Binding behavior of amino acid conjugates of indole-3-acetic acid to immobilized human serum albumin

The affinity of indole-3-acetic acid (IAA), indole-3-propionic acid, indole-3-butyric acid and 24 of their amino acid conjugates to immobilized human serum albumin, as expressed by the retention factor k (determined by HPLC), was dependent on (1) lipophilicity, (2) chirality and (3) functional groups in the amino acid moiety; in some cases conformation plays an additional role. Two lipophilicity-related parameters afforded quantitative correlations with k: retention on a C18 reversed-phase column (experimental approach) and the distance between the hydrophilic and hydrophobic poles of the molecules (in silico approach). Most compounds examined are possible metabolic precursors of IAA, an experimental tumor therapeutic.     

A Concise Semi-Synthetic Approach to Betulinic Acid from Betulin

Betulin was convert to betulinic acid using two different synthetic routes. The first approach involved an oxidation of betulin using Jones' reagent to betulonic acid and subsequent NaBH₄ reduction to betulinic acid. The second approach involved steps utilizing different protecting groups on the alcohol functional groups of betulin and Jones' oxidation to circumvent the isomerization of the secondary alcohol of betulinic acid.     

Determination of copper, cadmium, lead and bismuth in phosphoric acid solutions by atomic-absorption spectrometry after extraction with diethylammonium diethyldithiocarbamate and butyl acetate

The possibility of applying diethylammonium diethyldithiocarbamate and butyl acetate for the extraction of copper, cadmium, lead and bismuth from molar solutions of orthophosphoric acid, and from solutions containing up to 55% pyrophosphoric acid and 20% tripolyphosphoric acid has been investigated. Some characteristics of the various diethylammonium diethyldithiocarbamate-butyl acetate-phosphoric acid systems are described. Suitable conditions have been found for flame atomic-absorption spectrometric determination of the ions extracted. This extraction/AAS approach has been used to determine copper, cadmium, lead and bismuth in some iron-, aluminium- and tin-containing samples dissolved in concentrated orthophosphoric acid. The same approach is used for determining 10(-5)-10(-6)% copper, cadmium and lead in orthophosphoric acid and in alkali-metal mono and dihydrogen phosphates.     

Vacancy ion-exclusion chromatography of haloacetic acids on a weakly acidic cation-exchange resin

A new and simple approach is described for the determination of the haloacetic acids (such as mono-, di- and trichloroacetic acids) usually found in drinking water as chlorination by-products after disinfection processes and acetic acid. The new approach, termed vacancy ion-exclusion chromatography, is based on an ion-exclusion mechanism but using the sample solution as the mobile phase, pure water as the injected sample, and a weakly acidic cation-exchange resin column (TSKgel OApak-A) as the stationary phase. The addition of sulfuric acid to the mobile phase results in highly sensitive conductivity detection with sharp and well-shaped peaks, leading to excellent and efficient separations. The elution order was sulfuric acid, dichloroacetic acid, monochloroacetic acid, trichloroacetic acid, and acetic acid. The separation of these acids depends on their pKa values. Acids with lower pKa values were eluted earlier than those with higher pKa, except for trichloroacetic acid due to a hydrophobic-adsorption effect occurring as a side-effect of vacancy ion-exclusion chromatography. The detection limits of these acids in the present study with conductivity detection were 3.4 microM for monochloroacetic acid, 0.86 microM for dichloroacetic acid and 0.15 microM for trichloroacetic acid.     

Iridium-catalyzed direct ortho-C–H amidation of benzoic acids with sulfonylazides

A mild and efficient iridium-catalyzed ortho-C–H amidation with sulfonyl azides by weakly coordinating carboxylic acid was demonstrated, which provided a novel approach to anthranilic acid derivatives.     

UHPLC–MS/MS quantification combined with chemometrics for the comparative analysis of different batches of raw and wine‐processed Dipsacus asper

A rapid and sensitive ultra‐high performance liquid chromatography with tandem mass spectrometry approach was established for the simultaneous determination of 4‐caffeoylquinic acid, loganic acid, chlorogenic acid, loganin, 3,5‐dicaffeoylquinic acid, dipsacoside B, asperosaponin VI, and sweroside in raw and wine‐processed Dipsacus asper . Chloramphenicol and glycyrrhetinic acid were employed as internal standards. The proposed approach was fully validated in terms of linearity, sensitivity, precision, repeatability as well as recovery. Intra‐ and interassay variability for all analytes were 2.8–4.9 and 1.7–4.8%, respectively. The standard addition method determined recovery rates for each analytes (96.8–104.6%). In addition, the developed approach was applied to 20 batches of raw and wine‐processed samples of Dipsacus asper . Principle component analysis and partial least squares‐discriminate analysis revealed a clear separation between the raw group and wine‐processed group. After wine‐processing, the contents of loganic acid, chlorogenic acid, dipsacoside B, and asperosaponin VI were upregulated, while the contents of 3,5‐dicaffeoylquinic acid, 4‐caffeoylquinic acid, loganin, and sweroside were downregulated. Our results demonstrated that ultra‐high performance liquid chromatography with tandem mass spectrometry quantification combined with chemometrics is a viable method for quality evaluation of the raw Dipsacus asper and its wine‐processed products.     

离散小波变换-支持向量回归方法同时测定苯酚、苯胺和苯甲酸

在波长范围200～400nm测定苯酚、苯胺和苯甲酸混合液的吸收光谱,用离散小波变换（DWT）对光谱数据进行处理,再用支持向量回归SVR方法进行建模,建立了离散小波变换一支持向量回归方法（DWT—SVR）。方法用于模拟样品和污染水样中苯酚、苯胺和苯甲酸的同时测定,结果满意。     

3-氨基环己基甲酸和cis-3-氨基环己烯基-5-甲酸立体异构体的合成

通过手性胺拆分方法，从3-环己烯基甲酸出发分别合成得到了3-氨基环己基甲酸（ACHC）的四个立体异构体，以及cis-5-氨基-3-环己烯基甲酸（ACHEC）的二个立体异构体。     

A concise approach to 5-substituted-4-pyrones from kojic acid

A concise approach to 5-substituted-4-pyrones is described. This approach is based on manipulation of the 5-hydroxy group of readily available kojic acid. A number of 5-substituted-4-pyrones were synthesized from kojic acid utilizing Heck reaction, Suzuki coupling and Stille coupling.     

Enantiodivergent total synthesis of microcarpalide from l-tartaric acid

Stereoselective approach for the synthesis of both enantiomers of bio-active decanolactone microcarpalide is described from l-tartaric acid. The synthesis of the key intermediates en route to the natural product is achieved from l-tartaric acid involving the elaboration of γ-hydroxy amide derived from tartaric acid and ring opening of an epoxide derived from tartaric acid.     

New Approach to Synthesis of 6,7—Dimethoxyisatin

A new approach to synthesis of 6,7-dimethoxyisatin is reported.2-nitro-3,4-dimethoxy mandelonitrile in glacial acetic acid was treated with the solution of stannous chloride in hydrochloric acid to give 6,7-dimethoxyisatin in a high yield.     

New Insight into the Synthesis and Biological Activity of the Polymeric Materials Consisting of Folic Acid and β‐Cyclodextrin

This work presents a very new look at folate targeting and is focused on synthesizing and assessing the biological activity of folic acid‐targeted drug delivery materials based on β‐cyclodextrin. Both folic acid and β‐cyclodextrin have been covalently conjugated to branched polyethylenimine as the polymeric vector. Host–guest inclusion of folic acid into a β‐cyclodextrin cavity, demonstrated by means of the spectroscopic methods (2‐D NMR, IR, UV–Vis), is found to be of crucial importance for biological activity of nanotherapeutics. This paper describes the very first example of the versatile synthetic approach to create the polymeric biosystems, where folic acid activity is not limited by the inclusion phenomenon. Cytotoxicity of the obtained polymeric materials against Lewis lung carcinoma cells is determined by neutral red uptake assay. Folate receptor‐binding studies reveal that the developed synthetic approach enables full exploitation of the potential of folic acid as a targeting ligand.     

New approach to processing of the apatite concentrate

New approach to processing of the apatite concentrate is suggested and substantiated. The approach includes treatment of the concentrate with a phosphoric acid solution at room temperature in the presence of a sulfo cation exchanger in the NH₄⁺ or H⁺ form. The phosphoric acid solution and the sorbent saturated with metal cations are separated and processed into target products by the known methods. The advantages and disadvantages of the approach are discussed.     

Predicting Mole‐Fraction‐Dependent Dissociation for Weak Acids

We demonstrate for formic and acetic acid dissolved in water as examples that the binary quantum cluster equilibrium (bQCE) approach can predict acid strengths over the whole range of acid concentrations. The acid strength increases in a complex rather than a simple way with increasing mole fraction of the acid from 0 to 0.7, reflecting the complex interplay between the dissociated ions or conjugate bases available as compared to the acid and water molecules. Furthermore, our calculated ion concentrations meet the experimental maximum of the conductivity with excellent agreement for acetic acid and satisfactorily for the formic acid/water mixture. As only a limited number of simple quantum‐chemical calculations are required for the prediction, bQCE is clearly a valuable approach to access these quantities also in non‐aqueous solutions. It is a highly valuable asset for predicting ionization processes in highly concentrated solutions, which are relevant for biological and chemical systems, as well as technological processes.     

Total Synthesis of Resorcylic Acid Lactone (−)-Neocosmosin A Using Palladium-Catalyzed α-Arylation of Enones as the Key Step

The total synthesis of the 14-membered resorcylic acid lactone neocosmosin A is described. The key step in the synthesis is the palladium-catalyzed α-arylation of TES-enol ethers of enones. The employment of the α-arylation approach to this class of resorcylic acid lactones is a new approach, which has the scope of being generalized into a unified approach for the synthesis of this class of natural products.     

Efficient synthesis of thioglycosylated kojic acid by s-glycosyl isothiouronium salts

In this study, 7-S-glycosides of kojic acid were designed and synthesized as mimics of its 7-O-glycosides to improve its water solubility and metabolic stability. To achieve this synthesis, a one-pot approach involving S-glycosyl isothiouronium salts generated in situ as key intermediates was developed by using 7-chloro-kojic acid as the alkylation reagent. A series of water soluble 7-S-glycosides of kojic acid, incorporating monosaccharides and disaccharides, were prepared using this protocol. Thus, this work offers a mild, convenient, and efficient approach for the synthesis of 7-S-glycosides of kojic acid in medium to good yields.     

Enzymatic C-terminal amidation of amino acids and peptides

Herein, we describe two versatile and high yielding enzymatic approaches for the conversion of semi-protected amino acid and peptidyl C-terminal α-carboxylic acids into their corresponding amides. In the first approach, the lipase Candida antarctica lipase-B (Cal-B), and in the second approach, the protease Subtilisin A, are used, respectively. We found that by using the ammonium salt of the α-carboxylic acid instead of separate ammonia sources, the enzymatic amidation reactions proceeded much faster without side reactions and gave near to quantitative yields of products.     

Expanding the genetic code of yeast for incorporation of diverse unnatural amino acids via a pyrrolysyl-tRNA synthetase/tRNA pair

We report the discovery of a simple system through which variant pyrrolysyl-tRNA synthetase/tRNA(CUA Pyl) pairs created in Escherichia coli can be used to expand the genetic code of Saccharomyces cerevisiae. In the process we have solved the key challenges of producing a functional tRNA(CUA Pyl) in yeast and discovered a pyrrolysyl-tRNA synthetase/tRNA(CUA Pyl) pair that is orthogonal in yeast. Using our approach we have incorporated an alkyne-containing amino acid for click chemistry, an important post-translationally modified amino acid and one of its analogs, a photocaged amino acid and a photo-cross-linking amino acid into proteins in yeast. Extensions of our approach will allow the growing list of useful amino acids that have been incorporated in E. coli with variant pyrrolysyl-tRNA synthetase/tRNA(CUA Pyl) pairs to be site-specifically incorporated into proteins in yeast.     

Choice of the optimal synthetic approach for the polypeptide ligands of prostatic specific membrane antigen preparation

Two alternative synthetic schemes involving solid-phase peptide synthesis steps for the preparation of prostatic specific membrane antigen ligands based on Glu-Urea-Lys with peptide fragments in the linker structure are compared. In the first approach, the amino acid key intermediate is attached to the 2-CTC resin by the carboxy group while in the second approach, by the amino one. The preference for each approach is dependent on the particular target molecule     

Synthesis of 4-azo-butenolides

An efficient, catalyst-free, microwave-assisted approach has been developed for the synthesis of 4-azo-butyenolides derivatives by condensing tetronic acid with various anilines. This approach exhibited good functional group compatibility and produced the desired products in good to excellent yields in just 30–40?min. This approach can be seen as a better alternative to protocols with long reaction times used for the synthesis of these compounds, which are synthons for the obtaining of quinolines.