417 research outputs found
2-Keto-3-deoxy-6-phosphogalactonate Aldolase as a Catalyst for Stereocontrolled Carbon−Carbon Bond Formation
No full text2-Keto-3-deoxy-6-phosphogalactonate
Aldolase as a Catalyst for Stereocontrolled
Carbon−Carbon Bond Formatio
New Complexity-Building Reactions of α-Keto Esters
No full textI. Introduction: Importance of Asymmetric Catalysis and the Reactivity Patterns of α-Keto Esters II. Synthesis of Complex Tertiary Glycolates by Enantioconvergent Arylation of Stereochemically Labile α-Keto Esters Enantioconvergent arylation reactions of boronic acids and racemic β-stereogenic α-keto esters have been developed. The reactions are catalyzed by a chiral (diene)Rh(I) complex and provide a wide array of β-stereogenic tertiary aryl glycolate derivatives with high levels of diastereo- and enantioselectivity. Racemization studies employing a series of sterically differentiated tertiary amines suggest that the steric nature of the amine base additive exerts a significant influence on the rate of substrate racemization. III. Palladium-Catalyzed β-Arylation of α-Keto Esters A catalyst system derived from commercially available Pd2(dba)3 and PtBu3 has been applied to the coupling of α-keto ester enolates and aryl bromides. The reaction provides access to an array of β-stereogenic α-keto ester derivatives. When the air stable ligand precursor PtBu3·HBF4 is employed, the reaction can be carried out without use of a glovebox. The derived products are of broad interest given the prevalence of the α-keto acid substructure in biologically important molecules. IV. Catalytic Enantioselective [3+2] Cycloaddition of α-Keto Ester Enolates and Nitrile Oxides An enantioselective [3+2] cycloaddition reaction between nitrile oxides and transiently generated enolates of α-keto esters has been developed. The catalyst system was found to be compatible with in situ nitrile oxide generation conditions. A versatile array of nitrile oxides and α-keto esters could participate in the cycloaddition, providing novel 5-hydroxy-2-isoxazolines in high chemical yield with high levels of diastereo- and enantioselectivity. Notably, the optimal reaction conditions circumvented concurrent reaction via O-imidoylation and hetero-[3+2] pathways.Doctor of Philosoph
The Decrease of Specific Angular Momentum and the Hot Toroid Formation: The Massive Clump G10.6–0.4
No full textScientific Analysis and Comparison Between Bigu and Keto Diet
No full textChinese Taoists have a long traditional practice of "Bigu", which has a similar process and results as the ketogenic diet, or Keto, that has recently become popular. These diet regiments make people lose weight, reduce their appetite, increase energy, and think clearly. Keto was used in the twentieth century to treat epilepsy and later became a popular form of health practice - a rich-fat, moderate protein, and minimal carbohydrates diet that forces the human body to burn fat rather than carbohydrates as the primary calorie source. In 2016, Prof. Koizumi of Japan provided the scientific basis of the ketogenic diet and won the Nobel Prize. “Bigu”, which means “Avoid Grain” in Chinese, has been a way of health preservation in China for thousands of years. There are surprisingly few research projects comparing these two popular diet practices. This paper surveys and analyzes the recent researches to compare the differences between Bigu and Keto, proposes new bigu standards, and recommends future research directions
Data_Sheet_1_Enzymatic Synthesis of 2-Keto-3-Deoxy-6-Phosphogluconate by the 6-Phosphogluconate-Dehydratase From Caulobacter crescentus.pdf
No full textThe availability of metabolic intermediates is a prerequisite in many fields ranging from basic research, to biotechnological and biomedical applications as well as diagnostics. 2-keto-3-deoxy-6-phosphogluconate (KDPG) is the key intermediate of the Entner-Doudoroff (ED) pathway for sugar degradation and of sugar acid and sugar polymer breakdown in many organisms including human and plant pathogens. However, so far KDPG is hardly available due to missing efficient synthesis routes. We here report the efficient biocatalytic KDPG production through enzymatic dehydration of 6-phosphogluconate (6PG) up to gram scale using the 6PG dehydratase/Entner-Doudoroff dehydratase (EDD) from Caulobacter crescentus (CcEDD). The enzyme was recombinantly produced in Escherichia coli, purified to apparent homogeneity in a simple one-step procedure using nickel ion affinity chromatography, and characterized with respect to molecular and kinetic properties. The homodimeric CcEDD catalyzed the irreversible 6PG dehydration to KDPG with a Vmax of 61.6 U mg–1 and a KM of 0.3 mM for 6PG. Most importantly, the CcEDD showed sufficient long-term stability and activity to provide the enzyme in amounts and purity required for the efficient downstream synthesis of KDPG. CcEDD completely converted 1 g 6PG and a straight forward purification method yielded 0.81 g of stereochemically pure KDPG corresponding to a final yield of 90% as shown by HPLC-MS and NMR analyses.</p
Synthesis of a series of 16, 16-dimethyl-prostacyclin and 6-keto prostaglandin analogs, 1978
No full textA synthesis is described for a number of 16,16-dimethyl analogs of the prostacyclin and related 6-keto prostaglandin types. Included are l6, l6-dimethyl-PGI2 sodium salt (XLIV), 6?-l6, l6-dimethyl-PGI1(XLV), 6?-l6, l6-dimethyl-PGI1 (XLVII), 6-keto-l6, l6-dimethyl-PGF1-? (XLIX), and 6-keto-l6, l6-dimethyl PGE1 (LV). Done, but not included, is the activity for these analogs in the blood platelet aggregation inhibition assay. This activity was consistently less than for the corresponding 16, 16-dihydro compounds
Thiourea catalysed reduction of alpha-keto substituted acrylate compounds using Hantzsch ester as a reducing agent in water
No full textThe first method for the reduction of alpha-keto substituted acrylate compounds by Hantzsch ester in water under the catalysis of thiourea has been developed. The products were isolated in moderate to high yields (38-95%). These products are important intermediates in the synthesis of a series of natural products and other biologically active molecules
Recovery of Arenes Containing Keto or Ester Groups by the Electrochemical Reduction of Their Respective Cyclopentadienyliron Complexes
No full textElectrochemical reduction of the cyclopentadienyliron hexafluorophosphates of benzophenone, o-chlorophenyldibenzoylmethane and diethyl ethylphenylmalonate led to the liberation of arenes without reduction of keto or ester groups in over 85% yields
Asymmetric Hydrogenation of α-Alkyl-Substituted β-Keto Esters and Amides through Dynamic Kinetic Resolution
No full textAsymmetric hydrogenation of alpha-alkyl-substituted beta-keto esters and amides with the DIPSkewphos/3-AMIQ-Ru(II) catalyst system through dynamic kinetic resolution was examined. A series of beta-keto esters and amides with a simple or functionalized alpha-alkyl group were applicable to this reaction, affording the alpha-substituted beta-hydroxy esters and amides in >= 99% ee (anti/syn >= 99:1) in many cases. The 5 g scale reaction was readily achieved. The mode of enantio- and diastereoselection in the transition state model was proposed
- …
