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Université de Neuchâtel

Synthese neuer Ringerweiterter Porphyrine als Vorläufer Hexagonal Diskotischer Mesophasen

Herzog, Beat Andreas ; Neier, Reinhard (Dir.)

Thèse de doctorat : Université de Neuchâtel, 2008 ; Th. 2057.

Tetrapyrroles are of fundamental importance such as for the existence of life on our planet. Mentioned for the whole class of these chromophores the examples of chlorophylls for the photosynthesis or of the heme for the cellular respiration are always present. Nature optimized such systems over million of years and made adjustments for the different applications. Natural tetrapyrroles play an...

Université de Neuchâtel

The use of the crossed aldol mukaiyama reaction for the preparation of advanced intermediates for the synthesis of rhazinilam analogues

Buciumas, Ana-Maria ; Neier, Reinhard (Dir.)

Thèse de doctorat : Université de Neuchâtel, 2008 ; Th.2012.

Having studied the previous total syntheses of rhazinilam and of its analogues, we developed our own strategy based the crossed aldol Mukaiyama reaction as the key step. The determination of the diastereoselectivity of the reactions reported above could be achieved with the help X-ray structures. Working with model molecules, by acylation of 1H-pyrrole-2(5H)-one to nitrogen, cleavage of hydroxyl...

Université de Neuchâtel

1,3-Dipolar cycloadditions : click chemistry for a new synthesis of 5-substituted tetrazoles and applications in organocatalysis

Aureggi, Valentina ; Neier, Reinhard (Dir.) ; Sedelmeier, Gottfried (Codir.)

Thèse de doctorat : Université de Neuchâtel, 2007 ; Th.1959.

Tetrazoles are a class of heterocycles with a wide range of applications in medicinal chemistry and in material sciences 1. However a versatile method to synthesize tetrazoles through safe protocols is still highly desirable. Indeed each of the general known procedures uses either toxic metals, expensive reagents, harsh reaction conditions and may lead to the formation of dangerous hydrazoic acid...

Université de Neuchâtel

Synthèse de dérivés de l'acide nonactique : études de méthodes pour introduire diastéréosélectivement des chaînes hydrophobes sur la nonactine

Loiseau, François ; Neier, Reinhard (Dir.)

Thèse de doctorat : Université de Neuchâtel, 2006 ; 1905.

The antibiotic nonactin is used in ammonium ion selective electrodes. Our goal is to develop methods to introduce hydrophobic side chains on nonactin, in order to increase its life time in the semi permeable membrane of a sensor. Simple nonactic acid derivatives such as 275, and a dimer, were synthesized from cheap starting materials. In order to study the possibility of modifying nonactin,...

Université de Neuchâtel

Etude du mécanisme de la porphobilinogène synthase de Pseudomonas aeruginosa : synthèses, études cinétiques et structures déterminées à l’aide des rayons X d’analogues de bisubstrats

Gacond, Sabine ; Neier, Reinhard (Dir.)

Thèse de doctorat : Université de Neuchâtel, 2005 ; 1836.

Ce travail est basé sur l'obtention d'informations sur le mécanisme adopté par l'enzyme porphobilinogène synthase (PBGS, EC 4.2.1.24). La porphobilinogène synthase est impliquée dans la biosynthèse des produits tétrapyrroliques naturels tel que la chlorophylle, l'hème, la vitamine B12, etc. Ces pigments tétrapyrroliques jouent un rôle important dans des processus fondamentaux de la vie...

Université de Neuchâtel

Etude et développement du processus tandem réaction de Diels-Alder/réarrangement de Ireland-Claisen : application à la synthèse de la juvabione

Soldermann, Nicolas ; Neier, Reinhard (Dir.)

Thèse de doctorat : Université de Neuchâtel : 2002 ; 1626.

The length of a synthesis is determinated by the increase of complexity achieved per synthetic operation. Combining several transformations into a one-pot reaction has proven to be an excellent strategy to increase the efficiency of organic synthesis [2]. In our group, we work on the development of new tandem reactions with the sequence Diels-Alder cycloaddition / [3,3] sigmatropic rearrangement....

Université de Neuchâtel

Synthèse d'un précurseur stable du porphobilinogène : un accès rapide et pratique au produit naturel

Soldermann-Pissot, Carole ; Neier, Reinhard (Dir.)

Thèse de doctorat : Université de Neuchâtel : 2002 ; 1625.

A biomimetic synthesis of Porphobilinogen (PBG), the pyrrolic precursor of the tetrapyrrolic skeleton of all 'pigments of life' was developed in our group. The concept was based on the enzymatic mechanism of the condensation of two molecules of d-amino levulinic acid (16) in PBG (9) by PBGS, postulated by Shemin in 1968 [2]. A protected form of PBG could be synthesized [3]. However, the...

Université de Neuchâtel

Porphobilinogène synthase (PBGS) d'Escherichia coli : études cinétiques et rayons X , deux outils permettant la caractérisation du site actif et la détermination du mécanisme enzymatique

Homberger-Zizzari, Eleonora ; Neier, Reinhard (Dir.)

Thèse de doctorat : Université de Neuchâtel : 2002 ; 1637.

The aim of this PhD thesis was to acquire new informations allowing the determination of the mechanism for the transformation of two d-aminolevulinic acid molecules (1) into porphobilinogen (2). This reaction is catalysed by the enzyme porphobilinogen synthase (PBGS, EC 4.2.1.24), which is the second dedicated enzyme in the biosynthesis of tetrapyrrolic compounds such as heme, chlorophyll, etc....

Université de Neuchâtel

Synthèse de dérivés de l'acide d-aminolévulinique, capable de cibler des cellules spécifiques, en vue de leur utilisation en thérapie photodynamique

Berger, Yann ; Neier, Reinhard (Dir.)

Thèse de doctorat : Université de Neuchâtel : 2002 ; 1665.

When 5-aminolevulinic acid (ALA) is administered topically, intravenously or intraperitoneally to tumor-bearing animals or humans, tumour selective production of protoporphyrin IX (PpIX) is frequently observed. Several biophysical, biochemical and physiological factors explain this tumour selectivity, among which the most important ones seem to be: ·A relatively high concentration of the...

Université de Neuchâtel

Développement de méthodes pour la synthèse d’un analogue du Rhazinilame

Vallat, Olivier ; Neier, Reinhard (Dir.)

Thèse de doctorat : Université de Neuchâtel : 2004 ; 1742.

A new synthetic pathway of analogue of rhazinilam, a natural product having antimitotic properties, has been performed. We developed a convergent synthesis around pyrrole ring in application to pyrrole synthesis in two steps perfected in our group. The first key step, the formation of carbon-carbon bond using a Mukaiyama crossed aldol reaction, has been finalized. We made the reaction between the...