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Université de Neuchâtel

Catalytic Hydrogenation of meso-Octamethylporphyrinogen (Calix[4]pyrrole)

Journot, Guillaume ; Letondor, Christophe ; Neier, Reinhard ; Stoeckli-Evans, Helen ; Savoia, Diego ; Gualandi, Andrea

In: Chemistry - A European Journal, 2010, vol. 16, no. 4, p. 4224-4230

Hydrogenation of meso-octamethylporphyrinogen (calix[4]pyrrole) with a number of heterogeneous catalysts under different experimental conditions has been investigated. GC-MS analyses of the reaction mixtures showed the formation of one to four products in low to moderate yields: three of them were diastereoisomers of the product derived from half-hydrogenation of the substrate, and displayed...

Université de Neuchâtel

5-Hydroxyalkyl derivatives of tert-butyl 2-oxo-2,5-dihydro-1H-pyrrole-1-carboxylate: diastereoselectivity of the Mukaiyama crossed-aldol-type reaction

Vallat, Oliver ; Buciumas, Ana-Maria ; Neier, Reinhard ; Stoeckli-Evans, Helen

In: Acta Crystallographica Section C : Crystal Structure Communications, 2009, vol. C65, no. 4, p. o171-o175

The title compounds, rac-(1'R,2R)-tert-butyl 2-(1'-hydroxyethyl)-3-(2-nitrophenyl)-5-oxo-2,5-dihydro-1H-pyrrole-1-carboxylate, C17H20N2O6, (I), rac-(1'S,2R)- tert-butyl 2-[1'-hydroxy-3'-(methoxycarbonyl)propyl]-3-(2-nitrophenyl)-5-oxo-2,5-dihydro-1H-pyrrole-1-carboxylate,...

Université de Neuchâtel

4,4-Bis(1H-pyrrol-2-yl)pentanol

Journot, Guillaume ; Neier, Reinhard ; Stoeckli-Evans, Helen

In: Acta Crystallographica Section E : Structure Reports Online, 2010, vol. E66, no. 2, p. o393, sup1-8

The title achiral compound, C13H18N2O, crystallized in the chiral monoclinic space group P21. The pyrrole rings are inclined to one another by 62.30 (11)°, and the propanol chain is in an extended conformation. In the crystal, the two pyrrole NH groups are involved in intermolecular N-H ··· O hydrogen bonds, leading to the formation of a...

Université de Neuchâtel

Influence of the nature and substitution of chiral 2,3-epoxy alcohol derivatives on the enantiomeric elution order on chiralcel OD column

Nacro, Kassoum ; Zedde, Chantal ; Escudier, Jean-Marc ; Baltas, Michel ; Gorrichon, Liliane ; Neier, Reinhard

In: Chirality, 1998, vol. 10, no. 9, p. 804-807

A number of 2,3-epoxy alcohol derivatives (1-16), obtained either as racemates or through the Sharpless asymmetric epoxidation reaction, were studied on a Chiralcel OD column. Nearly all compounds exhibit good enantioselective resolution on this chiral support. The order of elution of enantiomers is reversed between nerol and geraniol compounds. For 2,3-epoxy alcohols bearing a remote alkoxy (or...

Université de Neuchâtel

Synthesis of Bisubstrate Inhibitors of Porphobilinogen Synthase from Pseudomonas aeruginosa

Gacond, Sabine ; Frère, Frederic ; Nentwich, Merle ; Faurite, Jean-Philippe ; Frankenberg-Dinkel, Nicole ; Neier, Reinhard

In: Chemistry & Biodiversity, 2007, vol. 4, no. 2, p. 189-202

Porphobilinogen synthase (PBGS) synthesizes porphobilinogen 2 (PBG), the common precursor of all natural tetrapyrroles, through an asymmetric condensation of two molecules of 5-aminolevulinic acid 1 (ALA). Symmetrically linked dimers 7-11 derived from levulinic acid 3 (γ-oxovaleric acid) have been synthesized to mimic the assumed bisubstrate bound to the active site of...

Université de Neuchâtel

Malonylation/Decarbalkoxylation of Furan Derivatives as Key Steps for the Preparation of Nonactic Acid Derivatives. Part I [1]

Simone, Jean-Mary ; Loiseau, François ; Carcache, David ; Bobal, Pavel ; Jeanneret-Gris, Julie ; Neier, Reinhard

In: Monatshefte für Chemie / Chemical Monthly, 2007, vol. 138, no. 2, p. 131-139

A malonylation/decarbalkoxylation sequence from 2-substituted furans was investigated in view of developing a scalable synthesis of hydrophobic nonactic acid analogues.

Université de Neuchâtel

Radical Couplings as Key Steps for the Preparation of Derivatives of Nonactic Acid

Loiseau, François ; Simone, Jean-Mary ; Carcache, David ; Bobal, Pavel ; Neier, Reinhard

In: Monatshefte für Chemie / Chemical Monthly, 2007, vol. 138, no. 2, p. 121-129

Free radical couplings from furan, as cheap starting material, were studied in view of developing a rapid strategy en route to the synthesis of derivatives of nonactin. The chain containing the alcohol function was introduced in one or two steps in 86% yield. For the introduction of the second chain with the ester function two different coupling methods were tested. Starting from the...

Université de Neuchâtel

Rac-(2R*,3R*)-S-Ethyl-4-Chloro-3-Hydroxy-2-Phenylbuthanethioate and Rac-(2R*,3R*)-S-Ethyl-2-Phenyl-3-(tosyloxy)buthanethioate: Dichotomy of the Stereoselectivity of the Mukaiyama Reaction

Vallat, Oliver ; Buciumas, Ana-Maria ; Neier, Reinhard ; Stoeckli-Evans, Helen

In: Journal of Chemical Crystallography, 2009, vol. 40, no. 1, p. 10-14

The title compounds, rac-(2R*,3R*)-S-ethyl-4-chloro-3-hydroxy-2-phenylbuthanethioate (I) and rac-(2R*,3R*)-S-ethyl-2-phenyl-3-(tosyloxy)buthanethioate (III), are both composed of a S-ethyl 2-phenylbutanethioate moiety but have different geometries. Compound I is substituted in the 3 and 4 positions by a hydroxyl group and a chlorine atom, respectively. In compound III...

Université de Neuchâtel

The High Stereoselectivity of the Tandem Sequence Diels-Alder Reaction/Ireland­-Claisen Rearrangement Starting from Substituted O-(E)-Buta-1,3-dienyl Ketene Acetals and Cyclic Dienophiles

Soldermann, Nicolas ; Velker, Jörg ; Neels, Antonia ; Stoeckli-Evans, Helen ; Neier, Reinhard

In: Synthesis, 2007, vol. 15, p. 2379-2387

A new tandem reaction leads to bicyclic cyclohexene derivatives with complete control of the relative configuration of the four chiral centers formed. The high diastereoselectivity is the consequence of an endo-selective Diels-Alder reaction followed by an Ireland-Claisen rearrangement that proceeds via a boat-like transition state.

Université de Neuchâtel

Evaluation of dipeptide-derivatives of 5-aminolevulinic acid as precursors for photosensitizers in photodynamic therapy

Berger, Yann ; Ingrassia, Laurent ; Neier, Reinhard ; Juillerat-Jeanneret, Lucienne

In: Bioorganic & Medicinal Chemistry, 2003, vol. 11, no. 7, p. 1343-1351

N-terminal-blocked and N-terminal-free pseudotripeptide Gly-Gly and Gly-Pro derivatives of 5-aminolevulinic acid (ALA) esters were synthesized as potential specific substrates for cellular peptidases and precursors for the production of the photosensitizer protoporphyrin IX (PpIX). These precursors were evaluated using human cell lines of either carcinoma or endothelial origin. N-blocked or...