Synthesis of 1,3-thiazoline derivatives from β-dicarbonyl compounds and phenacyl thiocyanate

Acetylacetone and ethyl acetoacetate undergo addition at the CN bond of phenacyl thiocyanate in the presence of Ni(acac)₂ to give the respective keteneN, S-acetals, which undergo smooth cyclization to afford 2-methylene-4-phenyl-1, 3-thiazoline derivatives when refluxed in THF.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 11, pp. 1938–1940, November, 1993     

Selective reduction of the acyl group in cyclic α-acyl-β-dicarbonyl compounds with sodium cyanoborohydride. Efficient synthesis of cyclic α-alkyl-β-dicarbonyl compounds

Efficient synthesis of cyclic -alkyl--dicarbonyl compounds of the cyclopentane, cyclohexane, tetronic acid, and -pyrone series from the corresponding cyclic -acyl--dicarbonyl compounds under the action of NaBH₃(CN) in a THF--HCl system is described.     

Interaction of aminals of conjugated ω-dimethylaminoaldehydes with cyclic β-dicarbonyl compounds

Reactions of aminals of conjugated -dimethylaminoaldehydes with Meldrum's acid,N,N-(o-phenylene)malonamides, and 2,3-dihydrophenalene-1,3-dione afford -dimethylaminodienones, substituted 2-dimethylamino-2H-pyrans, or oxanine salts. Cation-anionic polymethine dyes have been obtained from the latter.Translated fromIzyestiya Akademii Nauk. Seriya Khimicheskaya, No. 2, pp. 285–288, February, 1994.     

Sulfuric acid catalyzed addition of β-dicarbonyl compounds to alcohols under conventional heating and microwave-assisted conditions

The highly efficient direct addition of β-dicarbonyl compounds to secondary alcohols has been achieved using one of the cheapest acids, H₂SO₄, as the catalyst. For a series of β-dicarbonyl compounds and various secondary alcohols, the addition reactions all complete in 5 min with high yields both under the conventional heating condition and under the microwave heating condition. The comparison of the results obtained from the microwave heating condition with those obtained from the conventional heating condition shows that no obvious specific or nonthermal microwave effects exist in the microwave-assisted addition reactions.     

Aliphatic acid dihydrazide derivatives of dicyclopentadienylzirconium(IV) dichloride and their reactions with β-diketones. Formation of cyclic compounds

The reactions of dicyclopentadienylzirconium(IV) dichloride with bidentate aliphatic acid dihydrazide (LH₂) derived from oxalic, succinic, and adipic acids (metal to ligand molar ratios 1 : 1 and 1 : 2, respectively) in anhydrous tetrahydrofuran in the presence of base led to the formation of the [Cp₂Zr(L)] and [CpZr(LH)₂Cl] complexes. The complexes were characterized by elemental analyses, electrical conductance, magnetic measurements and spectroscopic studies. These ligands appear to behave as bidentate chelate agents. All the complexes contain terminal amino or terminal hydrazinc nitrogen atoms with an unshared electron pair, enabling nucleophilic condensations. Therefore, the reactions of these complexes with β-diketones (acetylacetone, benzoylacetone, dibenzoylmethane, thenoyltrifluoroacetone) in the presence of glacial acetic acid have been studied viz., ring closure and formation of macrocyclic ligand (mac) complexes. Two types of cyclic products viz., [Cp₂Zr(mac)] and [CpZr(Mac)Cl] were isolated. The spectral studies of these cyclic products are reported.     

Synthesis of C3-nitroalkylated-4-hydroxycoumarin and hydroxyiminodihydrofuroquinolinone derivatives via the Michael addition of cyclic 1,3-dicarbonyl compounds to β-nitrostyrenes

Herein, we describe a practical and efficient method for the C3-alkylation of 4-hydroxycoumarin by sonication under ‘on water’ conditions and mild temperatures using various substituted β-nitrostyrenes. In addition, we report on the development of a convenient process for the regioselective synthesis of angular hydroxyiminodihydrofuroquinolinone catalyzed by base. 4-Hydroxycoumarin and 4-hydroxy-1-methylquinolin-2(1H)-one reacted smoothly with various nitroolefins to furnish C3-nitroalkylated hydroxycoumarin derivatives (by sonication and ‘on water’ conditions) and hydroxyiminodihydrofuroquinolinone derivatives (ambient condition) as a mixture of Z (minor) and E (major) isomers, respectively. The mild reaction conditions employed, ease of isolation of the products and excellent yields constitute important features of the methodology.     

Mono-acylation of a polyamine-β-cyclodextrin based on guest mediated acyl migration

The S → N acylation rates of thioester functionalized coumarins on heptakis-[6-deoxy-6-(2-aminoethylsulfanyl)]-β-cyclodextrin were measured. A high yield of mono-acylation was achieved with products that form self-inclusion compounds. The differential fluorescence response of the functionalized cyclodextrins upon binding biomacromolecules shows the potential of the constructs as probes.     

Synthesis of β-aroylvinyl derivatives of triphenylphosphine and pyridine based on β-aroylacrylic acids

Bromination of β-aroylacrylic acids afforded β-aroyl-α,β-dibromopropionic acids. The latter reacted with pyridine to form 1-(β-aroylvinyl)pyridinium bromides. Reaction of the salts obtained with triphenylphosphine resulted in β-aroylvinyltriphenylphosphonium bromides.     

Intramolecular ester enolate-imine cyclization reactions for the asymmetric synthesis of polycyclic β-lactams and cyclic β-amino acid derivatives

Enolates of chiral N-(α-methyl-p-methoxybenzyl)-ω-imino-esters undergo intramolecular cyclization reactions to afford (syn)-aza-anions of β-amino esters in high dr that cyclize to afford N-(α-methyl-p-methoxybenzyl)-β-lactams that can be readily deprotected to afford their corresponding cyclic NH-β-lactams, β-amino esters, or β-amino acids.     

Towards cyclic,conformationally constrained,fluorine-containing β-amino acid derivatives from d-glucose

Novel, potentially bioactive, fluorinated branched-chain monosaccharides were obtained by reaction of diethylaminosulphur trifluoride (DAST) with a series of methyl 3-C-cyano-3-ethoxycarbonyl-β-d-glucopyranoside derivatives, including the 4,6-O-benzylidene derivative and their 3-C-(N-protected aminomethyl) reduction products, as well as the phenyl 3-C-cyano-3-ethoxycarbonyl-1-thio-α-d-(and β-d-)glucopyranosides. The absolute configuration at C(3) was unambiguously assigned for all compounds on the basis of X-ray crystallographic analysis of methyl 4,6-O-benzylidene-3-C-cyano-3-deoxy-3-ethoxycarbonyl-β-d-glucopyranoside, corroborating the previous tentative assignment by other authors for the 4,6-unprotected compound. The course of the fluorination depended on the reaction temperature and the substitution pattern of the substrate. Thus, for methyl 3-C-cyano-3-ethoxycarbonyl-β-d-glucopyranoside, fluorination occurred exclusively at C(6), but for the phenylthio analogue, a 2-deoxy-2-phenylthio-α-d-manno-configured glycosyl fluoride and its 6-fluoro derivative were obtained, resulting from the expected rearrangement reaction, whilst starting from the phenylthio α anomer, only the unrearranged 6-fluoro compound was formed. Rearrangement was also observed in the fluorination of methyl 4,6-O-benzylidene-3-C-(N-protected aminomethyl)-β-d-glucopyranoside, which led to the 2-O-methyl-α-d-mannopyranosyl fluoride derivative as the sole product. This methodology may constitute a simple route to enantiopure conformationally constrained cyclic fluorinated β-amino acids having the α carbon atom shared with a pyranose ring, although only moderate yields were achieved, particularly in the fluorination step.     

Lipase mediated sequential resolution of aromatic β-hydroxy esters using fatty acid derivatives

The lipase-catalyzed kinetic resolution of a series of aromatic β-hydroxy esters in organic media has been investigated. Decanoic acid and its esters were successfully used as acyl donors for selective O-acylation. The regio- and enantioselective enzymatic hydrolysis of the decanoate moiety of the diesters was also investigated. The effects of water, reaction temperature, and solvent type, and also the influence of substrates structure on the catalytic behavior of potential commercially available lipases were studied. A novel procedure was developed for the efficient and highly stereoselective synthesis of both enantiomers of both novel and known target compounds.     

3D-QSAR and docking studies of estrogen compounds based on estrogen receptor β

Close attention has been paid to estrogen compounds because these chemicals may pose a serious threat to the health of humans and wildlife. Estrogen receptor (ER) exists as two subtypes, ERα and ERβ. The difference in amino acids sequence of the binding sites of ERα and ERβ might lead to a result that some synthetic estrogens and naturally occurring steroidal ligands have different relative affinities and binding modes for ERα and ERβ. In this investigation, comparative molecular similarity indices analysis...     

Synthesis and characterization of novel β-amino acid derivatives

In the work discussed in this paper, novel β-amino acid derivatives were prepared by Michael addition between 3-substituted-2-propenic acid and hydrazine hydrate. The optimum reaction conditions were determined by analyzing the effects of the ratio of the starting materials, temperature, and reaction time. The conclusions were: reaction temperature 80 °C, reaction time 8 h, n (3-substituted-2-propenic acid)/n (hydrazine hydrate) = 1:15. Products were characterized by measurement of melting point, elemental analysis, and IR and ¹H NMR spectroscopy.     

A study of the tautomerism of β-dicarbonyl compounds with special emphasis on curcuminoids

Six β-diketones related to curcumin and curcumin itself have been studied by ¹³C NMR spectroscopy in chloroform in order to determine the equilibrium constant between the two keto/enol tautomers. In order to do this GIAO/B3LYP/6-31G^∗∗ calculations of absolute shieldings (σ, ppm) were carried out. To establish relationships between σ and experimental chemical shifts (δ, ppm), three simple β-diketones (acetylacetone, dibenzoylmethane and benzoylacetone) have been studied. The preference for different groups to be conjugated with the CO has been determined.     

Isolation of C₁₁ compounds and a cyclopropane fatty acid from an Okinawan ascidian, Diplosoma sp

Pentylphenols 1 and 2, cyclopropane fatty acid 3, and cyclopentenones 4 and 5, were isolated from an ascidian, Diplosoma sp. The structures of 1-5 were determined by spectroscopic analysis and/or synthesis. Compound 1 inhibited the division of fertilized sea urchin eggs and compound 4 showed mild cytotoxity against HCT116 cells (human colorectal cancer cell).     

Synthesis of enantiopure (αMe)Dip and other α-methylated β-branched amino acid derivatives

This report describes the synthesis of the two enantiomerically pure α-methylated β-branched phenylalanine derivatives, (S)- and (R)-α-methyl-β,β-diphenylalanine—(αMe)Dip—starting from the chiral building blocks (R)- and (S)-N-Boc-N,O-isopropylidene-α-methylserine methyl esters, respectively. The key step involves a double alkylation with a Grignard reagent on an ester group. The use of the same protocol for the preparation of other α-methylated β-branched serine derivatives is also described.     

Syntheses and characterization of two new compounds based on versatile 1,2,3,5-benzenetetracarboxylic acid and 2,2′-bibenzimidazole

Two coordination complexes based on H₄btec and H₂bibzim (H₄btec = 1,2,3,5-benzenetetracarboxylic acid, H₂bibzim = 2,2′-bibenzimidazole), [Ni(H₂bibzim)₃]₂(btec) (1) and [Zn(H₂bibzim)(btec)_0.5]_n (2), have been synthesized by hydrothermal methods and characterized by single-crystal X-ray diffraction. Complex 1 is composed of [Ni(H₂bibzim)₃]²⁺ with free btec^4? as counter anion. In 2, the btec^4? ligands bridge the Zn(II) ions into a 1-D chain with H₂bibzim as auxiliary chelating ligands. Interesting supramolecular structures were demonstrated due to the existence of hydrogen bonding as well as π?π interactions in the two different complexes. The H₂bibzim ligands act as a 2-connected spacer in both complexes. However, in 1, the [Ni(H₂bibzim)₃]²⁺ cations act as 3-connected nodes, hydrogen bonded with the 6-connected btec^4? ligands into a 3-D framework with (3,6)-connected topology Schläfli symbol as (4.6.8)(4².6)(4³.6⁴.8⁷.10). As for 2, Zn serves as a 3-connected node with btec^4? as a 6-connected node, leading to a 2D (3,6)-connected hydrogen bonding kgd topology sheet with Schläfli symbol of (4³)²(4⁶.6⁶.8³). Thermal stabilities and photoluminescent properties of 1 and 2 were also studied.     

Efficient preparation of β-hydroxy aspartic acid and its derivatives

We reported an efficient and practical synthetic route to various properly-protected erythreo-β-OH-Asp compounds, which are key β-branched a-amino acid units in coralmycin A and other peptide natural products.