Oxidative decarboxylation of α-amino acids with coenzyme PQQ

Oxidative decarboxylation of α-phenylglycine with coenzyme pqq was performed catalytically in the presence of CTAB under mild conditions to give benzaldehyde and benzoic acid.     

Oxidative Rearrangement via Oxycerication with Ce(IV) Salt

α-Arylpropanoic acids are pharmaceutically interesting compounds, some of them exhibit anti-flammatory and analgestic activities1. Even the enormous progress made in the synthesis of α-arylpropanoic acids by 1,2-aryl rearrangement of arylpropanone using thalium (III) nitrate1,2, silver (I) compounds,3,4 lead (IV) acetate5,6 and iodinate7 during the last decades. The route is, however, unsuitable for the preparation of pharmaceutical products (Naproxen, Ibuprofen and so on) because of the …     

Ternary mixed-ligand complexes of copper(II) with α-aminoalkylphosphonic acids and amino acids

Formation of ternary mixed-ligand complexes of copper (II) with 16 -amino acids and -aminophosphonic acids (APA) with a 111 ratio of initial concentrations has been studied by potentiometric titration at 25C and 0.1 M KC1 in aqueous solution. The complexes Cu_pA_nB_sH_q are formed in solution, where A and B are the deprotonated ligands. The stability of the mixed-ligand complexes (log ) increases and the equilibrium is displaced more towards their formation (log K) as the hydrophobic nature of the ligands increases.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 3, pp. 570–575, March, 1991.     

Oxidative cleavage of α, β-unsaturated compounds by pentachlorohydroxoplatinate(IV) in alkaline medium

The kinetics of oxidation of α,β-unsaturated compounds by platinum(IV) in the presence of alkali {[OH⁻]= (1–9) × 10⁻³ mol dm⁻³} have been investigated over the 303–318 K temperature range . The rate of the reaction is dependent on the first power of the concentrations of substrates, oxidant, and alkali. The rate constant increases with an increase in ionic strength and also with increasing dielectric constant of the medium. The oxidation rates follow the order: –CN > –CONH₂ > –COO⁻. The values of the third order rate constant (k₃) for the oxidation of acrylonitrile, acrylamide and acrylate are 1.24, 0.826 and 0.628 mol⁻² dm⁶ s⁻¹ respectively, at 303 K. The oxidations of the substrates by PtCl₅(OH)²⁻ take place by an inner-sphere mechanism. Platinum(IV) is reduced to platinum(II) by the substrates in a one-step two-electron transfer process to give reaction products. The major reaction product, HCHO, is identified from the reaction mixture using i.r. spectrometry, n.m.r. and C, H, N analysis. A tentative reaction mechanism, leading to the formation of products, has been suggested. The activation parameters of the reaction have been evaluated.     

Complexes of copper(II) with sugar α-amino acids as ligands

Summary Complexes of Cu^II with 2-(benzylamino)-2-deoxy-d-glycero-d-talo heptonic acid (BnMa) and 2-(benzylamino)-2-deoxy-d-glycero-l-gluco heptonic acid (BnGa) were prepared and characterized by elemental analysis, thermal data, i.r., electronic and e.s.r. spectra, magnetic susceptibility measurements, and X-ray powder diffraction. The metal:ligand stoichiometry of these complexes is 12 and coordination around Cu^II seems to be octahedral, with the ligands bound through the N atom of the amino group and O atoms of the bridging carboxylate group.     

Reaction of α-bromocarboxylic acids with hydrazine and dimethylhydrazine

Nucleofilic reaction of a series of α-bromocarboxylic acids with hydrazine and dimethylhydrazine is studied. High reactivity of α-bromocarboxylic acids is revealed and a series of α-hydrazinoarboxylic acids and N-(1-carboxyalkyl)-N,N-dimethylhydrazinium bromides are synthesized.     

Topological evolution of cerium(Ⅲ) molybdate microflake assemblies induced by amino acids

In this work, cerium(Ⅲ) molybdate microspheres configured as microflakes were synthesized in the presence of lysine via a hydrothermal process. We studied the role of lysine and other amino acids on the morphologic control of cerium(Ⅲ) molybdate crystals. First, with the increase of lysine, thinner microflakes and smaller microspheres are obtained. Moreover, a transformation in topology of cerium(Ⅲ) molybdate assemblies from three-dimensional(3D) into two-dimensional(2D) can be ascribed to controlled nucleation and growth of cerium(Ⅲ) molybdate induced by lysine. Second, amino acids with strong hydrophilic ‘‘R' groups tend to induce nucleation and result in spherical assemblies formed by nanoparticles or nanoflakes, while those with weaker hydrophilic ‘‘R' groups tend to induce growth and yield spherical assemblies of microflakes.     

Copper(II) and oxovanadium(IV) complexes of α-hydroxymethylserine

Summary Potentiometric and spectroscopic measurements were used to characterize the binding ability of -hydroxy-methylserine (Hms) with copper(II) and oxovanadium(IV) ions. The ligand was found to be generally a more efficient chelating agent than serine. Both of the deprotonated hydroxyl groups of Hms can be involved in coordination to vanadyl ions, whereas copper(II) binds in the same way as with serine.     

Enantioselective recognition of α-hydroxycarboxylic acids and N-Boc-amino acids by counterion-displacement assays with a chiral nickel(II) complex

A new chiral sensor based on an N,N'-dioxide nickel(II) complex was prepared, which could visually recognize a series of chiral α-hydroxycarboxylic acid enantiomers by coordination and self-assembly forming into nanospheres or nanofibers. With the help of various techniques, the morphology structures of the colloid or suspension were obtained and the counterion-displacement assays were also confirmed. In addition, this metal complex could act as a highly enantioselective fluorescence sensor to recognize N-Boc-amino acids and chiral α-hydroxycarboxylic acids.     

One-pot gram-scale synthesis of γ-hydroxybutenolides through catalyst-free annulation of α-amino acids with α-keto acids in water

A one-pot gram-scale synthetic route for the preparation of γ-hydroxybutenolides via catalyst-free annulation of α-amino acids with α-keto acids in water is reported. The method shows many advantages such as readily available starting materials, mild reaction conditions, operational simplicity, acceptable yields, and requiring no extra catalysts or additions. Furthermore, the method is innocuous to the environment, also is valuable to industry.     

Reaction of 2-aminopyridines with α, β-unsaturated acids

The reaction of 2-amino- and 2-amino-5-halopyridines with acrylic, methacrylic, and crotonic acids forms N-(2-pyridyl)- and N-(5-halo-2-pyridyl)--alanines and the betaines 2-amino-1-(2-carboxylatoethyl)pyridinium or 3,4-dihydropyrido[1,2-a]pyrimidin-2-ones, or their homologs.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 1, pp. 80–85, January, 1992.     

Crystal structures of hafnium(IV) and zirconium(IV) complexes with β-diketones

Preparation methods are developed for a number of 7- and 8-coordinated derivatives of Hf(IV) and Zr(IV) with β-diketonate ligands (R¹-CO-CH-CO-R²). The complexes obtained are examined by IR spectroscopy, mass spectrometry, and X-ray crystallography. All structures are molecular. The M-O distances fall within 2.09–2.28 Å. In the crystals, the molecules are joined only by van der Waals interactions. It is demonstrated that the series of hafnium(IV) and zirconium(IV) chelates with identical ligands are isostructural, and the introduction of CF₃- or tert-butyl groups in the terminal positions of the ligand as well as chlorine substitution for one of the ligands do not essentially affect the basic geometric characteristics of the ligand in the complexes.     

Electrochemically mediated decarboxylative acylation of N-nitrosoanilines with α-oxocarboxylic acids

An efficient palladium-catalyzed electrooxidation C–H acylation reaction of N-nitrosoanilines with α-oxocarboxylic acids was developed. The anodic oxidation of the Pd(Ⅱ) intermediate was found to be the key to complete the reaction. In this case, the N-nitroso group was observed to be an effective directing group for C–H activation reaction. Moreover, the synthetic transformation of derivatives of natural products(L-menthol, dehydroepiandrosterone, and pregnenolone) was successfully realized. Fi...     

Synthesis of triterpene acids conjugates with α-tocopherol synthetic analogs

Heterodimers were synthesized of pharmacologically important α-tocopherol synthetic analogs with triterpene acids(betulonic, betulinic), potential polyfunctionsl drugs possessing antioxidant activity. The combination of the fragments of biologically active substances was performed through linkers (residues of succinic acid, hydrazine, glycine, tetramethylenediamine) binding the side chain of the antioxidant molecule with atoms C³ or C²⁸ of the terpenoid.     

Suzuki-Miyaura cross-coupling of α-phosphoryloxy enol ethers with arylboronic acids

The Suzuki-Miyaura cross-coupling reaction of cyclic ketene acetal phosphates with arylboronic acids was found to be a convenient and highly efficient method for the construction of aryl vinyl ethers. A wide variety of differentially substituted electron-poor and electron-rich arylboronic acids smoothly underwent the coupling process to provide the desired dihydropyrans in moderate to excellent yields.     

Enantio- and chemoselective differentiation of protected α-amino acids and β-homoamino acids with a single copper(II) host

The association between an achiral copper(II)-containing host 1 and chiral carboxylates has been expanded beyond previous studies to new chiral carboxylate guests, both α-amino acids and β-homoamino acids. The observed exciton-coupled circular dichroism (ECCD) signals for the enantiomers of each carboxylate were equal and opposite, and these signals differed in size and shape between the individual amino acids. Linear discriminant analysis (LDA) was applied as a statistical analysis technique to differentiate the amino acids, both enantioselectively and chemoselectively, giving the absolute configuration and identity of the amino acid. The identity of each of the α-amino acids and β-homoamino acids were determined independently by LDA, and then the two were considered together. Each of these analyses showed good differentiation of the amino acid guests with the use of only one host molecule.     

Synthesis of (α-substituted α-aminophosphinic and α-aminophosphonic acids

The reaction of ketoximes with hypophosphorous acid resulted in previously unknown -substituted--aminophosphinic acids, which were oxidized into the corresponding -substituted--aminophosphonic acids.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 11, pp. 2729–2732, November, 1996.     

Reactions of organometallics with oximes. Synthesis of α-N-hydroxy amino acids

Reaction of organolithium reagents with glyoxylate and pyruvate derived oximes provides a direct route for the synthesis of unusual α-N-hydroxy amino acids.     

New pentacoordinated Schiff-base diorganotin(IV) complexes derived from nonpolar side chain α-amino acids

In this work we report the synthesis and spectroscopic characterization of twenty new pentacoordinated diorganotin(IV) compounds. These compounds have been prepared in good yields by multicomponent reactions (MCRs) of α-amino acids (isoleucine, leucine, methionine, phenylalanine and aminophenylacetic acid), 2,4-dihydroxybenzaldehyde, 2-hydroxy-4-methoxybenzaldehyde and either di-n-butyltin(IV) oxide or diphenyltin(IV) oxide. All compounds were characterized by IR spectroscopy, ¹H, ¹¹⁹Sn and ¹³C NMR spectroscopy and mass spectrometry. Each compound has a coordinative N→Sn bond and shows the expected ¹¹⁹Sn NMR chemical shift indicative of a pentacoordinated or hexacoordinated tin atom in CDCl₃ and DMSO-d₆, respectively. These compounds were also tested in tumoral cell lines, HeLa, HCT-15 and MCF-7, in order to evaluate the antiproliferative activity and to obtain the medial inhibitory concentrations (IC₅₀) values.     

Stereoselective Pd-catalyzed synthesis of quaternary α-D-C-mannosyl-(S)-amino acids

In this paper, we report the stereoselective synthesis of α-D-C-mannosyl-(S)-amino acids exploiting, as a key step, an allylic alkylation of glycal-derived π-allyl Pd(II) intermediates, prepared by oxidative addition of Pd(0) species to 2,3-unsaturated pyranosides (pseudoglycals). The reaction of 4,6-di-O-acetyl α-pseudoglucal carbonate 10a with racemic alanine-, valine-, and phenylalanine-derived azlactones gave the corresponding (4S)-4-α-D-C-mannosyl-2-phenyloxazol-5(4H)-ones as the major diastereoisomers in high yields. The final α-D-C-mannosyl-(S)-amino acids were obtained in a few steps comprising highly diastereoselective dihydroxylation of the glucal derivative double bond followed by the one-pot hydrolysis of the benzamido and acetate protecting groups. Main features of this method are the conciseness of the synthetic sequence, the high diastereoselection of the allylic alkylation step, the use of racemic α-amino acids as starting material, and the good overall yields.