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S Bräse

Publications and source records attributed to S Bräse.

8 recordsLinked to original sources
PubMed2003

Natural product-like and other biologically active heterocyclic libraries using solid-phase techniques in the post-genomic era.

High-throughput technologies allow the selection of new biological targets for drug discovery in the post-genomic era. These tools increase the need of new methods to rapidly obtain potent small molecules and natural products to discover new lead structures. In particular, the solid-phase synthesis offers a great potential to obtain large compound sets.

Combinatorial Chemistry Techniques↗
PubMed2001

[2,2]paracyclophane-based N,O-ligands in alkenylzinc additions to aldehydes.

[reaction: see text] The application of planar and central chiral [2,2]paracyclophane-based N,O-ligands in asymmetric alkenylzinc additions to various aldehydes is described, which gives rise to very high ee's especially for difficult substrates. A fine-tuning of the alkenylzinc species by employing different transmetalation reagents is reported, allowing control of the steric bulk of the alkenylzinc species and thus the selectivity of the catalysis.

Journal Article↗
PubMed2001

A Novel Hydrazine Linker Resin and Its Application for the Solid-Phase Synthesis of alpha-Branched Primary Amines.

A novel hydrazine linker resin for solid-phase organic synthesis has been developed. Starting from Merrifield resin, the new N-butyl-N-methylpolystyrene-hydrazine linker is prepared in three steps. Polymer-supported hydrazones, readily prepared from aldehydes and the hydrazine resin, react with alkyl- and arylorganolithium reagents under 1,2-addition to the C-N double bond to afford the corresponding hydrazines. Release from solid support was achieved by reductive N-N bond cleavage using the borane-tetrahydrofuran complex. The resulting alpha-branched primary amines were protected as their amides or carbamates, respectively, and, after purification, were obtained in good overall yields and in high purity (12 examples).

Journal Article↗
PubMed2000

A novel solid-phase synthesis of highly diverse guanidines: reactions of primary amines attached to the T2 linker.

The reaction of primary amines with the T2 diazonium resin generates polymer-bound triazenes, which can in turn be acylated by the addition of isothiocyanate. The formed thioureas are readily transformed into the corresponding guanidines by the reaction with amines in the presence of mercury(II) oxide, tosyl chloride, or silver nitrate. This reaction sequence furnishes trisubstituted guanidines that are potentially useful pharmacophores.

Amines↗
PubMed2000

The First Stable Diazonium Ion on Solid Support-Investigations on Stability and Usage as Linker and Scavenger in Solid-Phase Organic Synthesis Nitrogen-Based Linkers, Part 8. This work was supported by the Fonds der Chemischen Industrie (Liebig-Stipend to S.B.) and the Deutsche Forschungsgemeinschaft (BR1750-1). We thank Prof. Dr. D. Enders for the generous support of our work. The companies BASF AG, Bayer AG, Degussa-Hüls AG, and Calbiochem-Novabiochem AG are acknowledged for donations of chemicals and Grünenthal GmbH for financial support. For DSC measurements we also thank Prof. Dr. Franz-Josef Wortmann and Dr. Numan Özgün at the Deutsches Wollforschungsinstitut (DWI) at the RWTH Aachen. Part 7: M. Lormann, S. Dahmen, S. Bräse, Tetrahedron Lett. 2000, 41, 3813-3816.

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Journal Article↗
PubMed1999

Chemistry, Biology, and Medicine of the Glycopeptide Antibiotics.

The war against infectious bacteria is not over! Although vancomycin and glycopeptide antibiotics have provided a strong last line of defence against many drug-resistant bacteria, their overuse has given rise to more dangerous strains of bacteria. An understanding of the chemistry and biology of these highly complex glycopeptides are destined to play a crucial role in the discovery of new antibiotics.

Journal Article↗
PubMedDate not supplied

Solid-phase synthesis of urea and amide libraries using the T2 triazene linker.

Starting from Merrifield resin, primary amines were immobilized in two steps by triazene linkage (T2-linker). While reaction with isocyanates gave rise to resin-bound urea derivatives, acylation by acid chlorides or anhydrides furnished amides bound to solid support via the nitrogen atom, therefore representing a novel backbone amide linker. Cleavage from the resin was conducted using dilute trimethylsilyl chloride or trifluoroacetic acid, respectively, to yield ureas and amines/amides in a library format (altogether 60 examples; manual synthesis: 17 ureas, 6 mono-alkylated ureas [including dihydroxylation and ozonolysis/Wittig reaction]; automated synthesis: 15 ureas, 15 amides) in high purities and good overall yields. The synthesis of a small library (4 x 4 member) was successfully conducted on a Bohdan Neptune synthesizer.

Journal Article↗