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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...

Université de Neuchâtel

On the formation of the mixed pyrrole catalysed by porphobilinogen synthase from Rhodobacter spheroides

Lüönd, Rainer Martin ; Neier, Reinhard

In: Biochimica et Biophysica Acta (BBA), 1996, vol. 1289, no. 1, p. 83-86

The enzyme porphobilinogen synthase (PBGS) catalyses the formation of porphobilinogen (PBG) from two molecules of 5-aminolevulinic acid (ALA). It has been claimed that the PBGS from Rhodobacter spheroides is able to form a mixed pyrrole, from one molecule of 5-aminolevulinic acid and one molecule of levulinic acid. The chemical synthesis of this mixed pyrrole allowed to show, that the...

Université de Neuchâtel

The X-ray structure of yeast 5-aminolaevulinic acid dehydratase complexed with two diacid inhibitors

Erskine, P. T. ; Coates, L. ; Newbold, R. ; Brindley, A. A. ; Stauffer, Frédéric ; Wood, S. P. ; Warren, M. J. ; Cooper, J. B. ; Shoolingin-Jordan, P. M. ; Neier, Reinhard

In: FEBS Letters, 2001, vol. 503, no. 2-3, p. 196-200

The structures of 5-aminolaevulinic acid dehydratase complexed with two irreversible inhibitors (4-oxosebacic acid and 4,7-dioxosebacic acid) have been solved at high resolution. Both inhibitors bind by forming a Schiff base link with Lys 263 at the active site. Previous inhibitor binding studies have defined the interactions made by only one of the two substrate moieties (P-side substrate) which...

Université de Neuchâtel

The photochemical[2 + 2]cycloaddition to N-methoxycarbonyl-5,6-dihydro-4-pyridone

Guerry, Philippe ; Neier, Reinhard

In: Journal of the Chemical Society, Chemical Communications, 1989, vol. 22, p. 1727 - 1728

The N-methoxycarbonyl-5,6-dihydro-4-pyridone (1) undergoes photochemical [2 + 2] cycloaddition with a series of differently substituted alkenes in high yield and with extremely high regioselectivity.

Université de Neuchâtel

Lewis-acid catalysed tandem reaction Diels–Alder–[3,3] sigmatropic shift between buta-1,3-dienyl thiocyanic acid ester and acryloyl chloride: application in the synthesis of 2-azabicyclo[2.2.2]oct-5-ene derivatives

Schoepfer, Joseph ; Marquis, Christian ; Pasquier, Cécile ; Neier, Reinhard

In: Journal of the Chemical Society, Chemical Communications, 1994, vol. 8, p. 1001-1002

Buta-1,3-dienyl thiocyanic acid ester reacts with acryloyl chloride in presence of Lewis acid catalysts to produce directly the rearranged product of type 3bvia a combination of a Diels-Alder reaction with a [3,3] sigmatropic shift; the 1,4-substituted cyclohexene is easily transformed into the 2-azabicyclo[2.2.2]oct-5-ene derivative 6b, which has been used as precursor for...

Université de Neuchâtel

Synthesis of (E)- and (Z)-1-Thiocyanatobuta-1,3-dienes and their Diels-Alder Reaction

Huber, Stefan ; Stamouli, Peristera ; Neier, Reinhard

In: Journal of the Chemical Society, Chemical Communications, 1985, vol. 9, p. 533-534

1-Thiocyanatobuta-1,3-dienes react with strong dienophiles to produce directly the rearranged products of type (6) via a combination of a Diels-Alder reaction with a [3,3] sigmatropic shift.

Université de Neuchâtel

The Synthesis of a Pyrazol Analogon of Porphobilinogen with the Help of the Mukaiyama Aldol Reaction

Chaperon, André ; Bertschy, Hugo ; Franz-Schrumpf, Anne-Laurence ; Hugelet, Bertrand ; Neels, Antonia ; Stoeckli-Evans, Helen ; Neier, Reinhard

In: Chimia, 2003, vol. 57, p. 601-606

The synthesis of a pyrazol analogon of porphobilinogen is described. The Mukaiyama crossed aldol reaction is the key step of our approach. The retrosynthetic analysis follows the mechanism for the biosynthesis of porphobilinogen initially proposed by Shemin.

Université de Neuchâtel

Porphobilinogen Synthase : A Challenge for the Chemist ?

Stauffer, Frederic ; Zizzari, Eleonora ; Soldermann-Pissot, Carole ; Faurite, Jean-Philippe ; Neier, Reinhard

In: Chimia, 2001, vol. 55, p. 314-319

The initial steps in the biosynthesis of the tetrapyrrolic dyes, called the 'pigments of life', are highly convergent. The formation of porphobilinogen, the pyrrolic precursor of the tetrapyrrolic skeleton, uses δ-aminolevulinate as the starting material. This amino acid is dedicated to the biosynthesis of tetrapyrroles. However, the chemical condensation of δ-aminolevulinate leads to a...

Université de Neuchâtel

An Unexpected Tandem Reaction between N-Butadienyl-N-alkylketeneN,0-Trimethylsilylacetals of Propionamide and Activated Dienophiles like N-Phenylmaleimide or Acryloyl Chloride

Baak, Marcel ; Rubin, Yves ; Franz, Andreas ; Stoeckli-Evans, Helen ; Bigler, Laurant ; Nachbauer, Jürgen ; Neier, Reinhard

In: Chimia, 1993, vol. 47, p. 233-240

Starting from the N-butadienyl-N-alkylpropionamides 1a-1c the corresponding N,0-trimethylsilylacetals could be obtained using the mixture ofLDA and trimethylsilyl chloride in THF. The unexpected reaction sequence Diels-Alder reaction/acylation between the N-butadienyl-N-alkylketene N,0-trimethylsilylacetal ofpropionamide (2a-2b) and...