Response of D-, L- and DL-α-alanines to ionizing radiations

There is no statistically significant difference in the response of the enantiomers and the racemate of -alanine to -radiation (⁶⁰Co) and accelerated electrons (10 MeV). The response was measured by the yield of ammonia, one of the separated final products of solid alanine radiolysis and the concentration of free radical CH₃·CH·COO^–, the intermediate product of radiolysis. Some of the properties of the racemate may affect the precision of measurements. The_DL-alanine shows different crystal structure, morphology of crystals, specific density and bulk density than the enantiomers. The response of_L and_DL alanines built into composites may be different because of different reactivity of the enantiomer and the racemate with components during the processing and irradiation.     

Chemical transformations of the condensation products of pyridoxal with L-α-alanine and D-α-alanine

The kinetics and mechanism of the reactions of pyridoxal with L- and D-α-alanine were studied. Under comparable conditions, the condensation of L- and D-α-alanines with pyridoxal includes three kinetically different steps. The first fast step is addition of the amino acid to pyridoxal with formation of the corresponding amino alcohol, the second (slower) step is dehydration of the amino alcohol to give Schiff base, and the third (very slow) step is elimination of α-hydrogen atom from the L-α-amino acid fragment or decarboxylation of the D-α-amino acid fragment, followed by isomerization of the Schiff base to quinoid structure whose subsequent hydrolysis yields pyridoxamine and pyruvic acid or acetaldehyde, respectively. A scheme was proposed for chemical transformations of the pyridoxal condensation products with L- and D-α-alanines.     

Sorption Catalytic Determination of Copper(II) and L-α-alanine on Mg-, Al-Layered Double Hydroxides

Mg-, Al and Mg-, Cu-, Al-layered double hydroxides well-known synthetic hydrotalcite-like sorbents, were used for the first time as carriers for indicators in the sorption catalytic determination of copper(II) and L-α-alanine. Mg-, Al and Mg-, Cu-, Al-layered double hydroxides were synthesized by coprecipitation and characterized using infrared spectroscopy, X-ray diffraction, and scanning electron microscopy. The adsorption of 0.50?mg?L^?1 copper(II) solution by Mg-, Al-layered double hydroxides followed a pseudo-second-order model with an equilibrium sorption capacity of 24.2?×?10^?3?mg?g^?1 (3.8?×?10^?4?mmol g^?1) and a reaction rate constant of 4.2?g mg^?1?min^?1. Mg-, Al-layered double hydroxide tablets were prepared and used for sorption concentration and subsequent sensitive and selective sorption catalytic determination of 5.5?×?10^?3 to 1.0?mg?L^?1 copper(II) at the sorbent phase. The method was used for the analysis of natural water. A method was developed for the determination of α-alanine in Mg-, Cu-, Al-layered double hydroxide tablets with a limit of detection of 4.0?×?10^?3 mol?L^?1. In addition, thin layers of Mg-, Cu-, Al-layered double hydroxide were used to separate α-alanine and determine α-amino acids by thin-layer chromatography.     

酶法拆分D,L-苯丙氨酸制备D-苯丙氨酸

在固定化青霉素酰化酶(IPA-750)存在下,通过N-苯乙酰-D,L-苯丙氨酸(2)的选择性水解完成了酶法拆分D,L-苯丙氨酸(1)制备D-苯丙氨酸(5)的过程。选择性水解的较适宜反应条件为:22.83g,m(2)∶m(IPA-750)=6∶1,pH7.0,于30℃反应5h,产物为N-苯乙酰-D-苯丙氨酸(4)和L-苯丙氨酸(3,收率63%,光学纯度99%)。4用6mol·L-1盐酸于120℃水解反应8h,经脱盐处理得5,收率67%,光学纯度91%。3在含醋酸酐的醋酸溶液中进行消旋化处理,得到100%消旋的1可继续进行下一轮酶法拆分。     

Syntheses,characterizations and SOD-like activities of ternary copper(II) complexes with 1,10-phenanthroline and L- α -amino acids

Three new complexes, [Cu(phen)(L-argH⁺)Cl]Cl?·?2.5H₂O (1), [Cu(phen)(L-leu)(H₂O)]Cl?·2.5H₂O (2) and [Cu(phen)(L-met)(H₂O)]Cl?·?2H₂O (3), where phen?=?1,10-phenanthroline, L-arg?=?L-argininate, L-leu?=?L-leucinate, and L-met?=?L-methioninate, were synthesized and characterized by elemental analysis, molar conductivity, IR and UV-Vis spectroscopies. Complex 1 was structurally characterized by single-crystal X-ray diffraction. The superoxide dismutase (SOD)-like activities of the three complexes were determined by the improved NBT method. The results show that the complexes have high superoxide dismutase-like activities and may act as good mimics for superoxide dismutases.     

Total synthesis of (±)-maistemonine, (±)-stemonamide, and (±)-isomaistemonine

A full account of the total synthesis of (±)-maistemonine, (±)-stemonamide, and (±)-isomaistemonine is presented. Two approaches have been developed to construct the basic pyrrolo[1,2-a]azepine core of the Stemona alkaloids, featuring a tandem semipinacol/Schmidt rearrangement of a secondary azide and a highly stereoselectively desymmetrizing intramolecular Schmidt reaction, respectively. To build the common spiro-γ-butyrolactone, a new protocol was carried out by utilizing an intramolecular ketone-ester condensation as the key transformation. The vicinal butyrolactone moiety of (±)-maistemonine was stereoselectively introduced via a one-pot procedure involving the epimerization at C-3 and carbonyl allylation/lactonization. Moreover, (±)-stemonamide was divergently synthesized from a common intermediate, and (±)-isomaistemonine was obtained via the epimerization of (±)-maistemonine at C-12.     

Facile Syntheses of (±)-Curcuphenol, (±)-Curcudiol, (±)-Curcuhydroquinone,and (±)-Curcuquinone

The syntheses of (±)-curcuphenol 1, (±)-curcudiol 2, (±)-curcuhydroquinone 3, and (±)-curcuquinone 4 have been achieved. The key steps involved in the syntheses were the Reformatsky reaction and hydrogenation reaction.     

Spectroscopic,electrocatalytic, and photoelectrochemical characteristics of mixed-ligand bis(β-dicarbonylato) phthalocyanine complexes of zirconium(IV) and hafnium(IV)

The electronic absorption (EAS) and fluorescence spectra and electrocatalytic and photoelectrochemical characteristics of mixed-ligand complexes of zirconium(IV) and hafnium(IV) based on phthalocyanines in solutions and in thin films were investigated. It was established that a significant bathochromic shift of the Q band and redistribution of the intensities in the absorption bands are observed in the electronic absorption spectra. It was shown that films of the synthesized compounds are promising for use as photosensitizers and electrochemical sensors for oxygen in solution. __________ Translated from Teoreticheskaya i éksperimental’naya Khimiya, Vol. 44, No. 3, pp. 133–137, May–June, 2008.     

Complexes of Cu(I) and Pd(II) with (+)-camphor and (–)-cavrone thiosemicarbazones: Synthesis,structure, and cytotoxicity of the Pd(II) complex

CuLCl, CuL¹Cl, PdLCl₂, and PdL¹Cl₂ complexes [L and L¹ being (+)-camphor and (–)-carvone thiosemicarbazones, respectively] have been synthesized. The structure of binuclear [Pd₂L²²Cl₄] complex has been determined by means of X-ray diffraction. The L² ligand (dehydrogenated (–)-carvone thiosemicarbazone) is coordinated via the bridging S atom to two Pd atoms. The complexes of Cu(I) and Pd(II) presumably have polynuclear and binuclear structure, respectively. These facts are in good agreement with IR and NMR spectroscopy as well as mass spectrometry data which indicate the coordination of L and L¹ ligands via the S atom. The influence of L¹ and PdL¹Cl₂ on viability of the Hep2 cell line has been studied. The PdL¹Cl₂ complex is more cytotoxic than L¹ ligand.     

Isolation,purification, and characterization of cyclomaltodecaose (ε-CD)

-Cyclodextrin (-CD) is a cyclic oligosaccharide, composed of ten -1,4-linked D-glucoses reported by Frenchet al. in 1965¹⁾, but has not been studied because of the difficulty in the preparation and purification of large-ring CDs composed of more than nine -1,4-linked D-glucose units. This report describes the purification and characterization of -CD. Furthermore, the crystal and molecular structure of -CD hydrate -CD 19H₂O) was elucidated by X-ray analysis.     

Preparation and polymerization mechanism of dihydroxy-capped PCL,poly(CL-b-PEG-b-CL) and poly(DTC-b-CL-b-DTC)

PCL possesses a wide range of medical applications, such as tissue engineering and controlled drug release, because of its good biodegradability and miscibility. In order to extend the use of PCL, researchers have been exploring its structural and chemica…     

Synthesis,spectral, magnetic,electrochemical and catalytic studies of cyclam-based copper(II) and nickel(II) complexes–effect of N-substitution

New N-substituted cyclam ligands 1,8-[bis(3-formyl-2-hydroxy-5-methyl)benzyl]-1,4,8,11-tetraazacyclotetradecane, 1,8-[bis(3-formyl-2-hydroxy-5-methyl)benzyl]-4,11-dimethyl-1,4,8,11-tetraazacyclotetradecane, 1,8-[bis(3-formyl-2-hydroxy-5-bromo)benzyl]-1,4,8,11-tetraazacyclotetradecane, and 1,8-[bis(3-formyl-2-hydroxy-5-bromo)benzyl]-4,11-dimethyl-1,4,8,11-tetraazacyclotetradecane (L¹–L⁴) were synthesized and mononuclear copper(II) and nickel(II) complexes prepared. The ligands and complexes were characterized by elemental analysis, electronic, IR, ¹H NMR and ¹³C NMR spectral studies. N-alkylation causes red shifts in the λ_max values of the complexes. Copper(II) complexes show one-electron, quasi-reversible reduction waves in the range ?1.04 to ?1.00 V. The nickel(II) complexes show one-electron, quasi-reversible reduction waves in the range ?1.18 to ?1.30 V and one-electron, quasi-reversible oxidation waves in the range +1.20 to +1.40 V. The reduction potential of the copper(II) and nickel(II) complexes of the ligands L¹ to L² and L³ to L⁴ shift anodically on N-alkylation. The ESR spectra of the mononuclear copper(II) complexes show four lines, characteristic of square-planar geometry with nuclear hyperfine spin 3/2. All copper(II) complexes show a normal room temperature magnetic moment value μ_eff?=?1.70–1.74 BM which is close to the spin only value of 1.73 BM. Kinetic studies on the oxidation of pyrocatechol to o-quinone using the copper(II) complexes as catalysts and on the hydrolysis of 4-nitrophenylphosphate using the copper(II) and nickel(II) complexes as catalyst were carried out. The tetra-N-substituted complexes have higher rate constants than the corresponding disubstituted complexes.     

Kinetics and mechanism of the anation of (αβ)-hydroxo(tetraethylenepentamine)cobalt(III) by thiosulfate, the base hydrolysis of the (sulfur-bonded) thiosulfato(tetraethylenepentamine)-cobalt(III) and photochemistry of oxygen and sulfur-bonded thiosulfato complexes

Summary The reaction of ()-(tetren)CoOH²⁺ with S₂O ₃ ^2- in the 7.25–8.28 pH range at 20–40 °C yielded S- (yellow) and O- (purple) bonded thiosulfato(tetren)cobalt(III) complexes, the former in larger quantities. The rate determining step is preceded by diffusion-controlled ion-pair [(tetren)CoOH²⁺,S₂O ₃ ^2- ] formation. Replacement of coordinated OH^- by S₂O ₃ ^2- is interpreted in terms of an internal conjugate base mechanism: (tetren)CoOH²⁺ (tetren-H)CoOH ₂ ²⁺ , the reactive amido conjugate base being generated by intramolecular proton transfer from the coordinated NH site.In acid medium the S-bonded (tetren)Co(S₂O₃)⁺ is highly stable to redox decomposition, in contrast to its pentaammine analogue. The complex however, undergoes base hydrolysis yielding the corresponding hydroxo complex. The rate and activation parameters for the base hydrolysis have been reported. Photolysis of O- and S-bonded isomers of [(tetren)CoS₂O₃]⁺ in acidic medium at 254 and 313 nm, respectively, yielded aquation products accompanied by some decomposition of S₂O ₃ ^2- .     

A new and convenient synthesis of protoberberine alkaloids: (±)-tetrahydropalmatine, (±)-sinactine, (±)-canadine,and (+)-stylopine

2,3,9,10-Tetraoxygenated protoberberine alkaloids (14) were efficiently synthesized from the readily available benzaldehyde (2 or 10) via the benzylphenethylamines (11) and 2-phenethylisoquinolin-3-ones (12 and 13).     

Syntheses,Crystal Structures and Antibacterial Activities of Schiff Base of Nickel(Ⅱ) and Copper(Ⅱ) Complexes

A new kind of Schiff base HL(HL= 1-phenyl-3-methyl-4-(p-methylbenzoyl)-5-pyrazolone with L-Leucine methyl ester) and complexes Ni L′_2·0.75C_2H_5OH·0.25H_2O,Cu L′′2(L′ = 1-phenyl-3-methyl-4-(p-methylbenzoyl)-5-pyrazolone with L-leucine ethyl,L′′ = 1-phenyl-3-methyl-4-(p-methylbenzoyl)-5-pyrazolone with L-leucine) have been synthesized and structurally determined by X-ray diffraction. For HL: crystal structure determination indicates that there are two independent HLs with different conformations in one asymmetric unit. For complex 1: the Ni(Ⅱ) ion is six-coordinated by two carbonyl oxygen atoms from pyrazolone ring,two nitrogen atoms from different HL′ and two oxygen atoms from L-Leucine ethyl ester to form a distorted octahedral geometry. For complex 2: the Cu(Ⅱ) ion is four-coordinated by one carbonyl oxygen atom from the pyrazolone ring,one nitrogen atom from HL′′,and two different carboxylic oxygen atoms from L-leucine with the same conformation to form a distorted quadrilateral geometry.     

Synthesis,structure and reactions of μ-oxobis(arenesulfonatotriarylbismuth)

Hydrolysis of triarylbismuth bis(arenesulfonates) in acetone gives bismuth derivatives of the general formula [Ar₃Bi(OSO₂Ar)]₂O (Ar = Ph, p-Tol; Ar = Ph, C₆H₄Me-4, C₆H₃Me₂-2,4, C₆H₃Me₂-3,4). The structure of -oxobis[(3,4-dimethylbenzenesulfonato)triphenylbismuth] was established by means of X-ray diffraction. The molecule has a linear centrosymmetric structure with the bridging oxygen atom in the inversion center. The bismuth atom has a distorted trigonal bipyramidal coordination with the bridging oxygen atom and the arenesulfonate group in axial positions. The Bi-C and Bi-O_term distances are 2.200(2), 2.204(3), and 2.442(2) Å, and the Bi-O_br distances are 2.067(1) Å.Translated from Zhurnal Obshchei Khimii, Vol. 74, No. 9, 2004, pp. 1466–1471.Original Russian Text Copyright © 2004 by Sharutin, Egorova, Sharutina, Ivanenko, Pavlushkina, Gerasimenko, Pushilin.This revised version was published online in April 2005 with a corrected cover date.     

α-Amino 1,3-dithioketal mediated asymmetric synthesis of piperidines (L-733,060) and tetrahydrofuran glycines

Sulfinimine-derived α-amino 1,3-dithianes and α-amino carbonyl chiral building blocks, are utilized in asymmetric syntheses of (+)-(tetrahydrofuran-2-yl)glycine and the 2,3-disubstituted piperidine (+)-L-733,060.