Browse
Submit Data
Databases
API
Help

Dataset Information

0 Views

0 Connections

0 Citations

0 Reanalyses

0 Downloads

Omics score: 0

Novel amide-functionalized chloramphenicol base bifunctional organocatalysts for enantioselective alcoholysis of meso-cyclic anhydrides.

ABSTRACT: A family of novel chloramphenicol base-amide organocatalysts possessing a NH functionality at C-1 position as monodentate hydrogen bond donor were developed and evaluated for enantioselective organocatalytic alcoholysis of meso-cyclic anhydrides. These structural diversified organocatalysts were found to induce high enantioselectivity in alcoholysis of anhydrides and was successfully applied to the asymmetric synthesis of (S)-GABOB.

SUBMITTER: Xu L

PROVIDER: S-EPMC5815282 | biostudies-other | 2018

REPOSITORIES: biostudies-other

ACCESS DATA

Json Xml

Publications

Novel amide-functionalized chloramphenicol base bifunctional organocatalysts for enantioselective alcoholysis of meso-cyclic anhydrides.

Xu Lingjun L Han Shuwen S Yan Linjie L Wang Haifeng H Peng Haihui H Chen Fener F

Beilstein journal of organic chemistry 20180131

A family of novel chloramphenicol base-amide organocatalysts possessing a NH functionality at C-1 position as monodentate hydrogen bond donor were developed and evaluated for enantioselective organocatalytic alcoholysis of meso-cyclic anhydrides. These structural diversified organocatalysts were found to induce high enantioselectivity in alcoholysis of anhydrides and was successfully applied to the asymmetric synthesis of (S)-GABOB. ...[more]

PMID: 29507636

Similar Datasets

Dual Nickel- and Photoredox-Catalyzed Enantioselective Desymmetrization of Cyclic meso-Anhydrides.

Project description:The enantioselective desymmetrization of cyclic meso-anhydrides with benzyl trifluoroborates under nickel-photoredox catalysis is described. The reaction tolerates a variety of sterically and electronically different trifluoroborates, as well as structurally unique cyclic anhydrides. The trans isomer of the keto-acid products is also observed at varying levels dependent on the trifluoroborate identity and relative catalyst loading. A mechanism involving decarbonylation and Ni-C bond homolysis of a NiII adduct is proposed. This feature allows access to a trans keto-acid as the major product in high enantioselectivity from a cis meso anhydride.

| S-EPMC5510164 | biostudies-literature

Novel bifunctional sulfonamides catalyze an enantioselective conjugate addition.

Project description:A new bifunctional organocatalyst with a novel structural and functional motif has been developed. This bifunctional sulfonamide organocatalyst was used in the conjugate addition of 1,3-dicarbonyl compounds (13) to ?-nitrostyrenes (12). Yields up to 91% and enantiomeric excesses up to 79% were obtained in this reaction. This catalyst activates both 13 via its basic moiety and 12 through hydrogen bonding.

| S-EPMC2659672 | biostudies-literature

meso-3,6-Dioxopiperazine-2,5-diacet-amide.

Project description:The title compound, C(8)H(12)N(4)O(4), was obtained by cyclization of the two l-asparagine mol-ecules and reveals a crystallographic inversion symmetry, and accordingly the two stereogenic centres are of opposite chirality. Thus, an asymmetric unit comprises a half of a mol-ecule. The mol-ecules are assembled into a three-dimensional hydrogen-bonding network by N-H?O hydrogen bonds.

| S-EPMC3247435 | biostudies-literature

Ethyne Functionalized Meso-Phenothiazinyl-Phenyl-Porphyrins: Synthesis and Optical Properties of Free Base Versus Protonated Species.

Project description:Synthesis, structural characterization and photophysical properties for a series of new trans-A2B2- and A3B-type ethynyl functionalized meso-phenothiazinyl-phenyl porphyrin derivatives are described. The new compounds displayed the characteristic porphyrin absorption spectra slightly modified by weak auxochromic effects of the substituents and fluorescence emission in the range of 651-659 nm with 11-25% quantum yields. The changes recorded in the UV-vis absorption spectra in the presence of trifluoroacetic acid (TFA) are consistent with the protonation of the two internal nitrogen atoms of the free-base porphyrin (19 nm bathochromic shift of the strong Soret band and one long wave absorption maxima situated in the range of 665-695 nm). Protonation of the phenothiazine substituents required increased amounts of TFA and produced a distinct hypsochromic shift of the long wave absorption maxima. The density functional theory (DFT) calculations of a porphyrin dication pointed out a saddle-distorted porphyrin ring as the ground-state geometry.

| S-EPMC7583012 | biostudies-literature

Highly Efficient Bifunctional Amide Functionalized Zn and Cd Metal Organic Frameworks for One-Pot Cascade Deacetalization-Knoevenagel Reactions.

Project description:A pyridine-based amide functionalized tetracarboxylic acid, 5,5'-(pyridine-2, 6-dicarbonyl)bis(azanediyl)}diisophthalic acid (H4L), was synthesized and its coordination chemistry toward zinc(II) and cadmium(II) ions was studied. The reactions of H4L with Zn(NO3)2.6H2O and Cd(NO3)2.4H2O led to its full or partial deprotonation, respectively, and the formation of the 2D coordination polymers [Zn2(L)(H2O)4]n.4n(H2O) (1) and [Cd3(HL)2(DMF)4]n.4n(DMF) (2) (DMF = N,N'-dimethylformamide), respectively. They were characterized by elemental analysis, FT-IR, photoluminescence, thermogravimetry, and single-crystal and powder X-ray diffraction. In 1, the L4- ligand is planar with every carboxylate anion binding a Zn(II) cation and giving rise to a 2D grid with the metals with tetrahedral environments. In 2, the combination of bridging HL3- and dimethylformamide to form trinuclear Cd(II) clusters engenders secondary building block units and generates a layer-type 2D network with the metals with octahedral and pentagonal bipyramid coordination geometries. The topological analyses of 1 and 2 reveal 2,4-connected and 3,6-connected binodal nets, respectively. On account of the presence of Lewis acid (Zn or Cd centers) as well as basic (uncoordinated pyridine and amide groups) sites, 1 and (to a much lower extent) 2 effectively catalyze the one-pot cascade deacetalization-Knoevenagel condensation reactions under quite mild conditions. They act as heterogeneous catalysts, being easy to recover and recycle without losing activity.

| S-EPMC6824099 | biostudies-literature

Base-free enantioselective SN2 alkylation of 2-oxindoles via bifunctional phase-transfer catalysis.

Project description:N-Protected oxindole derivatives of unprecedented malleability bearing ester moieties at C-3 have been shown to participate in enantioselective phase-transfer-catalysed alkylations promoted by ad-hoc designed quaternary ammonium salts derived from quinine bearing hydrogen-bond donating substituents. For the first time in such phase-transfer-catalysed enolate alkylations, the reactions were carried out under base-free conditions. It was found that urea-based catalysts outperformed squaramide derivatives, and that the installation of a chlorine atom adjacent to the catalyst's quinoline moiety aided in avoiding selectivity-reducing complications related to the production of HBr in these processes. The influence of steric and electronic factors from both the perspective of the nucleophile and electrophile were investigated and levels of enantiocontrol up to 90% ee obtained. The synthetic utility of the methodology was demonstrated via the concise enantioselective synthesis of a potent CRTH2 receptor antagonist.

| S-EPMC8450950 | biostudies-literature

Enantioselective cross-coupling of meso-epoxides with aryl halides.

Project description:The first enantioselective cross-electrophile coupling of aryl bromides with meso-epoxides to form trans-?-arylcycloalkanols is presented. The reaction is catalyzed by a combination of (bpy)NiCl2 and a chiral titanocene under reducing conditions. Yields range from 57 to 99% with 78-95% enantiomeric excess. The 30 examples include a variety of functional groups (ether, ester, ketone, nitrile, ketal, trifluoromethyl, sulfonamide, sulfonate ester), both aryl and vinyl halides, and five- to seven-membered rings. The intermediacy of a carbon radical is strongly suggested by the conversion of cyclooctene monoxide to an aryl [3.3.0]bicyclooctanol.

| S-EPMC4415026 | biostudies-literature

Enantioselective synthesis of (-)-chloramphenicol via silver-catalysed asymmetric isocyanoacetate aldol reaction.

Project description:The highly enantio- and diastereoselective aldol reaction of isocyanoacetates catalysed by Ag2O and cinchona-derived amino phosphines applied to the synthesis of (-)- and (+)-chloramphenicol is described. The concise synthesis showcases the utility of this catalytic asymmetric methodology for the preparation of bioactive compounds possessing α-amino-β-hydroxy motifs.

| S-EPMC4756631 | biostudies-literature

Inactivation of chloramphenicol and florfenicol by a novel chloramphenicol hydrolase.

Project description:Chloramphenicol and florfenicol are broad-spectrum antibiotics. Although the bacterial resistance mechanisms to these antibiotics have been well documented, hydrolysis of these antibiotics has not been reported in detail. This study reports the hydrolysis of these two antibiotics by a specific hydrolase that is encoded by a gene identified from a soil metagenome. Hydrolysis of chloramphenicol has been recognized in cell extracts of Escherichia coli expressing a chloramphenicol acetate esterase gene, estDL136. A hydrolysate of chloramphenicol was identified as p-nitrophenylserinol by liquid chromatography-mass spectroscopy and proton nuclear magnetic resonance spectroscopy. The hydrolysis of these antibiotics suggested a promiscuous amidase activity of EstDL136. When estDL136 was expressed in E. coli, EstDL136 conferred resistance to both chloramphenicol and florfenicol on E. coli, due to their inactivation. In addition, E. coli carrying estDL136 deactivated florfenicol faster than it deactivated chloramphenicol, suggesting that EstDL136 hydrolyzes florfenicol more efficiently than it hydrolyzes chloramphenicol. The nucleotide sequences flanking estDL136 encode proteins such as amidohydrolase, dehydrogenase/reductase, major facilitator transporter, esterase, and oxidase. The most closely related genes are found in the bacterial family Sphingomonadaceae, which contains many bioremediation-related strains. Whether the gene cluster with estDL136 in E. coli is involved in further chloramphenicol degradation was not clear in this study. While acetyltransferases for chloramphenicol resistance and drug exporters for chloramphenicol or florfenicol resistance are often detected in numerous microbes, this is the first report of enzymatic hydrolysis of florfenicol resulting in inactivation of the antibiotic.

| S-EPMC3416615 | biostudies-literature

DFT-Based Stereochemical Rationales for the Bifunctional Bronsted Acid/Base-Catalyzed Diastereodivergent and Enantioselective aza-Henry Reactions of α-Nitro Esters.

Project description:A pair of chiral bis(amidine) [BAM] proton complexes provide reagent (catalyst)-controlled, highly diastereo- and enantioselective direct aza-Henry reactions leading to α-alkyl-substituted α,β-diamino esters. A C2-symmetric ligand provides high anti-selectivity, while a nonsymmetric congener exhibits syn-selectivity in this example of diastereodivergent, enantioselective catalysis. A detailed computational analysis is reported for the first time, one that supports distinct models for selectivity resulting from the more hindered binding cavity of the C1-symmetric ligand. Binding in this congested pocket accommodates four hydrogen bond contacts among ligands and substrates, ultimately favoring a pre-syn arrangement highlighted by pyridinium-azomethine activation and quinolinium-nitronate activation. The complementary transition states reveal a wide range of alternatives. Comparing the C1- and C2-symmetric catalysts highlights distinct electrophile binding orientations despite their common hydrogen bond donor-acceptor features. Among the factors driving unusual high syn-diastereoselection are favorable dispersion forces that leverage the anthracenyl substituent of the C1-symmetric ligand.

| S-EPMC8899924 | biostudies-literature