Search results for "rearrangement"
showing 10 items of 298 documents
Selective favorskii rearrangement in macrocyclic rings
1981
Abstract A mixture of 2,2-dibromo-12-chlorocyclododecanone (IIa) and 2,12-dibromo-2-chlorocyclododecanone (IIb) by Favorskii rearrangement gave selectively methyl 2-chloro-1-cycloundecene-1-carboxylate (IIIa).
Rearrangement products of 3-methanesulfonyl-N-methyl-N-nitroaniline.
2003
Two isomeric products (C 8 H 10 N 2 O 4 S) of the rearrangement of 3-methanesulfonyl-N-methyl-N-nitroaniline have been investigated, viz. 3-methanesulfonyl-N-methyl-2-nitroaniline, which was the main product of the rearrangement, and 5-methanesulfonyl-N-methyl-2-nitroaniline. In both molecules, the aromatic rings are appreciably deformed towards ortho-quinonoidal geometry by electronic and steric interactions. The crystal structure is stabilized, in both cases, by weak C-H...O hydrogen bonds.
Evolutionary stability of topologically associating domains is associated with conserved gene regulation
2018
AbstractBackgroundThe human genome is highly organized in the three-dimensional nucleus. Chromosomes fold locally into topologically associating domains (TADs) defined by increased intra-domain chromatin contacts. TADs contribute to gene regulation by restricting chromatin interactions of regulatory sequences, such as enhancers, with their target genes. Disruption of TADs can result in altered gene expression and is associated to genetic diseases and cancers. However, it is not clear to which extent TAD regions are conserved in evolution and whether disruption of TADs by evolutionary rearrangements can alter gene expression.ResultsHere, we hypothesize that TADs represent essential functiona…
Azoxybenzene rearrangement catalyzed by solid acids
2008
Abstract For the first time, the potential of acidic cation-exchange resin (sulfonated polystyrene) to catalyze the Wallach rearrangement of azoxybenzene into 4-hydroxyazobenzene has been proved. This finding reveals an alternative reaction path possible in a heterogeneous process using solid acids and may help to clear some doubts concerning the rearrangement mechanism postulated so far. The resin-induced reaction was found to proceed exclusively in a non-polar medium. Reasonable yield was obtained particularly in isooctane due to favorable distribution of azoxybenzene throughout the resin's matrix. On the contrary, the HY type zeolite did not activate the rearrangement, most probably beca…
Can the absence of solvation of neutral reagents by ionic liquids be responsible for the high reactivity in base-assisted intramolecular nucleophilic…
2005
[reaction: see text] The kinetics of the rearrangement of the Z-phenylhydrazone of 3-benzoyl-5-phenyl-1,2,4-oxadiazole (1a) into the relevant 4-benzoylamino-2,5-diphenyl-1,2,3-triazole (2a) induced by amines have been studied in two room-temperature ionic liquids (IL-1, [BMIM][BF4] and IL-2, [BMIM][PF6]). The data collected show that the reaction occurs faster in ionic liquids than in other conventional solvents previously studied (both polar or apolar, protic or aprotic). Presumably, this could depend on their peculiar ability to minimize the strong substrate-solvent, amine-solvent and amine-amine interactions occurring in conventional solvents.
Enediolates and dienediolates of carboxylic acids in synthesis. Synthesis of β,γ-epoxyacids from α-chloroketones
1998
Abstract Lithium dienolates of saturated or α,β-unsaturated acids react with α-chloroketones provide a convenient method for preparation of highly sustituted β,γ-epoxyacids. These highly reactive compounds lead in most cases to variable ammounts of the corresponding β-lactones and allylic alcohols.
Synthesis of Spirovetivane Sesquiterpenes from Santonin. Synthesis of (+)-Anhydro-?-rotunol and All Diastereomers of 6,11-Spirovetivadiene.
2005
The synthesis of the spirovetivane sesquiterpenes (+)-anhydro-beta-rotunol and all the diastereomers of 6,11-spirovetivadiene in enantiomerically pure form has been achieved starting from santonin. The key step is the silicon-guided acid-promoted rearrangement of a 1-trimethylsilyl-4,5-epoxyeudesmane prepared from santonin in several steps involving lactone reductive opening, conjugate addition of TMSLi-CuCN, deoxygenation of a carbonyl group, and epoxidation. Rearrangement of the epoxide gave a spiro[4,5]decanediol which was used as a synthetic intermediate. From this compound, (+)-anhydro-beta-rotunol was prepared after elimination of the primary hydroxyl group in the side chain, followed…
Friessche Verschiebung vonortho- undpara-Methoxyphenylacetaten. Die Bildung von Ketoestern
1980
During theFries rearrangement ofo- andp-methoxy phenyl acetates with AlCl3 in nitromethane at 20°C substitution occurs mainly in thep-position of the phenolic residue to yieldp-acylphenols. Larger quantities ofo-acylphenols are obtained only, if thisp-position is already substituted. Witho-methoxy phenyl acetates the substitution of the acid residue to yield ketoesters is observed as a side reaction. Those ketoesters are obtained as main products if TiCl4 is taken as a catalyst.
Settling Down: The Genome of Serratia symbiotica from the Aphid Cinara tujafilina Zooms in on the Process of Accommodation to a Cooperative Intracell…
2014
Particularly interesting cases of mutualistic endosymbioses come from the establishment of co-obligate associations of more than one species of endosymbiotic bacteria. Throughout symbiotic accommodation from a free-living bacterium, passing through a facultative stage and ending as an obligate intracellular one, the symbiont experiences massive genomic losses and phenotypic adjustments. Here, we scrutinized the changes in the coevolution of Serratia symbiotica and Buchnera aphidicola endosymbionts in aphids, paying particular attention to the transformations undergone by S. symbiotica to become an obligate endosymbiont. Although it is already known that S. symbiotica is facultative in Acyrt…
Chromosomal abnormalities in Waldenström's macroglobulinemia
1992
We report the results of cytogenetic studies of direct bone marrow (BM) preparations and of short-term BM and peripheral blood (PB) cultures from 17 patients with Waldenström's macroglobulinemia. We noted clonal chromosome changes in 10 patients. Abnormalities affected chromosomes X, Y, 2, 4, 5, 15, 16, 18, 19, 20, 21, and 22; in particular, chromosomes 2, 4, and 5 were involved in structural changes: a homogeneously staining region [hsr(2)], a der(4)t(4;?)(q32;?), and a 5q+. The other chromosomes were involved in numerical abnormalities, such as pseudodiploidy (a 46,X,-X,+15 clone), loss of chromosome Y, and monosomy of chromosomes 16, 18, 19, 20, 21, and 22. Nonclonal chromosome rearrange…