Total Synthesis of (-)-Baimuxifuranic Acid

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Synthesis of (R)-(-)-γ-amino β-hydroxy Butyric Acid (GABOB)

An efficient enantiospecific synthesis of a neuromodulator, antiepileplic and hypotensive drug (R)-(-)-γ-amino-β-hydroxybutyric acid (1) starting from (+) tartaric acid is described.     

Total Synthesis of (±)-Butyl Ester of Rosmarinic Acid

Rosmarinic acid, a well-known natural product firstly isolated from rosemary by Scarpati and Oriente in 19581, possesses various kinds of biological activities such as antioxidant2 and antibacterial3. Recently, the synthesis and biological activities of related compounds of rosmarinic acid have received much attention, such as 4, 4?′-O-di-β-D- glucopyranosyl rosmarinic acid4, methyl ester of rosmarinic acid5-6 and rabdosiin7. Butyl ester of rosmarinic acid 1 (Scheme 1) was isolated from Is…     

Efficient Synthesis of Biologically Active (±)‐Confluentin and (±)‐Daurichromenic Acid

One‐step synthesis of biologically active (±)‐confluentin is described from commercially available orcinol with trans,trans‐farnesal in the presence of ethylenediamine diacetate as a catalyst. Further conversion of synthetic confluentin to highly potent anti‐HIV agent, (±)‐daurichromenic acid, is accomplished by formylation and oxidation in two steps.     

Study on the Fluorescence System of Oxolinic Acid‐Tb(III) and the Determination of Oxolinic Acid

Abstract

In Tris‐HCl buffer (pH=7.43), Tb³⁺ can react with oxolinic acid (OA) and form a 1:2 complex, which emits the intrinsic fluorescence of Tb³⁺. Based on this, a new fluorimetric method of determination of OA is developed. Under the optimum conditions, the enhanced fluorescence intensity of the system is proportional to the concentration of OA in the range of 1.5×10^?7～2.5×10^?5mol/L, and the detection limit is 5.5×10^?9 mol/L. Recovery test was also satisfactory. The experiments indicated that the luminescence mechanism was attributed to the M*–M luminescence.     

Two Novel Mercury(Ⅱ) and Copper(Ⅱ) Complexes Based on(5-Chloro-quinolin-8-yloxy)acetic Acid

Two novel mononuclear complexes with 5-chloro-8-(methoxycarbonylmethoxy)quinoline ligand(L), namely, HgLBr_2 1 and CuL_2Cl_2 2, have been prepared by solvothermal reaction of(5-chloro-quinolin-8-yloxy)acetic acid with HgBr_2 and CuCl_2, respectively. Their structures were characterized by IR, elemental analysis, UV-Vis-NIR spectra, TG and single-crystal X-ray diffraction analysis. Interestingly,(5-chloro-quinolin-8-yloxy)acetic acid is changed as 5-chloro-8-(methoxycarbonylmethoxy)quinoline ligand(L) in complexes 1 and 2. Crystal data for 1: C12H10Br2 Cl Hg NO3, Mr = 612.07, triclinic, space group P1 with a = 8.5983(7), b = 9.7726(6), c = 10.1549(6) ?, α = 66.355(6), β = 77.067(8), γ = 78.803(8)°, V = 756.6(9) ?3, Z = 2, Dc = 2.687 g/cm3, F(000) = 560, μ = 15.633 mm-1, R = 0.0351 and w R = 0.0504. Crystal data for 2: C24H20Cl4 Cu N2O6, Mr = 637.76, triclinic, space group P1 with a = 10.5324(9), b = 11.2377(16), c = 12.0143(12) ?, α = 83.413(11), β = 64.475(9), γ = 83.144(11)°, V = 1270.9(2) ?3, Z = 2, Dc = 1.667 g/cm3, F(000) = 646, μ = 1.324 mm-1, R = 0.0408 and w R = 0.0922. In 1, the HgII centre is a distorted trigonal planar geometry comprised of two Br atoms and one quinoline N atom of L. Intermolecular π-π, C–H···π stacking interactions and intermolecular C–H···Br hydrogen bonds are observed in the molecular packing of 1. In complex 2, each CuII center has a distorted octahedral geometry comprised of two chloride ions, two quinoline N atoms and two O atoms of two L ligands. Intermolecular C–H···Cl hydrogen bonds exist in the molecular packing of 2. The fluorescence emission peak of complexes 1 and 2 appears near 406 and 410 nm, respectively. Optical diffuse-reflection spectral results suggest complex 1 has the property of semiconductor.     

Synthesis and Catalytic Activity of Copper(Ⅱ) Resorcylic Acid Nanoparticles

Copper(Ⅱ) resorcylic acid(CuRes) nanoparticles were synthesized by using reactive precipitation method with resorcylic acid and blue copperas as the raw material in a rotating packed bed. The sample obtained was characterized by using X-ray diffraction( XRD), transmission electron microscopy( TEM ), Fourier transform infrared spectroscopy (FTIR), thermo-gravimetric analyses (TG), and element analysis. In addition, the catalytic activity of CuRes nanoparticles on the thermal decomposition of nitrocellulose-nitroglycerine (NC-NG) was also determined via DSC.The results show that the spherical nanoparticles with a diameter of 20 nm were obtained in ethanol solution. The peak temperature of the thermal decomposition of NC-NG-CuRes decreases by 3 ℃ compared with that of normal CuRes,and the decomposition enthalpy is increased by 735 J/g, and therefore, it is reasonable to assume that CuRes nanoparticles have a better catalytic activity.     

New and Concise Approach to (R)-α-Lipoic Acid

A concise enantiospecific synthesis of (S)-6,8-bis(methylsulfonyloxy)-octanoic acid (2), a ready precursor of (R)-(+)-α-lipoic acid (1), is reported. The key step of the synthesis is the coupling of the tosylate derived from (R)-malic acid with phenylpropyl magnesium bromide. A recently reported green procedure was used for the oxidative unmasking of the phenyl group, used as a latent carboxyl group.     

A Convenient Synthesis of 2,4(3H,5H)-Furandione (β-Tetronic Acid)

The chemical versatility of 2,4(3H,5H)-furandione (β-tetronic acid, 1) and its synthetic applicability are of considerable current interest^1b,2a-k. The multifunctional character of this small molecule confers an intriguing synthetic potential which has prompted us to develop synthetic schemes utilizing it as a synthon for certain heterocyclic systems.     

A New Luminescent Cd(Ⅱ) Coordination Polymer Constructed with 2-(Carboxymethoxy) benzoic Acid

In this work, we synthesized a new Cd(Ⅱ) coordination polymer, [Cd(L)(cmb)H_2O]· H_2O(1), by using mixed 2-(carboxymethoxy)benzoic acid(H2 cmb) and typical chelating N-donor ligands 2-(2-fluoro-6-fluorophenyl)-1 H-imidazo[4,5-f][1,10]phenanthroline ligand(L). 1 crystallizes in monoclinic, space group P21/c with a = 17.6150(8), b = 9.7811(4), c = 18.1603(8) ?, β = 118.9150(10)o, V = 2738.9(2) ?~3, Z = 4, C28 H20 CdF2 N4 O7, Mr = 674.88, Dc = 1.637 g/cm3, F(000) = 1352, μ(Mo Ka) = 0.865 mm–1, R = 0.0643 and w R = 0.1976. In 1, the cmb2– anions link neighboring Cd(Ⅱ) atoms in a bis-chelating mode, yielding a one-dimensional chain structure along the b axis. The L ligands are attached on one side of the chain through chelating the Cd(Ⅱ) atoms, and are stacked with those of an adjacent chain through π-π interactions to generate a one-dimensional double-chain structure. Furthermore, the one-dimensional double-chains are stacked by C–H???π interactions between the carbon atom of L ligand and the benzene ring of cmb2–ligand to give a layer structure. Moreover, the solid state luminescent property of 1 was also investigated at room temperature.     

Oligomeric Derivatives of 3α,7β-D Ihydroxy-5β-Cholan-24-Oic Acid (Ursodeoxycholic Acid)

The synthesis and pharmacological evaluation of Oligomeric and polymeric derivatives of drugs is receiving increasing attention by several groups ^1-9. Usually, in these derivatives, the drug moieties are linked to a proper oligomeric or polymeric matrix by means of covalent bonds of limited stability to biological environments. This may ensure a gradual release of the active principle after introduction into the body Fluids. Poly(oxyethyleneglycol)s, as matrices, appear to be particularly promising on this respect⁷.     

Silica Sulfuric Acid,an Efficient and Recyclable Solid Acid Catalyst for the Synthesis of 4,4′-(Arylmethylene)bis (1H-pyrazol-5-ols)

Silica sulfuric acid (SSA) is employed as a recyclable catalyst for the condensation reaction of aromatic aldehydes with 3-methyl-l-phenyl-5-pyrazolone. This condensation reaction is performed in a mixture (1:1 v/v) of water–ethanol at 70 °C, giving 4,4′-alkylmethylene-bis(3-methyl-5-pyrazolones) in 75–93% yields.

(Salen)Ti(IV)-Catalyzed Asymmetric Ring-opening of meso Epoxides Using Dithiophosphorus Acid as the Nucleophile

As an important strategy for the formation of 1,2-bifunctionalized systems theasymmetric ring-opening of epoxides with different nucleophiles has drawn muchattention from the organic chemists. A wide variety of nucleophiles are utilized in theaforemention…     

α-Amino-iso-Butyric Acid Foldamers Terminated with Rhodium(I) N-Heterocyclic Carbene Catalysts

To investigate how remotely induced changes in ligand folding might affect catalysis by organometallic complexes, dynamic α-amino-iso-butyric acid (Aib) peptide foldamers bearing rhodium(I) N-heterocyclic carbene (NHC) complexes have been synthesized and studied. X-ray crystallography of a foldamer with an N-terminal azide and a C-terminal Rh(NHC)(Cl)(diene) complex showed a racemate with a chiral axis in the Rh(NHC) complex and a distorted 3₁₀ helical body. Replacing the azide with either one or two chiral L-α-methylvaline (L-αMeVal) residues gave diastereoisomeric foldamers that each possessed point, helical and axial chirality. NMR spectroscopy revealed an unequal ratio of diastereoisomers for some foldamers, indicating that the chiral conformational preference of the N-terminal residue(s) was relayed down the 1 nm helical body to the axially chiral Rh(NHC) complex. Although the remote chiral residue(s) did not affect the stereoselectivity of hydrosilylation reactions catalysed by these foldamers, these studies suggest a potential pathway towards remote conformational control of organometallic catalysts.     

Synthesis and Crystal Structure of Di-n-butyltin(IV) Complex with 2-Oxo-propionic Acid (4-Pyridinecarbonyl) Hydrazone

Introduction The studies of diorganotin(IV) complexes are of current interest owing to their wide range of applica-tions such as biocides and homogeneous catalysts in industry.1 In recent years there have been more and more reports on the synthesis, antitumour activities and structural elucidation of various diorganotin(IV) deriva-tives of carboxylic acid.2-5 In particular, people take considerable interest in structural studies of diorgano-tin(IV) complexes of carboxylic acid, because there…     

Intramolecular Cyclization of 1-(ω-Phenylalkyl)-2-(nitromethylene)pyrrolidines in Triflic Acid

1-(ω-Phenylalkyl)-2-(nitromethylene)pyrrolidines in triflic acid undergo a C,O-diprotonation, followed by loss of water, to form conjugated iminium–hydroxynitrilium dications, which react with the tethered phenyl ring by electrophilic aromatic substitution to afford tricyclic iminium compounds as triflate salts. The scope and mechanism of this reaction are discussed.     

Tb(lll) and Ca(ll) Ion Equilibria in the Presence of Glutamic Acid and Glutamine

Bio1caica1effectSofmeartharecloselyrelathetOtheoriesofrareewth,sothestudiesonthesweiesofmorthareofereirtlei~tanCeL1,2J'Asacontinuationofourrerch[3j,inthiswrkweStodiedfo(ll1)andfa(ll)ionequilibriainthe~ceofglubeicacid(Glu)andglUhaire(Gln)at37tedanionicstwiofo.l5so1/L(HaCl)byPothetiwetrictithetion.PotentioretrictitrationnsWfedasforiforweviasly[3j.ffeorisentoldstswetreatedonmem386/the-terusingpeguze2[41.theoouilibeiainthestudiedsySteasandcorreSPOndingnOtetionfOrthestabi1ityconsthetSaregiv…     

A Green Synthesis of 2-Ethylanthraquinone by Dehydration of 2-(4''''-ethylbenzoyl) benzoic Acid over Solid Acid Catalysts

2-EAQ is an important intermediate for the synthesis of hydrogen peroxide, pharmaceu- ticals, pesticides, and dyes. With the increasing demand for hydrogen peroxide, it needs to enhance the yields of 2-EAQ. However, in the conventional process, concentrated H2SO41-2 is employed as the catalyst in the dehydration of BE acid for the synthesis of 2-EAQ, which produces a series of environmental impacts and safety concerns. For these reasons, a substitute process, which has little or no hazard…     

The Case of Formic Acid on Anatase TiO2(101): Where is the Acid Proton?

Carboxylic‐acid adsorption on anatase TiO₂ is a relevant process in many technological applications. Yet, despite several decades of investigations, the acid‐proton localization—either on the molecule or on the surface—is still an open issue. By modeling the adsorption of formic acid on top of anatase(101) surfaces, we highlight the formation of a short strong hydrogen bond. In the 0 K limit, the acid‐proton behavior is ruled by quantum delocalization effects in a single potential well, while at ambient conditions, the proton undergoes a rapid classical shuttling in a shallow two‐well free‐energy profile. This picture, supported by agreement with available experiments, shows that the anatase surface acts like a protecting group for the carboxylic acid functionality. Such a new conceptual insight might help rationalize chemical processes involving carboxylic acids on oxide surfaces.