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Recyclable Cyclohexanediamine Derivatives as Organocatalysts: Organocatalytic Reduction with Trichlorosilane and Aldol Reaction  [PDF]
Yuya Tanimura, Kaori Ishimaru
International Journal of Organic Chemistry (IJOC) , 2013, DOI: 10.4236/ijoc.2013.34034
Abstract:

Reduction of ketimine with trichlorosilane was carried out using bisformamide catalyst 1a derived from cyclohexanediamine to give the corresponding product in 81% yield with 39% ee. Deprotection of the formyl groups of the catalysts 1 gave the corresponding diamines 2 which were utilized in aldol reaction of acetone with 4-nitrobenzaldehyde. The reaction using 2b in brine afforded the aldol adduct in 81% yield with 29% ee.

 

Enantioselective Michael addition of 2-hydroxy-1,4-naphthoquinones to nitroalkenes catalyzed by binaphthyl-derived organocatalysts  [cached]
Saet Byeol Woo,Dae Young Kim
Beilstein Journal of Organic Chemistry , 2012, DOI: 10.3762/bjoc.8.78
Abstract: The highly enantioselective Michael addition of 2-hydroxy-1,4-naphthoquinones to nitroalkenes, promoted by binaphthyl-modified chiral bifunctional organocatalysts is described. This reaction afforded the chiral functionalized naphthoquinones in high yields (81–95%) and excellent enantioselectivities (91–98% ee) under low catalyst loading (1 mol %).
Imidazolinium and amidinium salts as Lewis acid organocatalysts
Oksana Sereda,Nicole Clemens,Tatjana Heckel,René Wilhelm
Beilstein Journal of Organic Chemistry , 2012, DOI: 10.3762/bjoc.8.205
Abstract: The application of imidazolinium and amidinium salts as soft Lewis acid organocatalysts is described. These salts were suitable catalysts for the activation of unsaturated thioesters in a Diels–Alder reaction and in the ring opening of thiiranes and epoxides. The products were isolated in good yields. The mild catalysts did not cause desulfurization of the products containing a thiol or thiocarbonyl group.
Ionic Liquid Immobilized Organocatalysts for Asymmetric Reactions in Aqueous Media  [PDF]
Yupu Qiao,Allan D. Headley
Catalysts , 2013, DOI: 10.3390/catal3030709
Abstract: Ionic liquids are organic salts with melting points typically below ambient or reaction temperature. The unique combination of physical properties of ionic liquids, such as lack of measurable vapor pressure, high thermal and chemical stability, make them ideal to be used as reusable homogenous support for catalysts. In addition, the solubility of ionic liquids in various reaction media can be controlled and easily fine-tuned by modification of the structures of their cations and anions. As a result, ionic liquid immobilized organocatalysts are very effective in aqueous media and can be separated easily from organic solvents, as well as aqueous phases by simply adjusting the polarity of the media. Ionic liquid immobilized organocatalysts are not only very versatile compounds that are effective catalysts for a wide spectrum of reactions, but are also environmentally friendly and recyclable organocatalysts. Herein, we provide a summary of the past decade in the area of asymmetric catalysis in aqueous media for a wide variety of reactions in which ionic liquid and related ammonium salt immobilized organocatalysts are used.
Enantioselective Aldol Reactions and Michael Additions Using Proline Derivatives as Organocatalysts  [PDF]
Mathieu Wagner, Yohan Contie, Clotilde Ferroud, Gilbert Revial
International Journal of Organic Chemistry (IJOC) , 2014, DOI: 10.4236/ijoc.2014.41008
Abstract: Six compounds including five proline derivatives have been prepared and tested as chiral organocatalysts for enantioselective aldol reactions and Michael additions. The enantiomeric excesses, which are highly dependent on the molecular structure of catalysts as well as experimental conditions, have reached over 98%.
Effects of Syzygium aromaticum-Derived Triterpenes on Postprandial Blood Glucose in Streptozotocin-Induced Diabetic Rats Following Carbohydrate Challenge  [PDF]
Andile Khathi, Metse R. Serumula, Rene B. Myburg, Fanie R. Van Heerden, Cephas T. Musabayane
PLOS ONE , 2013, DOI: 10.1371/journal.pone.0081632
Abstract: Purpose Recent reports suggest that the hypoglycaemic effects of the triterpenes involve inhibition of glucose transport in the small intestine. Therefore, the effects of Syzygium spp-derived triterpenes oleanolic acid (OA) and maslinic acid (MA) were evaluated on carbohydrate hydrolyzing enzymes in STZ-induced diabetic rats and consequences on postprandial hyperglycaemia after carbohydrate loading. Methods We determined using Western blot analysis the expressions of α-amylase and α-glucosidase and glucose transporters SGLT1 and GLUT2 in the small intestine intestines isolated from diabetic rats treated with OA/MA for 5 weeks. In vitro assays were used to assess the inhibitory activities of OA and MA against α-amylase, α-glucosidase and sucrase. Results OA and MA ameliorated postprandial hyperglycemia in carbohydrate loaded diabetic rats as indicated by the significantly small glucose area under the curve (AUC) in treated diabetic animals compared with that in untreated diabetic rats. Western blotting showed that OA and MA treatment not only down-regulated the increase of SGLT1 and GLUT2 expressions in the small intestine of STZ-induced diabetic rats, but also inhibited small intestine α-amylase, sucrase and α-glucosidase activity. IC50 values of OA against α-amylase (3.60 ± 0.18 mmol/L), α-glucosidase (12.40 ± 0.11 mmol/L) and sucrase (11.50 ± 0.13 mmol/L) did not significantly differ from those of OA and acarbose. Conclusions The results of suggest that OA and MA may be used as potential supplements for treating postprandial hyperglycemia. Novelty of the Work The present observations indicate that besides improving glucose homeostasis in diabetes, OA and MA suppress postprandial hyperglycaemia mediated in part via inhibition of carbohydrate hydrolysis and reduction of glucose transporters in the gastrointestinal tract. Inhibition of α-glucosidase and α-amylase can significantly decrease the postprandial hyperglycaemia after a mixed carbohydrate diet and therefore can be an important strategy in the management of postprandial blood glucose levels in NIDDM patients.
Synthesis of densely functionalized enantiopure indolizidines by ring-closing metathesis (RCM) of hydroxylamines from carbohydrate-derived nitrones
Bonanni Marco,Marradi Marco,Cardona Francesca,Cicchi Stefano
Beilstein Journal of Organic Chemistry , 2007, DOI: 10.1186/1860-5397-3-44
Abstract: Background Indolizidine alkaloids widely occur in nature and display interesting biological activity. This is the reason for which their total synthesis as well as the synthesis of non-natural analogues still attracts the attention of many research groups. To establish new straightforward accesses to these molecules is therefore highly desirable. Results The ring closing metathesis (RCM) of enantiopure hydroxylamines bearing suitable unsaturated groups cleanly afforded piperidine derivatives in good yields. Further cyclization and deprotection of the hydroxy groups gave novel highly functionalized indolizidines. The synthesis of a pyrroloazepine analogue is also described. Conclusion We have developed a new straightforward methodology for the synthesis of densely functionalized indolizidines and pyrroloazepine analogues in 6 steps and 30–60% overall yields from enantiopure hydroxylamines obtained straightforwardly from carbohydrate-derived nitrones.
Evolutionary patterns of carbohydrate transport and metabolism in Halomonas boliviensis as derived from its genome sequence: influences on polyester production
Daniel Guzmán, Andrea Balderrama-Subieta, Carla Cardona-Ortu?o, Mónica Guevara-Martínez, Nataly Callisaya-Quispe, Jorge Quillaguamán
Aquatic Biosystems , 2012, DOI: 10.1186/2046-9063-8-9
Abstract: The genome sequences and organization in microorganisms should be the result of evolution and adaptation influenced by mutation, gene duplication, horizontal gen transfer (HGT) and recombination. Furthermore, the nearly neutral theory of evolution sustains that genetic modification of DNA could be neutral or selected, albeit most mutations should be at the border between neutrality and selection, i.e. slightly deleterious base substitutions in DNA are followed by a slightly advantageous substitutions.This article reports the genome sequence of H. boliviensis. The chromosome size of H. boliviensis was 4 119 979 bp, and contained 3 863 genes. A total of 160 genes of H. boliviensis were related to carbohydrate transport and metabolism, and were organized as: 70 genes for metabolism of carbohydrates; 47 genes for ABC transport systems and 43 genes for TRAP-type C4-dicarboxylate transport systems. Protein sequences of H. boliviensis related to carbohydrate transport and metabolism were selected from clusters of orthologous proteins (COGs). Similar proteins derived from the genome sequences of other 41 archaea and 59 bacteria were used as reference. We found that most of the 160 genes in H. boliviensis, c.a. 44%, were obtained from other bacteria by horizontal gene transfer, while 13% of the genes were acquired from haloarchaea and thermophilic archaea, only 34% of the genes evolved among Proteobacteria and the remaining genes encoded proteins that did not cluster with any of the proteins obtained from the reference strains. Furthermore, the diversity of the enzymes derived from these genes led to polymorphism in glycolysis and gluconeogenesis. We found further that an optimum ratio of glucose and sucrose in the culture medium of H. boliviensis favored cell growth and PHB production.Results obtained in this article depict that most genetic modifications and enzyme polymorphism in the genome of H. boliviensis were mainly influenced by HGT rather than nearly neutral mutatio
Potential efficacy of preparations derived from Phaseolus vulgaris in the control of appetite, energy intake, and carbohydrate metabolism
Mauro AM Carai, Noemi Fantini, Barbara Loi, et al
Diabetes, Metabolic Syndrome and Obesity: Targets and Therapy , 2009, DOI: http://dx.doi.org/10.2147/DMSO.S4236
Abstract: tential efficacy of preparations derived from Phaseolus vulgaris in the control of appetite, energy intake, and carbohydrate metabolism Commentary (4848) Total Article Views Authors: Mauro AM Carai, Noemi Fantini, Barbara Loi, et al Published Date September 2009 Volume 2009:2 Pages 145 - 153 DOI: http://dx.doi.org/10.2147/DMSO.S4236 Mauro AM Carai1, Noemi Fantini1, Barbara Loi1, Giancarlo Colombo1, Antonella Riva2, Paolo Morazzoni2 1C.N.R. Institute of Neuroscience, Cagliari, Italy; 2Indena SpA, Milan, Italy Abstract: Preclinical data on extracts of and preparations derived from beans of Phaseolus vulgaris are reviewed as potential remedies for use in controlling food consumption, body weight, lipid accumulation, and glycemia. A growing body of evidence suggests that acute and chronic administration of P. vulgaris derivatives reduces food intake (including highly palatable foods), body weight, lipid deposit, and glycemia in rats exposed to multiple experimental procedures. Two possible lectin-mediated mechanisms of action have been proposed: (a) inhibition of α-amylase, resulting in a reduced carbohydrate metabolism and absorption; (b) phytohemoagglutinininduced modulation of the activity of cholecystokinin and glucagon-like peptides, resulting in a reduced appetite. Preliminary clinical data, as well as reports focusing on the use of several traditional medicines, apparently extend these findings to humans. Should these initial clinical data be confirmed by future surveys, P. vulgaris derivatives might constitute novel remedies for the treatment of obesity and metabolic syndrome. Future studies are also expected to identify active structures leading to the development of new pharmaceutical agents.
Carbohydrate Derived Fulvic Acid: An in vitro Investigation of a Novel Membrane Active Antiseptic Agent Against Candida albicans Biofilms  [PDF]
Colin Murray,Owain Millington,Gordon Ramage
Frontiers in Microbiology , 2012, DOI: 10.3389/fmicb.2012.00116
Abstract: Carbohydrate derived fulvic acid (CHD-FA) is a heat stable low molecular weight, water soluble, cationic, colloidal material with proposed therapeutic properties. The aim of this study was to evaluate the antifungal activity of CHD-FA against Candida albicans, and to characterize its mode of action. A panel of C. albicans isolates (n = 50) derived from a range of clinical specimens were grown planktonically and as biofilms, and the minimum inhibitory concentrations determined. Scanning electron microscopy was performed to examine ultrastructural changes and different cell membrane assays were used to determine its mode of action. In addition, the role of C. albicans biofilm resistance mechanisms were investigated to determine their effects on CHD-FA activity. CHD-FA was active against planktonic and sessile C. albicans at concentrations 0.125 and 0.25% respectively, and was shown to be fungicidal, acting through disruption of the cell membrane activity. Resistance mechanisms, including matrix, efflux, and stress, had a limited role upon CHD-FA activity. Overall, based on the promising in vitro spectrum of activity and minimal biofilm resistance of the natural and cheap antiseptic CHD-FA, further studies are required to determine its applicability for clinical use.
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