Characterization of archaeological frankincense by gas chromatography-mass spectrometry

A simple gas chromatography-mass spectrometry (GC-MS) method has been developed for the characterization of frankincense in archaeological samples. After trimethylsilylation of the methanolic extract, 15 triterpenoids have been found among the chemical constituents of commercial olibanum (alpha-boswellic acid, 3-O-acetyl-alpha-boswellic acid, beta-boswellic acid, 3-O-acetyl-beta-boswellic acid, alpha-amyrin, beta-amyrin, lupeol, 3-epi-beta-amyrin, 3-epi-beta-amyrin, 3-epi-lupeol, alpha-amyrenone, beta-amyrenone, lupenone, 3alpha-hydroxy-lup-20(29)-en-24-oic acid and 3-O-acetyl-hydroxy-lup-20(29)-en-24-oic acid). These compounds have been unequivocally identified by retention time and mass spectral comparison with pure standards previously isolated, for the most part, in our laboratory. Within these triterpenes, acid ones, the corresponding O-acetates, and their products of degradation were found to be characteristic of frankincense (Boswellia resin). The presence of these unusual triterpenic compounds in an archaeological resinous sample, recovered during excavations from Dahshour site (Egypt, XIIth Dynasty), enabled us to identify unambiguously frankincense resin among several other materials. Additional chromatographic peaks of this sample were assigned to broad chemical classes using retention time and mass spectra features.     

Chiral Recognition in π Complexes of Alkenes,Aldehydes, and Ketones with Transition Metal Lewis Acids; Development of a General Model for Enantioface Binding Selectivities

Prochiral alkenes, aldehydes, and ketones constitute the most frequently used starting materials for enantioselective organic syntheses. Protocols often involve chiral binding agents or Lewis acids that can give two diastereomeric adducts, the ratios of which are measures of chiral recognition. With π adducts, the diastereomers differ in the enantioface of the C?C or O?C group bound to the Lewis acid. This review provides the first comprehensive analysis of such equilibria and related binding phenomena with chiral transition metal Lewis acids. An extensive body of data from the authors' laboratory for complexes of the pyramidal rhenium fragment [(η⁵?C₅H₅)Re(No)(PPh₃)]⁺ ( I ) affords particular insight. Literature data for other complexes are also summarized. A general model for chiral recognition based upon the relative steric properties of four quadrants is presented. This enables binding selectivities to be individually and rationally optimized for different classes of ligands. Electronic effects are also identified and correlated with specific structural properties. Relationships between binding equilibria, reactivity, and product configurations are discussed.     

Complexation of Some Amino Acids and Peptides by p-Sulfonatocalix[4]arene and Hexasodium p-Sulfonatocalix[6]arene in Aqueous Solution

The stability constants (log K), the reaction enthalpy( H) and entropy ( S) of the complexesformed between some amino acids (glycine, L-alanine,L-valine, L-leucine, L-phenylalanine, L-tryptophan,L-threonine, and L-lysine) and peptides (glycyl-glycine,glycyl-L-alanine, glycyl-L-leucine, glycyl-L-phenylalanine,L-leucyl-glycine, L-leucyl-L-alanine, glycyl-L-valine,L-leucyl-glycyl-glycine, and glycyl-glycyl-glycine) withp-sulfonatocalix[4]arene and hexasodiump-sulfonatocalix[6]arene in aqueous solutions by meansof calorimetric titration have been investigated. The reportedresults demonstrate that the amino acids and peptides under studyform complexes with both p-sulfonatocalix[4]areneand hexasodium p-sulfonatocalix[6]arene. In the case of theamino acids and peptides the complexation with water-solublecalixarenes in aqueous solution is favored by enthalpiccontributions and disfavored by entropic contributions. However,no influence of the ring size of the calixarenes upon thecomplexation is observed. By comparison with the reaction ofthe sodium salt of phenol-4-sulfonic acid with amino acids amacrocyclic effect in case of the calixarenes is possible.     

Synthesis and Crystal Structure of a Novel Layered Lead(Ⅱ) Carboxylate-sulfonate Compound Templated by 4,4''-Bipyridine

A new lead(Ⅱ) carboxylate-sulfonate has been hydrothermally synthesized and characterized by X-ray single-crystal and elemental analyses. It crystallizes in triclinic, space group P,(1) with a=8.1573(6), b=9.4663(7), c=12.7488(9) (A), α=89.2320(10), β=80.7380(10), γ=77.9760(10)°, Z=2, V=950.10(12) (A)3, Mr=599.57, Dc=2.096 g/cm3, μ=9.032 mm-1, F(000)=572, the final R=0.0412 and wR=0.1035. It has a 1D chain structure, and the Pb(Ⅱ) is six-coordinated. Two PbO6 polyhedra are interconnected via edge-sharing into a two-core unit. Such units are further interconnected by 3-sulfonato-benzoic acids into 1D chains which are linked by hydrogen bonds into a layer structure. The 4,4'-bipyridines are located at the interlayer space and link the layers into a supramolecular structure by π-π stacking interactions.     

Solubility of α-amino acids in water under high pressure: glycine, -alanine, -valine, -leucine, and -isoleucine

The solubility of glycine, -alanine, -valine, -leucine, and -isoleucine in water was measured at 298.15 K and pressures up to 400 MPa. The standard deviation of the logarithm of the solubility is 0.001–0.003, equal to or better than the accuracy of atmospheric pressure measurement in the literature (0.001–0.05). A variety of solubility phenomena were observed. The solubility of glycine decreased with increasing pressure, whereas that of -alanine increased. The -valine and -isoleucine have a solubility maximum at around 100 MPa, and -leucine seems to exhibit a solid-phase phase transition at around 200 MPa. Pressure coefficient of the solubilities at 0.10 MPa is compared with that thermodynamically estimated in reference to aqueous density measurements of glycine and -alanine at 298.15 K and 0.10 MPa, supporting a reliability of our high-pressure measurements.     

THERMODYNAMIC STUDY ON ADSORPTION OF AROMATIC SULFONIC ACIDS ONTO MACROPOROUS WEAK BASE ANION EXCHANGER FROM AQUEOUS SOLUTIONS

 The adsorption equilibrium isotherms of three aromatic sulfonic acid compounds, 2-naphthalenesulfonic acid, p-toluenesulfonic acid and p-chlorobenzenesulfonic acid, from aqueous solutions by macroporous weak base anion exchanger within the temperature range of 293 K-313 K were obtained. Several isotherm equations were correlated with the equilibrium data, and the experimental data was found to fit the three-parameter Redlich-Peterson equation best within the entire range of concentrations. The study showed that the hydrophobicity of solute has distinct influence on adsorption capacity of the anion exchanger for the aromatic sulfonic acid. Moreover, estimations of the isosteric enthalpy, free energy,and entropy change of adsorption were also reported. The positive isosteric enthalpy and entropy change for adsorption indicate an endothermic and entropy driven process in the present study.     

Solvothermal Synthesis, Crystal Structure and Electrochemical Property of Complex [Co(p-MBA)2(2,2''-bipy)(H2O)]·(H2O)

One novel complex [Co(p-MBA)2(2,2'-bipy)(H2O)]·(H2O) has been synthesized by the reaction of p-methylbenzoic acid with 2,2'-bipyridine in the solvent mixture of water and methanol. It crystallizes in triclinic, space group P-1 with a=0.70479(14), b=1.1211(2), c=1.6718(3) nm, α=103.806(3), β=90.795(3), γ=104.207(3)°, V=1.2399(4) nm3, Mr=512.41, Dc=1.373 g/cm3, Z=2, F(000)=532, μ=0.733 mm-1, R=0.0432 and wR=0.0957. The crystal structural analysis shows that the cobalt atom is coordinated with three oxygen atoms from two p-methylbenzoic acids and one water molecule and two nitrogen atoms from one 2,2'-bipyridine,forming a distorted square-pyramidal coordination geometry. The cyclic voltammetry behavior of the complex is also reported.     

AQC柱前衍生反相高效液相色谱法测定土壤中氨基酸

以2-氨基丁酸为内标物,6-氨基喹啉基-N-羟基琥珀酰亚氨基甲酸酯(AQC)为柱前衍生试剂,用XTerraC18柱,1.8mmol/L甲酸铵溶液(pH=3.0)和乙腈为流动相,采用梯度洗脱,光电二极管(PDA)检测器在248nm波长处检测,建立了一种利用反相高效液相色谱同时测定土壤中17种氨基酸的分析方法。方法重现性好,精密度高,氨基酸浓度在25~600μmol/L范围内,线性相关系数均大于0.99;各氨基酸检出限≤0.5pmol。并且在该色谱条件下,获得了灵敏度较高,彼此分离良好的17种AQC衍生氨基酸的LC-MS质谱总离子流图,为今后土壤氨基酸的深入研究提供了更加有利的手段。     

Surface effects on phase transition behavior and thermal polymerization of long-chain diynoic acids in micro DSC measurements

Effects of metal surfaces, such as aluminium, silver and gold, on the melting behavior and thermal polymerization of long-chain diynoic acids having a diacetylene group at different positions were investigated by thermal analyses using DSC, TG and other methods. The surface effects of metals were significant in the order of Ag, Al and Au. These effects are attributable to the anchoring of carboxyl group on the surface by chemisorption, which leads to unfavorable condition for polymerization of heptadeca-2,4-diynoic acid. In the case of tricosa-10,12-diynoic acid, containing a flexible methylene chain, inserted between COOH and C≡C?C≡C groups, the anchoring of COOH on the metal surface causes rather favorable effect on the polymerization.     

Mechanochemical Preparation of Water-Soluble Forms of Triterpene Acids

A waste-free technology for mechanochemical processing of fir needles into a biologically active preparation that regulates plant growth was developed. A preparation exhibiting cytokinin activity due to the presence in it of water-soluble forms of triterpene acids can be prepared using the proposed method. The effectiveness of the proposed method was confirmed by instrumental methods and biological tests.