L-α-Aminoadipic Acid from L-Glutamic Acid

A convenient procedure for the preparation of L-α-aminoadipic acid from L-glutamic acid is described.     

2-Hydroxyphenylphosphinic Acid: P-Analogue of Salicylic Acid?

Abstract

Substitution of the carboxyl group -C(O)OH by -P(O)(OH)₂ and -P(O)R(OH) leads to compounds of interest to agriculture, technics and pharmacology. Under these aspects the P-analogon 1 of salicylic acid was prepared, because the monobasic -P(O)H(OH) group resembles more the carboxyl function than the dibasic moiety -P(O)(OH)₂.     

An Efficient Procedure for Esterification of Aryloxyacetic Acid and Arylthioacetic Acid Catalyzed by Silica Sulfuric Acid

Aryloxyacetate and arylthioacetate are wildly used in herbicides, plant regulator and insecticides. Recently, Wille et al. have reported that methyl aryloxyacetate is an efficient agent to prevent and treat allergic contact dermatitis.[1] The most popular synthesis is by heating sodium phenoxide (mercaptide) with ethyl chloroacetate in DMF,[2] or by the esterification of acid with alcohol using concentrated H2SO4 as catalyst.[3] In this paper, synthesis of aryloxyacetate and aryl thioacetate from aryloxyacetic acid and arylthioacetic acid respectively in ether catalyzed by silica sulfuric acid in 83%～94% yields is described. The catalyst is reused for 3 times without significant loss of activity (Entry 4). Compared with common procedures, the present procedure possesses the advantages of the operational simplicity, short reaction time,less-corrosion, high yield and reusable catalyst.     

Propanephosphonic Acid Anhydride–Mediated Cyclodehydration of Maleic Acid Monoamides

Propanephosphonic acid anhydride (T3P) has been proposed as a novel reagent for the preparation of maleic acid isoimides from the corresponding monoamides. A series of substituted aromatic and aliphatic isoimides have been prepared in good yields. The main advantage of this synthetic method is the use of environmentally benign, cost-efficient reagents and solvents, which are also safer to handle than the ones employed previously.

Supplemental materials are available for this article. Go to the publisher's online edition of Synthetic Communications® to view the free supplemental file.     

Effect of Acetic Acid on Citric Acid Fermentation in an Integrated Citric Acid–Methane Fermentation Process

An integrated citric acid–methane fermentation process was proposed to solve the problem of extraction wastewater in citric acid fermentation process. Extraction wastewater was treated by anaerobic digestion and then recycled for the next batch of citric acid fermentation to eliminate wastewater discharge and reduce water resource consumption. Acetic acid as an intermediate product of methane fermentation was present in anaerobic digestion effluent. In this study, the effect of acetic acid on citric acid fermentation was investigated and results showed that lower concentration of acetic acid could promote Aspergillus niger growth and citric acid production. 5-Cyano-2,3-ditolyl tetrazolium chloride (CTC) staining was used to quantify the activity of A. niger cells, and the results suggested that when acetic acid concentration was above 8 mM at initial pH 4.5, the morphology of A. niger became uneven and the part of the cells’ activity was significantly reduced, thereby resulting in deceasing of citric acid production. Effects of acetic acid on citric acid fermentation, as influenced by initial pH and cell number in inocula, were also examined. The result indicated that inhibition by acetic acid increased as initial pH declined and was rarely influenced by cell number in inocula.     

Improved One-pot Synthesis of 4,6-Dihydroxyisophthalic Acid and 2,3-Dihydroxyterephthalic Acid

An improved method for the large-scale preparation of 4,6-dihydroxyisophthalic acid and 2,3-dihydroxyterephthalic acid has been developed.Compared to the previous procedures,this new process-requires much lower CO2 pressure of 0.3 Mpa and shorter reaction time.thus providing a convenient access for large-scale synthesis.The yield is high （93% and 65%,respectively）, and the oxidation of phenol is nearly inhibited,neither decolorization nor further chromatographic purification is required.     

Crystal Structure of Nicotinic Acid·3,5-dinitrobenzoic Acid Organic Adduct

1INTRODUCTIONThedevelopmentofhighlyefficientnonlinearoptical(NLO)crystalsforvisibleandultraviolet(UV)regionsisextremelyimportantforbothlaserspectroscopyandlaserprocessing.Themainmeritsoforganicmaterialscomparedwithinorganiconesforsuchsecond-harmonicgenera…     

Esterification of Glycerol by Oleic Acid and Selective Hydrogenation of Oleic Acid Methylester Over Acid and Ru-Sn-B Supported Mesoporous AlMCM-41

Demand for large pore size molecular sieves has given rise to great interests in a new family of silica-based mesoporous materials designated as M41s, which expand typical molecular sieves into an extra-large pore range and generate the potential for the applications of these materials in catalysis and sorption for very bulky molecules1-6. MCM-41 possesses a hexagonal arrangement of uniform mesopore ranging from 15 to 100 ? and can be prepared with varied Si/Al ratios. The investigations of …     

Self-assembled Monolayers of n-Hexadecanoic Acid and α-Hydroxyl n-Hexadecanoic Acid on Titanium Surfaces

Ｄｕｒｉｎｇｔｈｅｌａｓｔｔｗｏｄｅｃａｄｅｓ ,ｐｅｏｐｌｅｈａｖｅｐａｉｄｍｕｃｈｉｎｔｅｒｅｓｔｉｎｔｈｅｃｈｅｍｉｓｔｒｙｏｆｓｅｌｆ ａｓｓｅｍｂｌｅｄｍｏｎｏｌａｙｅｒｓ(ＳＡＭｓ) ,ｗｈｉｃｈｓｈｏｗｓｐｏｗｅｒｆｕｌａｐｐｌｉｃａｔｉｏｎｓｉｎｔｈｅｆｉｅｌｄｓｏｆｂｉｏｓｅｎｓｏｒｓａｎｄｔａｉｌｏｒｅｄｓｕｒｆａｃｅｓ .Ｐａｒｔｉｃｕｌａｒｌｙ ,ｔｗｏｔｙｐｅｓｏｆＳＡＭｓ ,ｉ.ｅ .,ｔｈｉｏｌｓ/ｔｈｉｏｌａｔｅｓｏｎｇｏｌｄａｎｄｓｉｌａｎｅｓｏｎｓｉｌｉｃｅｏｕｓｓｕｒｆａｃｅ…     

Acid–Base Behavior in Supercritical Water: β-Naphthoic Acid–Ammonia Equilibrium

Equilibrium constants for the reaction of -naphthoic acid and ammonia, K _BHA, were measured with UV-vis spectroscopy in water from 25°C to 400°C. At high density K _BHA decreases with temperature, the normal behavior for an exothermic reaction of a stronger acid and base to a weaker acid and base. At low density, the reaction becomes endothermic as the solvation of the ionic products becomes weaker. These data were combined with literature results for the dissociation of water and ammonia to determine equilibrium constants for the dissociation of -naphthoic acid and the reaction of -naphthoic acid and OH^- Whereas the density (and dielectric constant) of water have only a modest effect on the isocoulombic reaction of -naphthoic acid and OH^-, they have a large effect on all of the other reactions which are ionogenic.     

Primary Amine‐Initiated Polymerizations of α–Amino Acid N‐Thiocarbonic Acid Anhydrosulfide

The N‐thiocarbonic acid anhydrosulfides NTAs of D,L‐leucine, D,L‐phenylalanine and sarcosine were polymerized in dioxane by addition of n‐hexylamine as initiator. Despite variation of the monomer‐initiator ratio (M/I) only low yields of oligopeptides were obtained from D,L‐Leu‐ and D,L‐Phe‐NTA. Both yields and molecular weights were almost twice as high for polymerizations of Sar‐NTA. MALDI‐TOF mass spectra confirmed that the isolated oligo‐and polypeptides possess the expected structure with one reactive amino end group. Therefore, it is surprising that the polymerizations stopped at low conversions. Two hypotheses explaining this phenomenon are discussed.     

Dielectric Relaxation of the β-Cyclodextrin Complexes with Tridecanoic Acid and 1,13-Tridecanedioic Acid

The frequency and temperature dependence of the real (') and imaginary (') parts of the dielectric permittivity of the polycrystalline complex-cyclodextrin-tridecanoic acid in two hydration forms (with 16.2 and 10.7 water molecules) and -cyclodextrin-1,13-tridecanedioic acid with 16.4 and 10.5 water molecules have been investigated, in the frequency range 0.1–100 kHz and temperature range 120–310 K. The dielectric behavior is described well by Debye-type relaxation dispersion. All systems except for the complex of partially dehydrated monocarboxylic acid, exhibit an additional -dispersion, at low frequencies (f < 1000 Hz). Only one-step was found in the ' vs. Tplots of both complexes in the two hydration forms, a fact indicating that the watermolecules cannot be divided into strongly bound and easily movable molecules. The'vs. T plots, at a fixed frequency (200 Hz), show the characteristic peakattributed to a transition between ordered and disordered -CD hydroxyl groupsand water molecules. The transition temperature was 202.7 K for all systems examinedexcept for the complex -CD-tridecanoic acid.16.2 H₂O (214.5 K). This means that the order to disorder transformation process was unaffected by the dehydration process in the case of the dicarboxylic acid complex, whereas in the case of the monocarboxylic acid, it was unexpectedly facilitated. The relaxation time varies with temperature, in a like curve (in the range 8–14 s), with maximum values located at the corresponding order-disorder transition temperatures. The activation energies of the fully hydrated complexes have absolute values of 5 kJ/mol in the range 1.98–3.82 K_{BT transition} which are higher than the corresponding values of :2 kJ/mol of the dehydrated complexes. A thermal hysteresis observed in all complexes is a result of the order-disorder transformation.     

Coulometric Titration of Thiocyanate,Mercaptoacetic Acid,and β-Mercaptopropionic Acid with Electrogenerated Hypobromite

Abstract

Several sulfur containing ligands have been determined by coulometric titration using biamperometric end point detection. Satisfactory results were obtained for the direct determination of thiocyanate, mercaptoacetic acid and β-mercaptopropionic acid. Silver has been determined by an indirect method involving the determination of excess precipitant.     

Synthesis and Molecular Recognition of Novel Cyclic Pseudopeptides Containing L-Glutamic Acid or L-Aspartic Acid Backbones

Novel cyclic pseudopeptides containing L-glutamic acid or L-aspartic acid backbone structures were efficiently synthesized and characterized. Their chiral recognition properties for L- and D-amino acid methyl ester hydrochloride were discussed also.     

Monitoring Homovanillic Acid and Vanillylmandelic Acid in Human Urine by Capillary Electrophoresis with Electrochemical Detection

A simple,rapid and low-cost method of separation and determination of homovanillic acid and vanillylmandelic acid in human urine was developed based on capillary zone electrophoresis/amperometric detection with high sensitivity and good resolution.     

A Light Active Barbituric Acid Der

A　Light　Active　Barbituric　Acid　Der...     

Recognition of α-Amino Acid from β- and γ-Amino Acid by N -Phosphorylation

The reactivity of N -phosphoryl f -alanine differs from N -phosphoryl g -alanine and N -phosphoryl n -amino butyric acid enormously. N -phospho- f -alanine could self-activate to yield N -phosphopeptides either in aqueous or nonaqueous media, but not g - or n -amino acid analogues. The mechanism of the reaction is discussed.     

Chlorogenic Acid UVA–UVB Photostability

Chlorogenic acid is a natural potent antioxidant. It can be used in cosmetics formulations, but for this purpose its photochemical stability should be determined to ensure that the compound will not be degraded after UV radiation exposure. To evaluate this possibility, the concentration of a chlorogenic acid solution was determined by HPLC before and after UVA and UVB irradiation. The results indicate that chlorogenic acid is not degraded under UVA or UVB irradiation.     

Synthesis of β–Amino Acid Derivatives

In recent years, β-amino acids and their derivatives have attracted considerable attention due to their occurrence in biologically active natural products, such as dolastatins, cyclohexylnorstatine and Taxol. β–Amino acids also find application in the synthesis of β–lactams, piperidines, indolizidines. Moreover, the peptides consisting of β–amino acids, the so-called β–peptides, have been extensively studied recently. Consequently, considerable efforts have been directed to the synthe…     

Preparation and Characterization of Molybdotungstoniobogermanic Acid

Recently,thepreparationandpropertiesofheteropolycomplexeshaveincreasinglyattractedattentioninvariousfieldsofchendstIy,especiallyincatalysicapplicationsfortheiruniqueproperties'.Sincel988,thestudiesoffour-baseheteropolycomplexeswiththeKegginstructurehavebeenreported.Asthespecialbifunctionalcatalyticand.-lantisepsispropertyoftheheteropolycomplexescontainingniobium',andsofarthemolybdotungstoniobogermanicheteropolycomplexesinwhichthecentralatomisgermanium,havenotbeenreportedyet,ennea-tungsto-bi-mo…