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Aryl Migration (aryl + migration)
Selected AbstractsPd-Catalyzed Alkyl to Aryl Migration and Cyclization: An Efficient Synthesis of Fused Polycycles via Multiple C,H Activation.CHEMINFORM, Issue 43 2004Qinhua Huang No abstract is available for this article. [source] Thermal transformation of arylamidoximes in the presence of phosphorus ylides.JOURNAL OF HETEROCYCLIC CHEMISTRY, Issue 4 20044-oxadiazoles, Unexpected formation of 3-aryl-5-arylamino- The unexpected formation of 3-aryl-5-arylamino-1,2,4-oxadiazoles took place, when arylamidoximes reacted thermally with ethoxycarbonylmethylene(triphenyl)phosphorane. Furoxans, nitriles, ureas were also isolated suggesting aryl cyanide oxides as intermediates. 3-Aryl-5-arylamino-1,2,4-oxadiazoles were formed via an aryl migration from the carbon atom to the nitrogen atom of the amidoxime, and the structure was further proved from the X-ray crystal structure of the N -(4-bromobenzoyl) derivative. [source] Evidence for an aryl migration during the electron impact induced fragmentation of substituted aryloxymethylquinoxalinesRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 3 2002I. Starke The electron impact (EI) mass spectra of 34 differently substituted 2-phenoxymethyl-, 2-naphthyloxymethyl-, 2-pyridinyloxymethyl- and 2-chinolinyloxymethylquinoxalines were recorded. The fragmentation patterns were examined by metastable ion analysis and exact mass measurements, employing finally also selective deuterium labelling. The inclusion of the substituted aryl ring moiety appears to be important for the fragmentation of the aryloxymethylquinoxalines. A molecular ion rearrangement is proposed for the observed loss of OH· and CHO· radicals. The influence of the different substituents on the aryl ring moiety on the rearrangement in the gas phase and on the resulting fragmentation was investigated. Copyright © 2001 John Wiley & Sons, Ltd. [source] Key amino acid residues required for aryl migration catalysed by the cytochrome P450 2-hydroxyisoflavanone synthaseTHE PLANT JOURNAL, Issue 5 2002Yuji Sawada Summary Isoflavonoids are distributed predominantly in leguminous plants, and play pivotal roles in the interaction of host plants with biological environments. Isoflavones in the diet also have beneficial effects on human health as phytoestrogens. The isoflavonoid skeleton is constructed by the CYP93C subfamily of cytochrome P450s in plant cells. The reaction consists of hydroxylation of the flavanone molecule at C-2 and an intramolecular 1,2-aryl migration from C-2 to C-3 to yield 2-hydroxyisoflavanone. In this study, with the aid of alignment of amino acid sequences of CYP93 family P450s and a computer-generated putative stereo structure of the protein, candidates for key amino acid residues in CYP93C2 responsible for the unique aryl migration in 2-hydroxyisoflavanone synthase reaction were identified. Microsomes of recombinant yeast cells expressing mutant proteins of CYP93C2 were prepared, and their catalytic activities tested. The reaction with the mutant in which Ser 310 in the centre of the I-helix was converted to Thr yielded increased formation of 3-hydroxyflavanone, a by-product of the 2-hydroxyisoflavanone synthase reaction, in addition to the major isoflavonoid product. More dramatically, the mutant in which Lys 375 in the end of ,-sheet 1,4 was replaced with Thr produced only 3-hydroxyflavanone and did not yield the isoflavonoid any longer. The roles of these amino acid residues in the catalysis and evolution of isoflavonoid biosynthesis are discussed. [source] | ||||||||||