amount of tyrosinase was decreased by DDB, and pulse-chase labeling and immunoprecipitation analysis showed a decrease of mature tyrosinase and acceleration of tyrosinase degradation in its presence. These results suggest that DDB down-regulates melanin synthesis by inhibiting the maturation of tyrosinase, leading to acceleration of tyrosinase degradation. [source] ChemInform Abstract: Synthesis of Highly Oxygenated Biphenyl Derivative (VI) in an Optically Active Form Through Palladium-Mediated Intramolecular Biaryl Coupling Reaction.CHEMINFORM, Issue 9 2009Hitoshi Abe Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source] Down-Regulation of Melanin Synthesis by a Biphenyl Derivative and Its MechanismPIGMENT CELL & MELANOMA RESEARCH, Issue 5 2003Kyoko Nakamura Down-regulation of melanin synthesis is required for recovery of pigmentary disorders and it is known that direct inhibitors of tyrosinase, the key enzyme in melanin synthesis, such as hydroquinone with a phenol structure, suppress melanin synthesis. We screened several phenolic derivatives using B16 melanoma cells and found that a biphenyl derivative, 2,2,-dihydroxy-5,5,-dipropyl-biphenyl (DDB), down-regulated melanin synthesis effectively. Although DDB has a phenol structure, it did not inhibit tyrosinase in vitro, thus we examined its mechanism in detail. Western blotting revealed that the amount of tyrosinase was decreased by DDB, and pulse-chase labeling and immunoprecipitation analysis showed a decrease of mature tyrosinase and acceleration of tyrosinase degradation in its presence. These results suggest that DDB down-regulates melanin synthesis by inhibiting the maturation of tyrosinase, leading to acceleration of tyrosinase degradation. [source] Functionalized 3,3,,5,5,-Tetraaryl-1,1,-Biphenyls: Novel Platforms for Molecular ReceptorsHELVETICA CHIMICA ACTA, Issue 3 2003Roger Welti This paper describes the development of novel aromatic platforms for supramolecular construction. By the Suzuki cross-coupling protocol, a variety of functionalized m- terphenyl derivatives were prepared (Schemes,1,4). Macrolactamization of bis(ammonium salt) (S,S)- 6 with bis(acyl halide) 7 afforded the macrocyclic receptor (S,S)- 2 (Scheme,1), which was shown by 1H-NMR titration studies to form ,nesting' complexes of moderate stability (Ka between 130 and 290,M,1, 300,K) with octyl glucosides 13,15 (Fig.,2) in the noncompetitive solvent CDCl3. Suzuki cross-coupling starting from 3,3,,5,5,-tetrabromo-1,1,-biphenyl provided access to a novel series of extended aromatic platforms (Scheme,5) for cleft-type (Fig.,1) and macrotricyclic receptors such as (S,S,S,S)- 1. Although mass-spectral evidence for the formation of (S,S,S,S)- 1 by macrolactamization between the two functionalized 3,3,,5,5,-tetraaryl-1,1,-biphenyl derivatives (S,S)- 33 and 36 was obtained, the 1H- and 13C-NMR spectra of purified material remained rather inconclusive with respect to both purity and constitution. The versatile access to the novel, differentially functionalized 3,3,,5,5,-tetrabromo-1,1,-biphenyl platforms should ensure their wide use in future supramolecular construction. [source] Bis(imino)pyridine palladium(II) complexes as efficient catalysts for the Suzuki,Miyaura reaction in waterAPPLIED ORGANOMETALLIC CHEMISTRY, Issue 2 2010Ping Liu Abstract Bis(imino)pyridine palladium(II) complexes 3 and 4 of type [PdCl(L)PF6] are found to be efficient catalysts for Suzuki,Miyaura reactions of aryl halides and arylboronic acids. The reactions proceed smoothly to generate the corresponding biaryl compounds in moderate to excellent yields. The synthesis of various fluorinated biphenyl derivatives was successfully achieved by the complex 4 catalyzed the Suzuki,Miyaura reaction in the presence of surfactants bearing a long alkyl chain. Copyright © 2009 John Wiley & Sons, Ltd. [source] Polyphenols from Polygala spp. and Their Antioxidant ActivityCHEMISTRY & BIODIVERSITY, Issue 3 2004Rinaldo Cervellati Members of Polygalaceae are known to contain a variety of different polyphenolic compounds such as xanthones, flavonoids, and biphenyl derivatives. Here, we report the isolation and structural characterization of two new phenol derivatives, named alpestrin (=3,3,,5,-trimethoxy[1,1,-biphenyl]-4-ol; 10) and alpestriose,A (=6- O -benzoyl-1- O -{6- O -acetyl-3- O -[(4-hydroxy-3,5-dimethoxyphenyl)prop-2-enoyl]- , - D -fructofuranosyl}- , - D -glucopyranoside; 11), and of four known compounds (12,15) from the MeOH extract of Polygala alpestris. The relative in vitro antioxidant activities of these compounds, in comparison with other phenolic substances from Polygala vulgaris, were evaluated by means of the BriggsRauscher (BR) oscillating reaction, a method based on the inhibitory effects of antioxidant free-radical scavengers. The experimental antioxidant-activity values (relative to resorcinol as a standard) were compared with those calculated on the basis of the bond-dissociation enthalpies. The structure/activity relationships for the compounds examined are also discussed. [source] | ||||||||||