Downloads & Free Reading Options - Results

This work develops a general synthesis of the Prosopis africana alkaloids, using a chiral auxiliary-mediated process. Enantiopure N-acyldihydropyridones were produced and used as intermediates, targeting (+)-desoxoprosopinine as a synthetic model for those alkaloids. The orientation of all three stereocenters was highly controlled, with the synthesis of intermediate 75, just short of the target, in 7 steps with a 13.8% overall yield.

This work develops a general synthesis of the Prosopis africana alkaloids, using a chiral auxiliary-mediated process. Enantiopure N-acyldihydropyridones were produced and used as intermediates, targeting (+)-desoxoprosopinine as a synthetic model for those alkaloids. The orientation of all three stereocenters was highly controlled, with the synthesis of intermediate 75, just short of the target, in 7 steps with a 13.8% overall yield.

During the funding period, we have made significant progress both in the developing new methods for asymmetric synthesis and discovering new liquid crystal materials. Over a dozen of papers have been published or in press in several journals (J. Am. Chem. Soc., J. Org. Chem. and Tetrahedral Letter) and three have been submitted for publication. We have developed a chiral toolbox with a large set of chiral ligands for asymmetric catalysis. These includes helical ligands, chiral monophosphines, chiral tridentate ligands and novel chiral bidentate phosphines with rigid backbones. Excellent activities and enantioselectivities (up to 99 % ee) have been observed in many asymmetric reactions such as hydride transfer reaction, hydrogenation, alkylation of aldehydes, cycloaddition and allylic alkylation. Seven patents have been filed and several companies (Catalytica and Pfizer) have licensed this technology for the production of chiral molecules in industrial scales. Using these methods and other organometallic methodologies, we have made a number of chiral liquid crystals and related materials. We are developing high polarization materials as candidates of novel ferroelectric liquid crystals. The viscosity of a diphenyl-diacetylene liquid crystals is far lower than the corresponding quadra-phenyl liquid crystals. We have synthesized chiral liquid crystals using this conjugated backbone (diphenyl diacetylene). We also plans to change the arrangement of the phenyl-acetylene modules and these changes could alter the physical properties of liquid crystals in useful ways (e.g., absorption efficiency of Laser lines). This research is carried out in collaboration with Professor I. C. Khoo in Department of Electrical Engineering at Penn State University. The research collaboration with Professor Khoo has resulted in excellent laser optical limiting materials.

xii,380p. : 24 cm

Click here to view the University of Florida catalog record

Click here to view the University of Florida catalog record

This article is from Beilstein Journal of Organic Chemistry , volume 10 . Abstract Virgin females of the parasitoid wasp Trichogramma turkestanica produce minute amounts of a sex pheromone, the identity of which has not been fully established. The enantioselective synthesis of a putative component of this pheromone, (6S,8S,10S)-4,6,8,10-tetramethyltrideca-2E,4E-dien-1-ol (2), is reported as a contribution to this identification. Catalytic asymmetric conjugate addition of methylmagnesium bromide and stereoselective Horner–Wadsworth–Emmons olefinations are used as the key steps, and 2 was obtained in 16 steps with an overall yield of 4.4%.

This article is from Beilstein Journal of Organic Chemistry , volume 9 . Abstract A continuous-flow asymmetric organocatalytic photocyclization–transfer hydrogenation cascade reaction has been developed. The new protocol allows the synthesis of tetrahydroquinolines from readily available 2-aminochalcones using a combination of photochemistry and asymmetric Brønsted acid catalysis. The photocylization and subsequent reduction was performed with catalytic amount of chiral BINOL derived phosphoric acid diester and Hantzsch dihydropyridine as hydrogen source providing the desired products in good yields and with excellent enantioselectivities.

This article is from Beilstein Journal of Organic Chemistry , volume 9 . Abstract A continuous-flow asymmetric organocatalytic photocyclization–transfer hydrogenation cascade reaction has been developed. The new protocol allows the synthesis of tetrahydroquinolines from readily available 2-aminochalcones using a combination of photochemistry and asymmetric Brønsted acid catalysis. The photocylization and subsequent reduction was performed with catalytic amount of chiral BINOL derived phosphoric acid diester and Hantzsch dihydropyridine as hydrogen source providing the desired products in good yields and with excellent enantioselectivities.

This article is from Beilstein Journal of Organic Chemistry , volume 9 . Abstract A continuous-flow asymmetric organocatalytic photocyclization–transfer hydrogenation cascade reaction has been developed. The new protocol allows the synthesis of tetrahydroquinolines from readily available 2-aminochalcones using a combination of photochemistry and asymmetric Brønsted acid catalysis. The photocylization and subsequent reduction was performed with catalytic amount of chiral BINOL derived phosphoric acid diester and Hantzsch dihydropyridine as hydrogen source providing the desired products in good yields and with excellent enantioselectivities.

This article is from Beilstein Journal of Organic Chemistry , volume 9 . Abstract A continuous-flow asymmetric organocatalytic photocyclization–transfer hydrogenation cascade reaction has been developed. The new protocol allows the synthesis of tetrahydroquinolines from readily available 2-aminochalcones using a combination of photochemistry and asymmetric Brønsted acid catalysis. The photocylization and subsequent reduction was performed with catalytic amount of chiral BINOL derived phosphoric acid diester and Hantzsch dihydropyridine as hydrogen source providing the desired products in good yields and with excellent enantioselectivities.

This article is from Beilstein Journal of Organic Chemistry , volume 8 . Abstract The first decarboxylative Mannich reaction employing β-keto acids, catalyzed by cinchonine-derived bifunctional thiourea catalyst has been described. The desired β-amino ketones were obtained in excellent yields and with moderate to good enantioselectivities.

This article is from Beilstein Journal of Organic Chemistry , volume 9 . Abstract An enantioselective synthesis of the core framework of neurotrophic Illicium majucin-type sesquiterpenes is described here. This strategy is based on an organocatalyzed asymmetric Robinson annulation and provides an efficient approach for a diversity-oriented synthesis of Illicium natural products that holds remarkable therapeutic potential for neurodegenerative diseases.

This article is from Beilstein Journal of Organic Chemistry , volume 8 . Abstract For the first time, chiral sulfoximine derivatives have been applied as asymmetric organocatalysts. In combination with a thiourea-type backbone the sulfonimidoyl moiety leads to organocatalysts showing good reactivity in the catalytic desymmetrization of a cyclic meso-anhydride and moderate enantioselectivity in the catalytic asymmetric Biginelli reaction. Straightforward synthetic routes provide the newly designed thiourea-sulfoximine catalysts in high overall yields without affecting the stereohomogeneity of the sulfur-containing core fragment.

This article is from Beilstein Journal of Organic Chemistry , volume 8 . Abstract For the first time, chiral sulfoximine derivatives have been applied as asymmetric organocatalysts. In combination with a thiourea-type backbone the sulfonimidoyl moiety leads to organocatalysts showing good reactivity in the catalytic desymmetrization of a cyclic meso-anhydride and moderate enantioselectivity in the catalytic asymmetric Biginelli reaction. Straightforward synthetic routes provide the newly designed thiourea-sulfoximine catalysts in high overall yields without affecting the stereohomogeneity of the sulfur-containing core fragment.

We have previously observed the magnetite plaquettes in carbonaceous chondrites using scanning electron microscope (SEM) imaging, examined the crystal orientation of the polished surfaces of magnetite plaquettes in CI Orgueil using electron backscattered diffraction (EBSD) analysis, and concluded that these magnetite plaquettes are likely naturally asymmetric materials. In this study, we expanded our EBSD observation to other magnetite plaquettes in Orgueil, and further examined the internal structure of these remarkable crystals with the use of X-ray computed microtomography.

xiii,578p. : 24 cm

This invention relates to processes for preparing asymmetrical biphenyl tetracarboxylic acids and the corresponding asymmetrical dianhydrides, namely 2,3,3',4'-biphenyl dianhydride (a-BPDA), 2,3,3',4'-benzophenone dianhydride (a-BTDA) and 3,4'-methylenediphthalic anhydride (-MDPA). By cross-coupling reactions of reactive metal substituted o-xylenes or by cross-coupling o-xylene derivatives in the presence of catalysts, this invention specifically produces asymmetrical biphenyl intermediates that are subsequently oxidized or hydrolyzed and oxidized to provide asymmetric biphenyl tetracarboxylic acids in comparatively high yields. These asymmetrical biphenyl tetracarboxylic acids are subsequently converted to the corresponding asymmetrical dianhydrides without contamination by symmetrical biphenyl dianhydrides.

This invention relates to processes for preparing asymmetrical biphenyl tetracarboxylic acids and the corresponding asymmetrical dianhydrides, namely 2,3,3',4'-biphenyl dianhydride (a-BPDA), 2,3,3',4'-benzophenone dianhydride (a-BTDA) and 3,4'-methylenediphthalic anhydride (-MDPA). By cross-coupling reactions of reactive metal substituted o-xylenes or by cross-coupling o-xylene derivatives in the presence of catalysts, this invention specifically produces asymmetrical biphenyl intermediates that are subsequently oxidized or hydrolyzed and oxidized to provide asymmetric biphenyl tetracarboxylic acids in comparatively high yields. These asymmetrical biphenyl tetracarboxylic acids are subsequently converted to the corresponding asymmetrical dianhydrides without contamination by symmetrical biphenyl dianhydrides.

The process of protein synthesis in biological systems resembles a one dimensional driven lattice gas in which the particles have spatial extent, covering more than one lattice site. We expand the well studied Totally Asymmetric Exclusion Process (TASEP), in which particles typically cover a single lattice site, to include cases with extended objects. Exact solutions can be determined for a uniform closed system. We analyze the uniform open system through two approaches. First, a continuum limit produces a modified diffusion equation for particle density profiles. Second, an extremal principle based on domain wall theory accurately predicts the phase diagram and currents in each phase. Finally, we briefly consider approximate approaches to a non-uniform open system with quenched disorder in the particle hopping rates and compare these approaches with Monte Carlo simulations.

This article is from Beilstein Journal of Organic Chemistry , volume 10 . Abstract A new approach to the anticancer drug Velcade was developed by performing asymmetric borylation of an imine anchored with a chiral N-phosphinyl auxiliary. Throughout the 7-step synthesis, especially in the imine’s synthesis and in the asymmetric borylation reactions, operations and work-up were conducted in simple and easy ways without any column chromatographic purification, which defines the GAP (group-assisted purification) chemistry concept. It was found that the optically pure isomer (dr > 99:1) can be readily obtained by washing the crude mixture of the asymmetric borylation reaction with hexane; the chiral N-phosphinyl auxiliary can be easily recovered after deprotection is finished. Several other N-phosphinylimines were also investigated for the asymmetric borylation reaction. The absolute configuration of the borylation product was confirmed by single crystal X-ray diffraction analysis.

This article is from Beilstein Journal of Organic Chemistry , volume 9 . Abstract The enantioselective tandem Friedel–Crafts alkylation/Michael addition reaction of indoles with nitroolefin enoates catalyzed by a diphenylamine-linked bis(oxazoline)-Zn(OTf)2 complex was investigated. This tandem reaction afforded functionalized chiral chromans in good yields with moderate to high stereoselectivities (up to 95:5 dr, up to 99% ee).

This article is from Beilstein Journal of Organic Chemistry , volume 8 . Abstract A novel route to asymmetric synthesis of cinacalcet hydrochloride by the application of (R)-tert-butanesulfinamide and regioselective N-alkylation of the naphthyl ethyl sulfinamide intermediate is described.

This article is from Beilstein Journal of Organic Chemistry , volume 8 . Abstract A novel route to asymmetric synthesis of cinacalcet hydrochloride by the application of (R)-tert-butanesulfinamide and regioselective N-alkylation of the naphthyl ethyl sulfinamide intermediate is described.

Principles And Applications Of Asymmetric Synthesis

Principles And Applications Of Asymmetric Synthesis

Principles And Applications Of Asymmetric Synthesis

Principles And Applications Of Asymmetric Synthesis

This article is from Beilstein Journal of Organic Chemistry , volume 10 . Abstract A variety of chiral N-phosphinyl α-imino esters have been synthesized for the first time from ketoesters and phosphinylamide, which were then reduced by L-selectride to give the corresponding N-phosphinyl-protected α-amino esters. The reduction proceeded very well with excellent chemical yields (88–98%) as well as high diastereoselectivities (96:4 to 99:1). Some of these products could be obtained without column chromatography and recrystallization. The chiral phosphinyl auxiliary could be easily cleaved under acidic conditions.

This article is from Beilstein Journal of Organic Chemistry , volume 9 . Abstract The stereoselective Diels–Alder reaction between an optically active 1,4-dimethylcycloheptadiene and acrolein was effectively promoted by TBSOTf to produce a bicyclo[3.2.2]nonene derivative bearing two quaternary carbons. Seven additional transformations from the obtained bicycle delivered the C2-symmetric bicyclo[3.3.2]decene derivative, a key intermediate in our synthetic study of ryanodine.

This article is from Diabetes , volume 62 . Abstract We tested the effects of insulin on production of nitrous oxide (NO)-related substances (nitrites and nitrates [NOx]) after 15N-arginine intravenous infusion and on asymmetric dimethylarginine (ADMA) and symmetric dimethylarginine (SDMA) concentrations in conditions reportedly associated with altered NO availability, i.e., aging, hypertension, hypercholesterolemia, and type 2 diabetes mellitus (T2DM). A total of 26 male subjects (age 23–71 years, BMI 23–33 kg/m2), some of whom were affected by mixed pathologic features, were enrolled. NOx fractional synthesis rate (FSR) was lower in elderly (P < 0.015) and T2DM subjects (P < 0.03) than in matched control subjects. Hyperinsulinemia generally increased both NOx FSR and absolute synthesis rate (ASR) and reduced NOx, ADMA, and SDMA concentrations. Insulin sensitivity was impaired only in T2DM. With use of simple linear regression analysis across all subjects, age was inversely correlated with both NOx FSR (R2 = 0.23, P < 0.015) and ASR (R2 = 0.21, P < 0.02). NOx FSR inversely correlated with both ADMA and SDMA. With use of multiple regression analysis and various models, NOx FSR remained inversely associated with age and ADMA, whereas ASR was inversely associated with age and diabetes. No association with insulin sensitivity was found. We conclude that whole-body NOx production is decreased in aging and T2DM. Age, ADMA concentration, and T2DM, but not insulin resistance, appear as negative regulators of whole-body NOx production.

This article is from Beilstein Journal of Organic Chemistry , volume 10 . Abstract An efficient Ugi three-component reaction of a preformed chiral ketimine derived from isatin with various isonitrile and acid components has been developed. The reactions proceeded smoothly and in a stereocontrolled manner with regard to the new center of the Ugi products due to the stereoinduction of the amine chiral residue. A wide variety of novel chiral 3,3-disubstituted 3-aminooxindoles were obtained, a selection of which were subjected to post-Ugi transformations, paving the way to application as peptidomimetics.

This article is from Beilstein Journal of Organic Chemistry , volume 10 . Abstract An efficient Ugi three-component reaction of a preformed chiral ketimine derived from isatin with various isonitrile and acid components has been developed. The reactions proceeded smoothly and in a stereocontrolled manner with regard to the new center of the Ugi products due to the stereoinduction of the amine chiral residue. A wide variety of novel chiral 3,3-disubstituted 3-aminooxindoles were obtained, a selection of which were subjected to post-Ugi transformations, paving the way to application as peptidomimetics.

Book Source: Digital Library of India Item 2015.219802 dc.contributor.author: Ritchie,patrick D. dc.date.accessioned: 2015-07-09T21:26:17Z dc.date.available: 2015-07-09T21:26:17Z dc.date.digitalpublicationdate: 2005-05-17 dc.date.citation: 1933 dc.identifier.barcode: 2990140053703 dc.identifier.origpath: /data_copy/upload/0053/708 dc.identifier.copyno: 1 dc.identifier.uri: http://www.new.dli.ernet.in/handle/2015/219802 dc.description.scannerno: 10 dc.description.scanningcentre: Osmania University dc.description.main: 1 dc.description.tagged: 0 dc.description.totalpages: 174 dc.format.mimetype: application/pdf dc.language.iso: English dc.publisher.digitalrepublisher: Digital Library Of India dc.publisher: Oxford University Press. dc.rights: Not Available dc.source.library: Osmania University dc.subject.classification: Natural Sciences dc.subject.classification: Chemistry. Crystallography. Mineralogy dc.subject.classification: Practical Laboratory Chemistry. Preparative And Experimental Chemistry dc.title: Asymmetric Synthesis And Asymmetric Induction

Book Source: Digital Library of India Item 2015.194134 dc.contributor.author: M.v.r. Reddy dc.date.accessioned: 2015-07-08T04:00:10Z dc.date.available: 2015-07-08T04:00:10Z dc.date.digitalpublicationdate: 0000-00-00 dc.identifier.barcode: 1990010092396 dc.identifier.origpath: /rawdataupload/upload/0092/396 dc.identifier.copyno: 1 dc.identifier.uri: http://www.new.dli.ernet.in/handle/2015/194134 dc.description.scanningcentre: IIIT, Allahabad dc.description.main: 1 dc.description.tagged: 0 dc.description.totalpages: 293 dc.format.mimetype: application/pdf dc.language.iso: English dc.rights: Out_of_copyright dc.source.library: I I T Kanpur dc.subject.classification: Camical dc.subject.classification: Engineering. Technology In General dc.subject.classification: Chemistry dc.title: Studies In Asymmetric Synthesis Using

Book Source: Digital Library of India Item 2015.194134 dc.contributor.author: M.v.r. Reddy dc.date.accessioned: 2015-07-08T04:00:10Z dc.date.available: 2015-07-08T04:00:10Z dc.date.digitalpublicationdate: 0000-00-00 dc.identifier.barcode: 1990010092396 dc.identifier.origpath: /rawdataupload/upload/0092/396 dc.identifier.copyno: 1 dc.identifier.uri: http://www.new.dli.ernet.in/handle/2015/194134 dc.description.scanningcentre: IIIT, Allahabad dc.description.main: 1 dc.description.tagged: 0 dc.description.totalpages: 293 dc.format.mimetype: application/pdf dc.language.iso: English dc.rights: Out_of_copyright dc.source.library: I I T Kanpur dc.subject.classification: Camical dc.subject.classification: Engineering. Technology In General dc.subject.classification: Chemistry dc.title: Studies In Asymmetric Synthesis Using

Book Source: Digital Library of India Item 2015.194134 dc.contributor.author: M.v.r. Reddy dc.date.accessioned: 2015-07-08T04:00:10Z dc.date.available: 2015-07-08T04:00:10Z dc.date.digitalpublicationdate: 0000-00-00 dc.identifier.barcode: 1990010092396 dc.identifier.origpath: /rawdataupload/upload/0092/396 dc.identifier.copyno: 1 dc.identifier.uri: http://www.new.dli.ernet.in/handle/2015/194134 dc.description.scanningcentre: IIIT, Allahabad dc.description.main: 1 dc.description.tagged: 0 dc.description.totalpages: 293 dc.format.mimetype: application/pdf dc.language.iso: English dc.rights: Out_of_copyright dc.source.library: I I T Kanpur dc.subject.classification: Camical dc.subject.classification: Engineering. Technology In General dc.subject.classification: Chemistry dc.title: Studies In Asymmetric Synthesis Using

Book Source: Digital Library of India Item 2015.194134 dc.contributor.author: M.v.r. Reddy dc.date.accessioned: 2015-07-08T04:00:10Z dc.date.available: 2015-07-08T04:00:10Z dc.date.digitalpublicationdate: 0000-00-00 dc.identifier.barcode: 1990010092396 dc.identifier.origpath: /rawdataupload/upload/0092/396 dc.identifier.copyno: 1 dc.identifier.uri: http://www.new.dli.ernet.in/handle/2015/194134 dc.description.scanningcentre: IIIT, Allahabad dc.description.main: 1 dc.description.tagged: 0 dc.description.totalpages: 293 dc.format.mimetype: application/pdf dc.language.iso: English dc.rights: Out_of_copyright dc.source.library: I I T Kanpur dc.subject.classification: Camical dc.subject.classification: Engineering. Technology In General dc.subject.classification: Chemistry dc.title: Studies In Asymmetric Synthesis Using

Book Source: Digital Library of India Item 2015.194134 dc.contributor.author: M.v.r. Reddy dc.date.accessioned: 2015-07-08T04:00:10Z dc.date.available: 2015-07-08T04:00:10Z dc.date.digitalpublicationdate: 0000-00-00 dc.identifier.barcode: 1990010092396 dc.identifier.origpath: /rawdataupload/upload/0092/396 dc.identifier.copyno: 1 dc.identifier.uri: http://www.new.dli.ernet.in/handle/2015/194134 dc.description.scanningcentre: IIIT, Allahabad dc.description.main: 1 dc.description.tagged: 0 dc.description.totalpages: 293 dc.format.mimetype: application/pdf dc.language.iso: English dc.rights: Out_of_copyright dc.source.library: I I T Kanpur dc.subject.classification: Camical dc.subject.classification: Engineering. Technology In General dc.subject.classification: Chemistry dc.title: Studies In Asymmetric Synthesis Using

Book Source: Digital Library of India Item 2015.194134 dc.contributor.author: M.v.r. Reddy dc.date.accessioned: 2015-07-08T04:00:10Z dc.date.available: 2015-07-08T04:00:10Z dc.date.digitalpublicationdate: 0000-00-00 dc.identifier.barcode: 1990010092396 dc.identifier.origpath: /rawdataupload/upload/0092/396 dc.identifier.copyno: 1 dc.identifier.uri: http://www.new.dli.ernet.in/handle/2015/194134 dc.description.scanningcentre: IIIT, Allahabad dc.description.main: 1 dc.description.tagged: 0 dc.description.totalpages: 293 dc.format.mimetype: application/pdf dc.language.iso: English dc.rights: Out_of_copyright dc.source.library: I I T Kanpur dc.subject.classification: Camical dc.subject.classification: Engineering. Technology In General dc.subject.classification: Chemistry dc.title: Studies In Asymmetric Synthesis Using

This article is from Beilstein Journal of Organic Chemistry , volume 9 . Abstract A chiral phosphoric acid-catalyzed selenofunctionalization of tryptamine derivatives provides access to 3a-(phenylselenyl)-1,2,3,3a,8,8a-hexahydropyrrolo[2,3-b]indole derivatives in high yields and with synthetically useful levels of enantioselectivity (up to 89% ee).

This article is from Beilstein Journal of Organic Chemistry , volume 9 . Abstract Asymmetric alkylation reactions using non-cross-linked polystyrene (NCPS)-supported 2-imidazolidinone chiral auxiliaries were successfully investigated with excellent diastereocontrol (>99% de). The recovery and the recycling of this soluble polymer-supported chiral auxiliary were achieved in order to produce highly optical pure carboxylic acids.

In the article group-theoretical approach for analysis and synthesis of asymmetric images is considered. Methods and algorithms of analysis and synthesis of asymmetric images are offered. For software implementation of the offered algorithms the integrated development environment Visual C++ Express Edition and opened library of functions of computer vision Open CV is used.