Barbara Weiner

Bio: Barbara Weiner is an academic researcher from University of Groningen. The author has contributed to research in topics: Enantioselective synthesis & Amino acid. The author has an hindex of 6, co-authored 13 publications receiving 673 citations.

Recent advances in the catalytic asymmetric synthesis of β-amino acids

Abstract: In this critical review, the progress in catalytic asymmetric synthesis of β-amino acids is discussed, covering the literature since 2002. The review treats transition metal catalysis, organocatalysis and biocatalysis and covers the most important synthetic methods, such as hydrogenation, the Mannich reaction and conjugate additions (160 references).

Aldehyde Selective Wacker Oxidations of Phthalimide Protected Allylic Amines: A New Catalytic Route to beta(3)-Amino Acids

Abstract: A new method for the synthesis of beta(3)-amino acids is presented. Phthalimide protected allylic amines are oxidized under Wacker conditions selectively to aldehydes using PdCl(2) and CuCl or Pd(MeCN)(2)Cl(NO(2)) and CuCl(2) as complementary catalyst systems. The aldehydes are produced in excellent yields and exhibit a large substrate scope. Beta-amino acids and alcohols are synthesized by oxidation or reduction and subsequent deprotection.

Phenylalanine Aminomutase-Catalyzed Addition of Ammonia to Substituted Cinnamic Acids: a Route to Enantiopure alpha- and beta-Amino Acids

Abstract: An approach is described for the synthesis of aromatic α- and β-amino acids that uses phenylalanine aminomutase to catalyze a highly enantioselective addition of ammonia to substituted cinnamic acids. The reaction has a broad scope and yields substituted α- and β-phenylalanines with excellent enantiomeric excess. The regioselectivity of the conversion is determined by substituents present at the aromatic ring. A box model for the enzyme active site is proposed, derived from the influence of the hydrophobicity of substituents on the enzyme affinity toward various substrates.

Biocatalytic Enantioselective Synthesis of N-Substituted Aspartic Acids by Aspartate Ammonia Lyase

Abstract: The gene encoding aspartate ammonia lyase (aspB) from Bacillus sp. YM55-1 has been cloned and overexpressed, and the recombinant enzyme containing a C-terminal His(6) tag has been purified to homogeneity and subjected to kinetic characterization. Kinetic studies have shown that the His(6) tag does not affect AspB activity. The enzyme processes L-aspartic acid, but not D-aspartic acid, with a K(m) of approximately 15 mM and a k(cat) of approximately 40 s(-1). By using this recombinant enzyme in the reverse reaction, a set of four N-substituted aspartic acids were prepared by the Michael addition of hydroxylamine, hydrazine, methoxylamine, and methylamine to fumarate. Both hydroxylamine and hydrazine were found to be excellent substrates for AspB. The k(cat) values are comparable to those observed for the AspB-catalyzed addition of ammonia to fumarate ( approximately 90 s(-1)), whereas the K(m) values are only slightly higher. The products of the enzyme-catalyzed addition of hydrazine, methoxylamine, and methylamine to fumarate were isolated and characterized by NMR spectroscopy and HPLC analysis, which revealed that AspB catalyzes all the additions with excellent enantioselectivity (>97 % ee). Its broad nucleophile specificity and high catalytic activity make AspB an attractive enzyme for the enantioselective synthesis of N-substituted aspartic acids, which are interesting building blocks for peptide and pharmaceutical synthesis as well as for peptidomimetics.

Copper-Catalyzed Conjugate Addition of a Bis(triorganosilyl) Zinc and a Methyl(triorganosilyl) Magnesium

Abstract: A practical copper-catalyzed conjugate silylation of α,β-unsaturated carbonyl compounds 4 utilizing bis(triorganosilyl) zinc reagent 3 is described. Moreover, mixed methyl(triorganosilyl) magnesium 7 also transfers its silyl ligand to simple enones 4 under copper catalysis.

Recent advances in the catalytic asymmetric synthesis of β-amino acids

Abstract: In this critical review, the progress in catalytic asymmetric synthesis of β-amino acids is discussed, covering the literature since 2002. The review treats transition metal catalysis, organocatalysis and biocatalysis and covers the most important synthetic methods, such as hydrogenation, the Mannich reaction and conjugate additions (160 references).

Catalytic Selective Synthesis

Abstract: Complete control of the product of a catalytic reaction can be achieved on the basis of catalyst structure, even when the reaction conditions are nearly identical. Catalyst-controlled selectivity is well established for enantioselective catalysis but less formulated for catalytic regio-, chemo-, or product-selective reactions. This Review describes selective transformations of the same starting materials into two or more different products simply by the choice of catalyst. By collecting and highlighting examples of selective catalysis, we hope that the field will be encouraged by the progress that has been made while bringing attention to unmet needs in the design and mechanistic understanding of selective catalysts.

Rhodium-catalysed asymmetric hydrogenation as a valuable synthetic tool for the preparation of chiral drugs

Abstract: During the last few decades, rhodium-catalysed asymmetric hydrogenation of diverse alkene classes has emerged as a powerful synthetic tool in the pharmaceutical industry, contributing to the manufacturing of chiral drugs, recent drug candidates for clinical trials, and major synthetic precursors of drugs. Numerous efficient chiral rhodium complexes, most of which are derived from enantiopure phosphorus ligands, have been employed for the preparation of chiral drugs and intermediates thereof. This review article is intended to provide an updated overview of the most striking contributions in this field, organised according to substrate class: acrylate derivatives, itaconate derivatives, α-substituted enamides, α-arylenol acetates, and minimally functionalised olefins.