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Monosakkariede as uitgangstowwe vir die sintese van heterosikliese prostaglandienanaloë25 November 2014 (has links)
D.Sc. / Please refer to full text to view abstract
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Genetics of abequose biosynthesis in the rfb region of Salmonella typhimurium LT2 /Wyk, Paul. January 1988 (has links) (PDF)
Thesis (Ph. D.)--University of Adelaide, 1989. / Includes bibliographical references.
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A contribution to the chemistry of xyloseSpeedie, Thomas Hall January 1934 (has links)
No description available.
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Synthesis of higher carbohydrates and iminosugars on dioxanone scaffoldPalyam, Nagarjuna 02 July 2010
Dioxanones (1) are ketal- or acetal protected forms of 1,3-dihydroxyacetone (DHA). The thesis presents the stereoselective aldol transformations of dioxanones and applications to the synthesis of natural and higher carbohydrates listed in Scheme 1.<p>
The field of organocatalysis has recently gained much popularity among the chemical research community. In our group, a set of conditions are developed to perform stereoselective aldol reactions on dioxanone substrate. Cs-symmetrical dioxanones have superior diasteroselectivities than C2v-symmetrical dioxanones (de up to 88% from 34%) and presence of mild Lewis acid (LiCl) or Brønsted acid additives (PyPTS) enhance the enantioselectivity into synthetically useful ranges (from 60 up to 96 % ee).<p>
The first aldol addition of dioxanone (1) to desired aldehydes (possessing masked carbonyl functionality), followed by reduction of the corresponding aldol adduct and upon unmasking the aldehyde functionality (i.e dithiane or dimethoxy acetal hydrolysis) resulted in furanose (II) and pyranose (III) forms of D-ribose.<p>
A new protocol was developed for the synthesis of biologically important deoxyiminosugars such as L-1-deoxymannojirimycin (DMJ, IV), L-1-deoxyidonojirimycin (DIJ, V) and N-isopropyl DIJ (IV) from readily available dioxanone (1) precursor. The key steps include diastereoselective proline-catalyzed syn-aldol transformation and a reductive amination / cyclization.<p>
D-glycero-D-manno-2-octulose (VII), a higher-carbon sugar isolated from opium poppies has been synthesized in enantiomerically pure form. The short synthetic sequence involved two proline-catalyzed aldol addition reactions of dioxanone (1) to appropriate aldehydes. Here, we developed a complete dioxanone methodology towards the higher monosaccharide in a stereocontrolled fashion.<p>
The enantioselective stereodivergent first total synthesis of DD- and LL-glycero-β-alloheptopyranose (IX, ent-IX) was accomplished from readily available non-chiral starting materials. The short synthetic sequence involves enamine and enolate mediated aldol reactions at α and α' positions of dioxanone (1) hence demonstrated the complementary nature of organocatalysis and organometallic methods.
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Synthesis of higher carbohydrates and iminosugars on dioxanone scaffoldPalyam, Nagarjuna 02 July 2010 (has links)
Dioxanones (1) are ketal- or acetal protected forms of 1,3-dihydroxyacetone (DHA). The thesis presents the stereoselective aldol transformations of dioxanones and applications to the synthesis of natural and higher carbohydrates listed in Scheme 1.<p>
The field of organocatalysis has recently gained much popularity among the chemical research community. In our group, a set of conditions are developed to perform stereoselective aldol reactions on dioxanone substrate. Cs-symmetrical dioxanones have superior diasteroselectivities than C2v-symmetrical dioxanones (de up to 88% from 34%) and presence of mild Lewis acid (LiCl) or Brønsted acid additives (PyPTS) enhance the enantioselectivity into synthetically useful ranges (from 60 up to 96 % ee).<p>
The first aldol addition of dioxanone (1) to desired aldehydes (possessing masked carbonyl functionality), followed by reduction of the corresponding aldol adduct and upon unmasking the aldehyde functionality (i.e dithiane or dimethoxy acetal hydrolysis) resulted in furanose (II) and pyranose (III) forms of D-ribose.<p>
A new protocol was developed for the synthesis of biologically important deoxyiminosugars such as L-1-deoxymannojirimycin (DMJ, IV), L-1-deoxyidonojirimycin (DIJ, V) and N-isopropyl DIJ (IV) from readily available dioxanone (1) precursor. The key steps include diastereoselective proline-catalyzed syn-aldol transformation and a reductive amination / cyclization.<p>
D-glycero-D-manno-2-octulose (VII), a higher-carbon sugar isolated from opium poppies has been synthesized in enantiomerically pure form. The short synthetic sequence involved two proline-catalyzed aldol addition reactions of dioxanone (1) to appropriate aldehydes. Here, we developed a complete dioxanone methodology towards the higher monosaccharide in a stereocontrolled fashion.<p>
The enantioselective stereodivergent first total synthesis of DD- and LL-glycero-β-alloheptopyranose (IX, ent-IX) was accomplished from readily available non-chiral starting materials. The short synthetic sequence involves enamine and enolate mediated aldol reactions at α and α' positions of dioxanone (1) hence demonstrated the complementary nature of organocatalysis and organometallic methods.
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Functional characterization of hexokinases in the moss Physcomitrella patens /Olsson, Tina, January 2005 (has links) (PDF)
Diss. (sammanfattning) Uppsala : Sveriges lantbruksuniversitet, 2005. / Härtill 3 uppsatser.
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Sintetiese metodes vir die regioselektiewe funksionalisering van monosakkariedeSwanepoel, Anna Dorathea 12 March 2014 (has links)
Ph.D. (Chemistry) / The aim of this study was the development of stereoselective routes for the asymmetric synthesis of chiral precursors of I1-deoxy-1l-thiaprostaglandins and albomysin di, using carbohydrates as chiral building blocks. A brief overview of known stereocontrolled routes for the synthesis of sulphur-containing monosaccharides and heterocyclic prostaglandin analogues is presented. Approaches to the stereocontrolled synthesis of I1-deoxy-11-thiaprostaglandins from Larabinose are described. Special topics in this part of the study include approaches to the preparation of chiral tetrahydrothiophenes. The 1,4-diol 5-0-benzoyl-3-deoxy-3-C-(carboxymethyl- 2,3-y-lactone)-L-lyxitol (146a), was identified as a possible chiral building block for the proposed route towards 11-thiaprostaglandins. New groups for the activation of the hydroxyl functions of the 1,4-diol in order to introduce the ring sulphur atom via a 1thiobenzyl ether, were investigated. The l,4-diol was subsequently transformed into a 1,4dimesylate and this compound proved to be the most suitable for the generation of the tetrahydrothiophene unit. This investigation resulted in an efficient synthesis of 11thiaprostaglandin precursors using glucose as a chiral building block. In the second part of the investigation, approaches to the stereoselective synthesis of a potential precursor for the synthesis of albomysin dr are described. An investigation of the selective acylation of acyclic pentoses are also presented. The aim of this study was the regioselective introduction of a leaving group, for example a tosylate, in acyclic derivatives of pentose without protecting any of the secondary hydroxyl groups. This strategy would make intramolecular cyclisations possible with a suitable nycleophile present on C-l. Some of the compounds in the pentose series investigated, furnished dibutyltin complexes which were regioselectively acylated in an efficient manner. Starting from L-arabinose an alternative strategy for the synthesis of a precursor for the synthesis of aIbomysin di is also given. The synthesis involved the preparation of 1-0-acetyl2,3, 5-tri-O-benzoyl-4-thio-xylofuranose, followed by conversion to the required nucleoside.
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Studies Toward the Synthesis of Aminosugars Related to Components of the S. aureus Capsular PolysaccharideFluxe, Andrew James 14 December 2001 (has links)
No description available.
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The effect of monosaccharide reducing sugars on the atom transfer radical polymerization of n-butyl methacrylate and methyl methacrylateDe Vries, Andrew Robert 12 1900 (has links)
Thesis (MSc)--Stellenbosch University, 2001 / ENGLISH ABSTRACT: The effect of various organic reducing agents, in the. form of monosaccharide reducing sugars, on the
rate of atom transfer radical polymerization (ATRP) of n-butyl methacrylate and methyl methacrylate is
reported in this study. The addition of the reducing sugars has a positive effect on the rate of ATRP. Up
to 100% increase in the rate of polymerization was recorded, in some cases. These organic reducing
agents have little effect on the molecular weight and molecular weight distribution of the polyin-butyl
methacrylate) and polydispersity indexes remain well below 1.2. The molecular weight of the
poly(methyl methacrylate), when glucose and galactose are added to the reaction mixture, compares
well with the theoretical expected values.
An explanation for these observations is the ability of the reducing sugars to reduce part of the Cu(II)
species, that serves to deactivate the growing radicals, to Cu(I), thereby ensuring a shift in the
equilibrium between active and dormant chains in the direction of the former and a resulting increase in
the rate of polymerization.
uvNIS spectroscopy and cyclic voltammetry were used to investigate the mechanism behind the
polymerization rate enhancement. / AFRIKAANSE OPSOMMING: In hierdie studie word die effek van verskeie organiese reduseermiddels, in die vorm van monosakkaried
reduserende suikers, op die tempo van polimerisasie van ATRP gerapporteer. Hierdie reduserende
suikers het 'n positiewe effek op die polimerisasie tempo. In sommige gevalle word 'n toename van
100% in die polimerisasie tempo waargeneem. Die organiese reduseermiddels het 'n minimale effek op
die molekulere massa en molekulere massa verspreiding (in meeste gevalle minder as 1.2) van die
poly(n-butiel metakrielaat). In die geval van die poly(metiel metakrielaat), wanneer glukose en
galaktose by die reaksie mengsel gevoeg word, stem die molekulere massas goed ooreen met die
teoreties voorspelde molekulere massas.
Die waargenome toename in die polimerisasie tempo kan toegeskryf word aan die vermoe van die
reduserende suikers om die Cu(II), wat dien om die groeiende radikale te deaktiveer, gedeeltelik te
reduseer na Cu(l). Hierdeur word verseker dat die ewewig tussen die aktiewe en dormante kettings in
die rigting van die eersgenoemde verskuif word, wat dus aanleiding gee tot 'n toename in die
polimerisasie tempo.
Ultraviolet spektroskopie en sikliese voltammetrie is ook gebruik om lig te werp op die meganisme agter
die toename in die tempo van polimerisasie.
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Structural studies of glyceraldehyde-3-phosphate dehydrogenase complexes and the E. coli PutA DNA binding domainJenkins, Jermaine L., January 2006 (has links)
Thesis (Ph.D.)--University of Missouri-Columbia, 2006. / The entire dissertation/thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file (which also appears in the research.pdf); a non-technical general description, or public abstract, appears in the public.pdf file. Title from title screen of research.pdf file (viewed on April 27, 2009) Vita. Includes bibliographical references.
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