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Dissertations / Theses on the topic 'Diastereoselective'

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Published: 4 June 2021
Last updated: 1 February 2022

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1

Aciro, Caroline. "Diastereoselective olefin dihydroxylations." Thesis, University of Oxford, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.496817.

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2

BRASSEUR, DENIS. "Carbometallation diastereoselective d'olefines metallees." Paris 6, 1998. http://www.theses.fr/1998PA066045.

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La carbometallation d'olefines metallees deja decrite au laboratoire a ete etendue a des substrats azotes et soufres. Puis une extension en serie optiquement enrichie a ete developpee en utilisant comme pool chiral des derives de l'ephedrine, d'amino acides naturels, de diamines vicinales et de derives aromatiques. Enfin une nouvelle reaction de propargylzincation intermoleculaire a ete decrite.
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3

Walker, Matthew David. "Diastereoselective reactions of atropisomeric lactams." Thesis, University of Nottingham, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.247569.

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4

Standen, Stephen P. "The diastereoselective synthesis of phenylsulfonyloxiranes." Thesis, University of Newcastle Upon Tyne, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.332245.

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5

Walford, Steven Paul. "Diastereoselective synthesis of peptide mimetics." Thesis, University of Bath, 1992. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.760630.

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6

PONSINET, RACHEL. "Synthese diastereoselective d'acides beta-amines." Paris 6, 1999. http://www.theses.fr/1999PA066411.

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Si de nombreuses publications decrivent la synthese enantioselective d'acides -amines substitues en de la fonction acide (acides 3-amines) ou disubstitues en et , peu en revanche, concernent la synthese d'acides -amines uniquement substitues en (acides 2-amines). La plus grande partie du travail decrit dans cette these est axee sur une nouvelle voie de synthese diastereoselective d'acides 2-amines. Pour cela, deux strategies ont ete etudiees : la premiere correspond a une carboxylation enantioselective en d'une fonction nitrile (precurseur de la fonction amine). Elle est basee sur l'utilisation d'un electrophile chiral, obtenu par action du triphosgene sur le sultame d'oppolzer, et a conduit a la 2-phenylglycine enantiomeriquement pure. Mais elle n'est pas applicable a la synthese d'autres acides 2-amines a chaines laterales carbonees. La deuxieme strategie est basee sur l'alkylation d'un precurseur chiral derive de la -alanine. L'introduction de la chaine laterale de l'acide amine souhaite se fait avec une stereochimie induite par l'auxiliaire chiral : le sultame d'oppolzer. Cette strategie a permis d'obtenir la 2-phenylalanine, la 2-alanine et la 2-leucine avec d'excellents exces enantiomeriques. Elle necessite l'utilisation d'agents alkylants reactifs a basse temperature pour eviter l'elimination de l'enolate. Des etudes preliminaires portant sur l'introduction de chaines laterales fonctionnalisees (telles que celles de la lysine, de la methionine ou de l'acide aspartique) ont ete engagees, elles seront poursuivies. Les acides 2-amines aromatiques obtenus suivant ces deux strategies ont ete introduits dans la sequence de la substance p. Ces premiers analogues se sont averes etre peu affins et peu actifs. Une autre partie de ce travail a porte sur la mise au point d'une voie de synthese d'acides 3-amines (en particulier la 3-alanine) a partir de l'acide aspartique, en vue d'une application a grande echelle.
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7

Romine, Jeffrey Lee. "A diastereoselective approach to ikarugamycin /." The Ohio State University, 1987. http://rave.ohiolink.edu/etdc/view?acc_num=osu1487329662146093.

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8

Cariou, Claire. "Diastereoselective synthesis of 2,4,5-trisubstituted piperidines." Thesis, University of Birmingham, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.434701.

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9

Tunstall, James Christopher. "Diastereoselective cycloadditions of isothiazolone S-oxides." Thesis, University of Leeds, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.446056.

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10

Marsault, Eric. "Diastereoselective synthesis of phosphite triesters and phosphorothioates." Thesis, McGill University, 1996. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=42091.

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The diastereoselective synthesis of phosphite triesters and related phosphorothioate triesters and diesters has been investigated, with the goal of synthesizing diastereomerically pure DNA phosphorothioates.
Towards this end, the elaboration of a new heterobicyclic structure, imidazo-oxazaphosphorine such as 56, is reported. This unstable intermediate led to the highly diastereoselective synthesis of simple phosphite triesters upon reaction with various alcohols.
Two new types of sterically hindered chiral oxazaphosphorinanes 135 and 146 were then synthesized from cholesterol and camphor respectively. These structures, derived from $ gamma$-aminoalcohols possessing a tertiary alcohol function, could be isolated and characterized. They revealed very reactive in acidic conditions and led to rearrangements.
Finally, oxazaphosphorinane 188 derived from 1,2-O-isopropylidene-D-xylofuranose, was synthesized and characterized. The introduction of a participating group adjacent to the leaving phosphorothioate group led to the fast release of the phosphorothioate moiety. This new chiral auxiliary was successfully used as a precursor in the diastereoselective synthesis of a T-T phosphorothioate dimer, in a diastereomeric ratio of 28.5:1.* ftn*Please refer to dissertation for diagrams.
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11

Marsault, Eric. "Diastereoselective synthesis of phosphite triesters and phosphorothioates." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk2/tape16/PQDD_0027/NQ30333.pdf.

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12

Steukers, Veronique Gerarda Remy. "Enantio- and diastereoselective transformations catalysed by lipases." Thesis, University of Exeter, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.357975.

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13

Kilburn, J. D. "Diastereoselective aldol reactions of #beta#-silyl enolates." Thesis, University of Cambridge, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.377832.

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14

Dema, Haythem Karim. "Chiral aldimines in diastereoselective carbon nucleophile additions." Doctoral thesis, Universidad de Alicante, 2012. http://hdl.handle.net/10045/27136.

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15

Caya, Thomas Charles. "Diastereoselective, Alkoxide-Directed Diborations of Alkenyl Alcohols." Thesis, Boston College, 2014. http://hdl.handle.net/2345/3859.

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Thesis advisor: James P. Morken
The metal-catalyzed diboration of alkenes has gained fame as a practical methodology for use in the stereoselective construction of complex organic molecules and synthetic building blocks. The created carbon-boron bonds have tremendous versatility and can easily be manipulated into carbon-carbon or carbon-heteroatom bonds. Unfortunately, metal-catalyzed diborations often suffer from limitations such as substrate specificity. To address these issues, we investigated diboration reactions in the absence of transition-metal catalysts. Herein is presented a transition-metal-free, diastereoselective diboration methodology utilizing alkenyl alcohols as substrates. Allylic alcohols can be treated with an organolithium base and bis(pinacolato)diboron to generate 1,2,3-triols upon oxidation. Most studies were done on homoallylic alcohols, which can be performed using a carbonate base and an alcohol additive. This methodology has many strengths, such as a wide substrate scope and high levels of diastereoselectivity. Further investigations into product functionalization and synthetic applications will be pursued in due time
Thesis (MS) — Boston College, 2014
Submitted to: Boston College. Graduate School of Arts and Sciences
Discipline: Chemistry
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16

Geoghan, Allison. "Regio- and Diastereoselective Hydroformylation of Homoallylic Alcohols." Thesis, Boston College, 2013. http://hdl.handle.net/2345/3233.

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Thesis advisor: Kian L. Tan
Scaffolding ligand, 14, was designed to direct the hydroformylation of 1,2 disubstituted alkenes, such that the aldehyde forms at the carbon distally from the directing group. The ligand has the ability to form reversible covalent bonds with the substrate and bind to the metal to achieve high conversion, regio- and diastereoselectivity of homoallylic alcohol products
Thesis (MS) — Boston College, 2013
Submitted to: Boston College. Graduate School of Arts and Sciences
Discipline: Chemistry
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17

O'Brien, Peter Andrew. "Enantio- and diastereoselective reactions with phosphine oxides." Thesis, University of Cambridge, 1995. https://www.repository.cam.ac.uk/handle/1810/271960.

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18

BONNE, FREDERIQUE. "Synthese enantio et diastereoselective d'amino hydroxy acides." Université Louis Pasteur (Strasbourg) (1971-2008), 1994. http://www.theses.fr/1994STR13181.

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Dans ce travail, nous avons mis au point une synthese d'amino alcools en cinq etapes, avec un rendement global de 50% et une excellente diastereoselectivite (> 95%). Un modele d'approche rendant compte de la diastereoselectivite (s,s) obtenue a ete propose. En appliquant cette methode, une nouvelle synthese de la (3s,4s) statine a ete tente. Seulement elle n'a pas pu etre realisee jusqu'au bout, la derniere etape consistant a introduire la fonction acide s'averant difficile. Toutefois cet intermediaire peut donner acces a divers amino alcools, amino thiols ou amino diols. Nous avons utilise la nitroaldolisation pour creer les 2 centres asymetriques (c#2 et c#3) par utilisation de bases fluores csf et kf. Nous avons ainsi synthetise les deux diastereomeres de la (2s,3s) allocyclohexylnorstatine et (2s,3r) cyclohexylnorstatine avec un rendement total 40% et 30% respectivement. Une synthese simple et efficace d'imines a ete mis au point a partir d'aldehydes (ou cetones) par utilisation du complexe d'amidure d'aluminium et de lithium lia1 (nhr)#4
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19

Fryling, James Allen 1959. "AN ENANTIOSELECTIVE SYNTHESIS OF BETA-EUDESMOL (DIASTEREOSELECTIVE, CYCLOPROPANATION)." Thesis, The University of Arizona, 1986. http://hdl.handle.net/10150/291680.

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20

Selva, Verónica. "Diastereoselective multicomponent [3+2] and [4+2] cycloadditions." Doctoral thesis, Universidad de Alicante, 2018. http://hdl.handle.net/10045/77573.

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En esta tesis doctoral se ha estudiado los iluros de azometino generados in situ en reacciones de cicloadición 1,3-dipolar y diferentes dipolarófilos para la síntesis multicomponente (libre de metales) de derivados de indolizidina a partir de pipecolinatos, aldehídos y dipolarofilos de forma térmica, y también a partir de ácido pipecólico de forma descarboxilada. También se ha estudiado la reacción de cicloadición 1,3-dipolar térmica multicomponente entre iluros de azometino no activados generados in situ a partir de aminas, aldehídos aromáticos y alquenos electrofílicos para generar derivados de pirrolidina.Además, se describe la síntesis de pirrolizidinas diastereoméricamente enriquecidas a partir de nitroprolinatos enantioméricamente puros a través de una cicloadición 1,3- dipolar multicomponente catalizada por una sal de plata y, por otro lado, una reacción de Amina-Aldehído-Dienófilo (AAD) para sintetizar estructuras ciclohex-2-en-1-ilprolinato como diastereoisómero enantiopuro único de forma multicomponente y libre de metales.
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21

AWANDI, DJAMSAH. "Photodeconjugaison diastereoselective de composes carbonyles alpha, beta-insatures." Reims, 1991. http://www.theses.fr/1991REIM5013.

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L'irradiation des esters chiraux alpha, beta-insatures alpha-substitues en presence d'une quantite catalytique d'une amine secondaire, ou d'un aminoalcool conduit, avec creation d'un nouveau carbone asymetrique, aux isomeres deconjugues. La variation de la nature de l'amine secondaire achirale a permis d'optimiser l'induction asymetrique. Des exces diastereoisomeriques de l'ordre de 90% ont ete obtenus en presence de diisopropylamine. La photodeconjugaison diastereoselective par protonation intramoleculaire du photodienol a ete realisee meme en absence d'un additif protique
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22

Perfetti, Michael Thomas. "Diastereoselective α-Alkylation of Chiral β-Borylated Esters." Thesis, Virginia Tech, 2009. http://hdl.handle.net/10919/30820.

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The use of boron in the synthesis and development of asymmetric methodologies and various biological and medicinal compounds has increased significantly over the last decade. This thesis reports the development of a novel diastereoselective reaction for the α-alkylation of chiral β-borylated esters. We propose that standard deprotonation of chiral β-borylated esters with lithium diisopropylamide (LDA) leads to the formation of a boron"ate" intermediate that upon treatment with an alkylation reagent collapses to provide chiral α, β-substituted boronic esters with a high degree of diastereoselectivity. This reaction is powerful in that a wide range of chiral β-borylated ester substrates can be employed that possess varying degrees of substitution and steric bulk. Results show that the reaction is syn-selective and provides yields of up to 60%, with diastereomeric ratios as high as (9.7:1). Additionally, alkylation products from bulkier tert-butyl esters provide higher DR values compared to those of methyl esters that possess the same β-functional groups. Several techniques were utilized to elucidate the mechanism of this reaction including variations of reaction temperature and equivalents of base, and also real-time analysis of the reaction by ¹¹B NMR experiments.
Master of Science
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23

Zhang, Xiao-An. "The diastereoselectivity of some novel organic reactions." Thesis, University of Bath, 1987. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.377963.

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24

Sebhat, Iyassu Kenneth. "Enantioselective deprotonation of arenetricarbonyl chromium complexes." Thesis, Imperial College London, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.243310.

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25

Sprague, Simon J. "Diastereoselective manganese(III) acetate-mediated synthesis of nitrogen-containing heterocyles." Thesis, University of Oxford, 2010. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.526434.

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26

Ebden, Mark Richard. "Regioselective, diastereoselective and enantioselective substitution reactions of amine-borane complexes." Thesis, University of Nottingham, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.243770.

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27

Abualnaj, Matoka h. Mohammed A. "Diastereoselective synthetic approaches to functionalised tetrahydropyrrolo[3,4-a] carbazole derivatives." Thesis, University of Newcastle upon Tyne, 2016. http://hdl.handle.net/10443/3265.

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The heterocyclic carbazoles are privileged scaffolds present in many biologically active naturally occurring and synthetic compounds. Herein, we disclose our investigations into new approaches towards the diastereoselective synthesis of highly functionalised tetrahydropyrrolo[3,4-a] carbazole derivatives, and the subsequent evaluation of their biological activities. Our synthetic methodology is based on an initial intermolecular Diels-Alder (D-A) reaction between a substituted 3-vinyl-1H-indole 1, containing an electron withdrawing N-protecting group, and a range of dienophiles. This key step allows access to a variety of the D-A cycloadducts 2 in good yields (64-85%) and as single diastereomers, arising from an endo selective D-A cycloaddition (Scheme 1). Scheme 1. D-A reaction of N-protected, substituted 3-vinyl-1H-indole 1 The new alkene bond generated in the D-A reaction is highly reactive towards electrophiles and has a propensity towards migration, to rearomatise the indole ring. Thus we decided to exploit this reactivity to generate our target pyrrolo[3,4-a]carbazoles using a number of different approaches (Scheme 2). Route 1: D-A cycloadducts 2 was further functionalised using an intermolecular ene reaction to afford the tetrahydropyrrolo[3,4-a]carbazoles 3. Route 2: Alternatively intramolecular carbonyl-ene reactions of D-A cycloadducts 2 were investigated as a route to polycyclic tetrahydropyrrolo[3,4-a]carbazoles 4. Route 3: Finally bromination of the reactive alkene followed by in situ trapping with a nucleophilic amines gave access to amine functionalised tetrahydropyrrolo[3,4-a]carbazoles 5. These could in turn be deprotected via a PtO2 catalysed hydrogenation to give a focussed library of biologically active molecules 6. Scheme 2. Synthetic approaches towards functionalised pyrrolo[3,4-a]carbazole.
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28

D'ANIELLO, FABIANA. "Synthese enantio- et diastereoselective d'acides amines au moyen de bromoallenes." Université Louis Pasteur (Strasbourg) (1971-2008), 1996. http://www.theses.fr/1996STR13017.

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La synthese diastereo- et enantioselective d'analogues d'acides amines a ete abordee. Nous avons montre que la configuration du stereocentre forme lors de l'alkylation d'un bromoallene par un reactif organometallique etait liee uniquement a la configuration de ce dernier sans interference d'un stereocentre voisin. Cette observation nous a permis de mettre en uvre une procedure generale de preparation d'acides amines -substitues a partir de serinal (l-isoleucine et l-alloisoleucine) et de realiser la synthese de l'adda acide (2s, 3s, 8s, 9s)-3-amino-9-methoxy-2,6,8-trimethyl-10-phenyldeca-4,6-dienoique a partir de l'acide l-phenyllactique. Ces deux syntheses ont en commun l'enchainement ch(x)-ch(me)-alcyne, accessible de maniere stereoselective par alkylation s#n2' d'un bromoallene. D'un point de vue mecanistique, nous avons egalement montre que les silabromoallenes et les bromoallenes ont un comportement complementaire vis a vis d'attaques nucleophiles. Dans le premier cas, on observe une reaction s#n2 et dans l'autre une reaction s#n2'. Notre travail montre que les bromoallenes, peu utilises jusqu'a present en synthese totale, sont des substrats fiables quand il s'agit de realiser des syntheses enantio- et diastereoselectives
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29

DeRussy, Donald Thomas. "Diastereoselective formation and stereocontrolled rearrangement of anionic oxy-cope precursors /." The Ohio State University, 1989. http://rave.ohiolink.edu/etdc/view?acc_num=osu1487671640054272.

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30

Simon, Meike [Verfasser], and Paul [Akademischer Betreuer] Knochel. "Diastereoselective intramolecular carbolithiation and acylation reactions / Meike Simon ; Betreuer: Paul Knochel." München : Universitätsbibliothek der Ludwig-Maximilians-Universität, 2018. http://d-nb.info/120987797X/34.

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31

Torok, Daniel Seth 1963. "Diastereoselective cyclopropanations of alpha,beta-unsaturated ketals derived from chiral hydrobenzoin." Thesis, The University of Arizona, 1988. http://hdl.handle.net/10150/276784.

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2-Cycloalken-1-one-(-)-erythro-hydrobenzoin ketals undergo efficient and diastereoselective cyclopropanation when treated with an excess of Simmons-Smith reagent. The resulting crystalline products yield enantiomerically pure cyclopropyl compounds upon recrystallization. For example, 2-cyclohexen-1-one-(-)-erythro-hydrobenzoin ketal gave, in 90% yield, a 19:1 mixture of diastereomeric cyclopropanes as established by 62.9 MHz ¹³C NMR spectroscopy. Upon one recrystallization, diastereomerically pure cyclopropane was obtained in 78% recovery. Hydrolysis gave (+)-norcaranone of greater than 99% ee. Three other examples are presented which demonstrate the advantages of hydrobenzoin ketals over previously used homochiral ketals, as well as several techniques for the synthesis of chiral hydrobenzoin.
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32

Samoshin, Andrey V. "Diastereoselective acylation of trans-2-substituted-cyclohexanols and glycosidase inhibition studies." Scholarly Commons, 2011. https://scholarlycommons.pacific.edu/uop_etds/275.

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Part I. The reaction between chiral acyl chlorides and trans -2-substituted-cyclohexanols proceeds diastereoselectively, i.e. produces mixtures of unequal amounts of diastereomers. We found for the first time that addition of pyridine or diisopropylethylamine accelerates the acylation, and unexpectedly for some substituents (RX) may completely invert its diastereoselectivity. These observations have been rationalized in terms of a stereoselective intramolecular assistance by the RX group to the acylation of the neighboring hydroxyl ("bait-and-hook" mechanism). A series of trans -2-substituted-cyclohexanols were synthesized and acylated with a racemic reagent in presence and absence of pyridine. The results showed that the presence of a nucleophilic group on the second carbon allowed for the preferred formation of one of the diastereomers in the absence of pyridine. However, in the presence of pyridine, the diastereoselectivity would inverse, and the reaction would favor the formation of the other diastereomer. To test the intramolecular acyl transfer hypothesis in detail a series of thioglucosides has been synthesized. Part II. The synthesized thioglucosides were tested as inhibitors of fungal glycosidases. Two compounds showed greater than 80% inhibition values in excess of the activity of β-D-glucosidases. More interestingly, the same compounds showed a marked enhancement of α-D-galactosidase activity by as much as 35%.
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33

Sadler, Matthew James. "Diastereoselective synthesis of 2,4,5 trisubstituted piperidines : application in natural product synthesis." Thesis, University of Birmingham, 2011. http://etheses.bham.ac.uk//id/eprint/2901/.

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This thesis describes the diastereoselective synthesis of 2,4,5-trisubstituted piperidines using carbonyl-ene and Prins cyclisations and their application in natural product synthesis. Following on from previous work in the group, we investigated how a preinstalled substituent in the 2-position can help to control the sense of induction at the two newly forming stereocentres. We utilised the Prins reaction in the formal synthesis of pseudodistomin F, a marine alkaloid that posses a 2,4,5-tribsubstituted piperidine core. An initial first generation synthesis focused on the construction of a cyclisation precursor containing a crotyl-ene component, however, cyclisation with anhydrous hydrogen chloride at -78 °C resulted in side product formation, presumably resulting from the relative instability of the secondary carbocation. Changing the ene component to a prenyl group resulted in successful cyclisation to yield the trans, cis-2,4,5-trisubstituted piperidine, with diastereomeric ratios of up to 200:1. An improved second generation synthesis completed the formal synthesis of pseudodistomin F on a multi-gram scale. Progress towards the total synthesis of pseudodistomin F by a third generation synthesis was undertaken. An investigation into how varying the electronics of the Prins reaction would alter the diastereoselectivity was conducted with a range of para-substituted cinnamyl substrates. The results indicated that selectivity in favour of the trans diastereomer was favoured as the electron withdrawing power of the substituent increased.
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34

LELONG, BRUNO. "Synthese diastereoselective de thioamides ' et -dihydroxyles : une voie d'acces aux valerolactones." Caen, 1997. http://www.theses.fr/1997CAEN2059.

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L'objectif de ce travail est l'hydroboration chimio- et diastereoselective de composes thiocarbonyles -insatures. Ces molecules sont en effet de bons precurseurs pour synthetiser des valerolactones de facon assez simple. Apres avoir montre que la reaction d'hydroboration n'est pas chimioselective vis a vis des dithioesters, et constate que la reaction d'hydroboration sur les dithiocetals -ethyleniques n'est pas diastereoselective, nous nous sommes tournes vers la fonction thioamide pour acceder aux lactones. Les -hydroxythioamides -ethyleniques requis sont synthetises par thiorearrangement de claisen des -hydroxyaminothiocetals de cetene de s-allyle correspondants. Le diastereoisomere syn est obtenu de facon majoritaire (ed 70%). Un modele pseudocyclique chaise explique cette configuration majoritaire. L'hydroboration des -hydroxythioamides -ethyleniques syn est chimioselective et conduit aux thioamides dihydroxyles syn-anti majoritairement. Ces dihydroxythioamides syn-anti sont cyclises en valerolactones de configuration trans. Cette configuration a ete etablie par rmn #1#3c et par effet noe et elle permet d'attribuer une configuration anti au produit obtenu lors de l'hydroboration. Nous proposons un modele sans chelation bore-soufre afin d'expliquer cette selectivite anti. Nous avons enfin ouvert une nouvelle voie de synthese des trans -lactones a partir des -hydroxythioamides -ethyleniques anti.
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35

BERUBEN, DOV. "Carbometallation diastereoselective de vinylmetaux. Application a la synthese de cyclopropanes metalles." Paris 6, 1994. http://www.theses.fr/1994PA066050.

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Au cours de ce travail, nous avons realise la carbometallation d'ethers allyliques metalles en position 3, pour obtenir la formation d'un organogembismetallique-1,1. Dans des conditions experimentales precises, celui-ci peut subir une reaction d'elimination -1,3 pour conduire au cyclopropylmetal correspondant, via un etat de transition en w, avec double inversion de configuration au niveau des centres reactifs. Ce meme protocole a pu etre realise a partir d'ethers homoallyliques secondaires metalles en position 3. Un organogembismetallique-n,n dialkyle est alors mis en evidence pour la premiere fois. Celui-ci peut, dans des conditions analogues, conduire a un cyclopropylmetal tertiaire sous forme d'un seul isomere, presentant une relation syn entre les deux substituants. Cependant, la diastereoselectivite du processus d'elimination-1,3 peut etre modifiee si le methoxymethyl ether est soit benzylique, soit vinylique. Dans ce cas, l'intermediaire bimetalle adopte une conformation relative differente dans laquelle le metal, ne participant pas a l'elimination, se coordine au systeme insature. Cette interaction dipolaire, bien que deja decrite dans la litterature, n'a jamais eu a notre connaissance d'implication sur la stereochimie. Or, elle apparait responsable ici, de la stereochimie du cyclopropane. Toutefois, une interaction sterique-1,2 a de meme ete mise en evidence et semble etre predominante sur le deroulement stereochimique lors de l'elimination-1,3. Il a ete ainsi possible d'etablir un ordre de preseance des differents groupements qui influent sur la stereochimie
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36

REZAEI, HADI. "Carbometallation diastereoselective d'alcynes vrais metalles et rearrangement de fritsch-buttenberg-wiechell." Paris 6, 2000. http://www.theses.fr/2000PA066409.

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Dans le premier chapitre du memoire grace a la reaction de carbometallation des ethers propargyliques nous pouvons acceder a des dienes 1-4 substitues en 3 avec de bons exces diastereoisomeriques. De meme dans le cas des derives de la 1-phenylethylamine ces reactions de carbometallation conduisent a ces dienes avec de bons exces diastereoisomeriques. Ces derniers peuvent alors conduire apres oxydation de l'azote et par reactions successives de cope et retro-cope a des n-oxo pyrolidines precurseurs des pyrolidines. Nous avons vu aussi que la carbometallation des ethers acetyleniques vrais peut conduire aux memes dienes 1-4 substitues en 3 subissant une reaction d'elimination en liberant in situ la copule chirale pour conduire aux 1-4 enynes substitues en 3. Dans le second chapitre de ce memoire nous avons vu que la synthese des carbenoides zinciques vinyliques nous permet d'acceder (pour la premiere fois) a des alcynes disubstitues par des groupements alkyle avec de bons rendements, grace au rearrangement de fritsch-buttenberg-wiechell qui n'etait connu qu'en serie aromatique. Pour ce faire nous avons du mettre au point une nouvelle voie de synthese de 1,1 dihalogeno 2,2 dialkyl ethylenes. De plus, ces carbenoides zinciques permettent un total transfert avec retention de configuration des carbones asymetriques en beta de ces carbenoides. Par contre dans le cas des carbenoides comportant un heteroatome en beta (o, s) ces derniers sont extremement stables (meme aux reflux du thf). Cette grande stabilite a alors ete mise a profit pour les aryler et hydroxyalkyler.
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37

LORTHIOIS, EDWIGE. "Synthese enantioselective et diastereoselective de tetrahydrofurannes. De pyrrolidines et de piperidines." Paris 6, 1997. http://www.theses.fr/1997PA066445.

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Differents enynes polysubstitues ont ete metalles en position propargylique. Apres transmetallation en organozincique, une rapide reaction de cyclisation anionique a lieu pour conduire a des tetrahydrofurannes et a des pyrrolidines de geometrie definie selon un etat de transition de type zinca-ene-allene. La reaction de cyclisation d'enolates de zinc d'esters alpha-amines sur une double liaison non activee permet d'acceder a des pyrrolidines polysubstituees a partir de substrats simples. L'influence de substituants, places sur la chaine lineaire de l'amino-ester, sur la stereochimie de la reaction de cyclisation a ete etudiee. La diastereoselectivite ainsi obtenue peut s'expliquer par un etat de transition de type amino-zinc-enolate. L'introduction d'une copule chirale sur l'atome d'azote permet d'acceder la synthese enantioselective d'anologues beta-methyles de la proline. La reaction de cyclisation d'enolates de zinc d'esters alpha-amines a ete appliquee avec succes a la synthese diastereoselective de piperidines di-, tri-, tetra- et penta-substituees. La reaction de carbolithiation intermoleculaire d'enynes silyles conduit a un organolithien sous deux formes metallotropiques : la forme allenique et la forme propargylique. Une reaction de transmetallation en organozincique conduit au seul isomere allenique, qui reagit selon un processus s#e2' avec differents electrophiles pour donner le derive propargylique correspondant. Cette reaction a ete etendue en version intramoleculaire et permet la formation de cycles a 3, 4, 5 et meme 6 chainons avec des rendements moyens a bons.
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38

Nimkar, Kalpana Sandeep. "Studies in asymmetric synthesis: Diastereoselective manipulations of conformationally anchored heterocycles and carbocycles." Diss., The University of Arizona, 1994. http://hdl.handle.net/10150/186994.

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The research, to be presented in two chapters discusses the development of new methods in asymmetric synthesis which may be applicable to the total synthesis of natural products. Chapter 1. We have developed the methodology to functionalize heterocycles such as tetrahydropyran and tetrahydrofuran using intermolecular diastereoselective radical trapping reactions. This method was also extended to prepare bicyclic acetals with three chiral centers using intramolecular radical reactions. The stereocontrol in both intermolecular and intramolecular reactions was studied. This methodology may be developed further to synthesize deoxygenated and substituted carbohydrates. Chapter 2. The highly functionalized eight membered carbocycle is the basic structural unit of many natural products of biological interest. The methodology developed and presented in this chapter utilizes chiral cyclopropyl ketals of eight member carbocycle and introduces functionalities on the eight membered ring with good stereocontrol. This methodology has direct application in the synthesis of many natural products containing functionalized eight member carbocycles.
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39

Findley, Thomas J. K. "Diastereoselective SMI2-mediated cyclisations in an approach to the skeleton of pleuromutilin." Thesis, University of Manchester, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.498964.

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40

焦關勝 and Guansheng Jiao. "Ketone catalyzed diastereoselective and enantioselective epoxidation of olefins: catalyst design and syntheticapplication." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2000. http://hub.hku.hk/bib/B31240392.

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41

KLEIN, SOPHIE. "Carbolithiation diastereoselective et enantioselective d'olefines heterosubstituees. Etude de la stabilite configurationnelle d'organometalliques." Paris 6, 1995. http://www.theses.fr/1995PA066356.

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La reaction de carbolithiation d'olefines heterosubstituees homoallyliques semble etre assez difficile. Par contre la reaction d'allylzincation de ces olefines peut avoir lieu dans l'ether a la temperature ambiante avec un total controle de la regioselectivite. La reaction de carbolithiation des derives cinnamiques dans des solvants peu polaires est facilitee par l'adjonction de tetramethylethylene diamine. L'organolithien sp#3 benzylique, issu de cette reaction de carbolithiation, s'equilibre rapidement vers l'organolithien thermodynamiquement le plus stable, dans lequel la chelation intramoleculaire entre l'heteroatome et l'atome de lithium fige la conformation de la molecule permettant ainsi l'introduction diastereoselective d'un electrophile avec retention de configuration, le diastereoisomere anti etant alors obtenu. Cet organolithien benzylique, peut etre transmetalle en derive organozincique correspondant en presence de sels de zinc. Cette etape se passe avec une totale inversion de configuration, conduisant ainsi au diastereoisomere syn. De plus cet organozincique est configurationnellement stable a -30c pendant 4 heures. En presence d'une diamine chirale telle que la sparteine (-), cette reaction de carbolithiation devient hautement enantioselective et permet d'obtenir soit l'enantiomere (s) soit l'enantiomere (r) suivant la nature de la stereochimie (e) ou (z) de l'olefine de depart. Il est a noter que dans certains cas la diamine participant a la reaction de carbolithiation peut etre utilisee en quantite catalytique ce qui represente un grand interet en synthese organique
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42

Moss, Thomas. "New Methods in Stereoselective Alkylation : Enantio- and Diastereoselective Ring Opening of Aziridines." Thesis, University of Manchester, 2010. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.516400.

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43

Stewart, Hannah Lindsey. "Synthesis of partially saturated bicyclic heteroaromatics : sp3-enriched scaffolds for drug discovery." Thesis, University of Cambridge, 2019. https://www.repository.cam.ac.uk/handle/1810/287948.

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Recent years have seen an expansion beyond the more druggable biological targets into novel areas of biological space. However, drug discovery campaigns against these challenging targets have been afflicted with low hit rates during screening campaigns and high levels of candidate attrition during clinical trials. Subsequent studies have looked to explore the underlying factors to these challenges and have identified the lack of scaffold diversity and poor physicochemical properties in screening libraries as the leading causes. In an attempt to address this issue drug discovery strategies such as fragment-based drug discovery and lead-oriented synthesis have been developed which control and direct the compound properties within screening libraries towards relevant areas of chemical space. In addition, strategies such as diversity oriented synthesis aim to synthesise structurally complex and diverse compounds, expanding screening collections into previously under-explored areas of chemical space. This thesis reports the development of a step-efficient, modular and highly adaptable synthetic route for the synthesis of partially saturated bicyclic heteroaromatic scffolds (Figure i). The designed route takes advantage of the large chiral pool provided by amino acids, with each scaffold synthesised in just 4-6 steps from these readily available enantiopure starting materials. The mild conditions allow for excellent functional group tolerance, thus enabling the incorporation of growth vectors for chemical elaboration from the outset, a strong advantage in the drug discovery process. Overall, 29 partially saturated bicyclic heteroaromatic compounds were synthesised based around 7 different scaffolds. These demonstrated a number of possible areas for diversifation both on and around the scaffold, including variation of functional groups (Figure i, red), double (cis-diastereoisomers) and single (R2- and R3-positions) substitution patterns, variation of the 5-membered heterocycle (Figure i, green) and increased size of the saturated ring (Figure i, blue). Furthermore, careful selection of the substituents, heterocycle and size of the saturated ring would enable the synthesis of screening libraries within the constraints of fragment-like, lead-like or drug-like structures. The final library has been incorporated into the Diamond XChem high-throughput crystallography program and initial screening has identified a weakly binding hit for Activin A.
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44

Eno, Meredith Suzanne. "Development of Metal-Catalyzed Asymmetric Carbon-Carbon Bond Forming Reactions." Thesis, Boston College, 2017. http://hdl.handle.net/2345/bc-ir:107422.

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Thesis advisor: James P. Morken
This dissertation describes the development of four metal-catalyzed carbon-carbon bond forming methods. The first project presented is a palladium-catalyzed proparyl-allyl cross-coupling which proceeds via a kinetic resolution to give enantioenriched 1,5-enynes. Next the asymmetric rhodium-catalyzed hydroformylation of 1-alkenes is described. This reaction delivers synthetically useful a-chiral aldehydes in up to 98:2 er and up to 15:1 branched to linear ratio. The development of a unique nickelcatalyzed asymmetric Kumada coupling of cyclic sulfates is presented. Mechanistic studies reveal the reaction proceeds via an SN2 oxidative addition of a chiral nickelcomplex. Finally, a-Substituted allyl bis(boronic) esters, which are derived from 1,2-diboration of 1,3-dienes are shown to undergo allylation and subsequent Suzuki coupling with aldehydes tethered to sp2 electrophiles. The carbocycle products obtained bear three contiguous stereocenters and were used as intermediates in the synthesis of complex molecules
Thesis (PhD) — Boston College, 2017
Submitted to: Boston College. Graduate School of Arts and Sciences
Discipline: Chemistry
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45

Reid, Gary Patrick. "Diastereoselective conjugate additions of Grignard reagents to homochiral fumarates derived from Oppolzer's sultam." Thesis, University of Glasgow, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.400696.

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46

Jiao, Guansheng. "Ketone catalyzed diastereoselective and enantioselective epoxidation of olefins : catalyst design and synthetic application /." Hong Kong : University of Hong Kong, 2000. http://sunzi.lib.hku.hk/hkuto/record.jsp?B21981772.

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47

O'Meara, Jeffrey A. "Dynamic kinetic resolution: Diastereoselective amination of alpha-halo esters and alpha-halo imidazolidinones." Thesis, University of Ottawa (Canada), 1995. http://hdl.handle.net/10393/9493.

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The synthesis of optically active N-protected $\alpha$-amino esters and $\alpha$-amino imidazolidinones via a dynamic kinetic resolution protocol will be discussed. The methodology is based on fundamental reactivity differences between diastereomeric $\alpha$-halo esters and $\alpha$-halo imidazolidinones. The process involves nucleophillic displacement of the diastereomeric $\alpha$-halogenated esters and imidazolidinones with benzylamine. The corresponding displacement products are obtained with 70 - $>$ 98% de. Both absolute configurations are possible at the aminated postion by appropriate choice of the chiral auxiliary. The application of this methodology towards the synthesis of several optically active $\alpha$-amino esters was investigated. A five step sequence, starting from commercially available acid chlorides, was developed for synthesizing $\alpha$-amino esters in $\sim$40% overall yield. By utilizing dibenzylamine as the nucleophile, the DKR process has been effectively utilized in an approach to Reetz aldehydes ($\alpha$-dibenzylamino aldehydes). The increased bulk of dibenzylamine provides increased diastereoselectivity relative to benzylamine and the Reetz aldehyde precursors are obtained with a high degree of optical purity. Mechanistic aspects the reaction will also be discussed.
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48

Fryling, James Allen. "Enantiomerically pure acetals in organic synthesis: Resolutions and diastereoselective alkylations of alpha-hydroxy esters." Diss., The University of Arizona, 1990. http://hdl.handle.net/10150/185332.

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The diastereomeric tetrahydropyranyl (THP) and tetrahydrofuranyl (THF) ethers of a variety of α-hydroxyesters were synthesized and separated by column chromatography. The separability of the diastereomers was found to be a general phenomenon which allowed for wide variations in both the THP/THF ring and the α-hydroxyester. The resolved compounds could be deprotonated and alkylated diastereoselectively with a variety of electrophiles. The diastereoselectivity ranged from 1:1 to 12:1 depending on the α-hydroxyester, the alkylating agent, and the reaction conditions. In most cases the diastereomeric products of the alkylation were also separated by column chromatography. This alkylation method was used in the synthesis of the natural product (S)-frontalin and its enantiomer with optical purity. Modifications to the THP and THF rings were synthesized in an attempt to develop a "chiral THP". The (S)-methyl lactyl, (S)-methyl mandelyl, and (R)-pantolactyl 3-benzyloxytetrahydrofuranosides were synthesized and separated. Transacetalization to the methyl furanosides gave "chiral THF's" which were used in the resolution of other racemic α-hydroxyesters.
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49

Evans, A. C. "Diastereoselective desymmetrisation of cyclic meso-anhydrides and derivatisation for use in natural product synthesis." Thesis, University of Cambridge, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.598878.

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This thesis describes the development of a new method to desymmetrise meso-succinic and glutaric anhydrides and its application in the synthesis of a fragment of the biologically active natural product rapamycin. It is divided into four chapters: - Chapter one provides an introduction to the concept of desymmetrisation, followed by a literature summary reviewing the history of anhydride desymmetrisation methodology over the past fifty years and application in natural product synthesis. - Chapter two describes the project background more specifically and the original project aims are delineated. - Chapter three presents the results and discussion: proof of concept is followed by application of the method to generate both acid-amide and ester-amide derivatives. Optimisation studies, scope of reaction and theoretical modelling studies are all incorporated within this section. A general background on the natural product rapamycin is then given, and use of the novel desymmetrisation methodology in the synthesis of a fragment of the interesting and challenging natural product is discussed. - Chapter four concludes the thesis and makes some suggestions for future work. - Chapter five provides a formal account of the experimental procedures. References and appendices containing supporting X-ray crystal structure data follow.
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50

Hendea, Daniela. "Diastereoselective alkylation of bi- and tricyclic lactimethers as a pathway to biologically relevant diketopiperazines." [S.l. : s.n.], 2007. http://nbn-resolving.de/urn:nbn:de:bsz:93-opus-31845.

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