bluuebunny/crossref_metadata_2025 huggingface dataset:
Salt Stress inDesulfovibrio vulgarisHildenborough: an Integrated Genomics Approach
Authors: Mukhopadhyay Aindrila , He Zhili , Alm Eric J. , Arkin Adam P. , Baidoo Edward E. , Borglin Sharon C. , Chen Wenqiong , Hazen Terry C. , He Qiang , Holman Hoi-Ying , Huang Katherine , Huang Rick , Joyner Dominique C. , Katz Natalie , Keller Martin , Oeller Paul , Redding Alyssa , Sun Jun , Wall Judy , Wei Jing , Yang Zamin , Yen Huei-Che , Zhou Jizhong , Keasling Jay D.
Published: May 2006

The ability ofDesulfovibrio vulgarisHildenborough to reduce, and therefore contain, toxic and radioactive metal waste has made all factors that affect the physiology of this organism of great interest. Increased salinity is an important and frequent fluctuation faced byD. vulgarisin its natural habitat. In liquid culture, exposure to excess salt resulted in striking elongation ofD. vulgariscells. Using data from transcriptomics, proteomics, metabolite assays, phospholipid fatty acid profiling, and electron microscopy, we used a systems approach to explore the effects of excess NaCl onD. vulgaris. In this study we demonstrated that import of osmoprotectants, such as glycine betaine and ectoine, is the primary mechanism used byD. vulgaristo counter hyperionic stress. Several efflux systems were also highly up-regulated, as was the ATP synthesis pathway. Increases in the levels of both RNA and DNA helicases suggested that salt stress affected the stability of nucleic acid base pairing. An overall increase in the level of branched fatty acids indicated that there were changes in cell wall fluidity. The immediate response to salt stress included up-regulation of chemotaxis genes, although flagellar biosynthesis was down-regulated. Other down-regulated systems included lactate uptake permeases and ABC transport systems. The results of an extensive NaCl stress analysis were compared with microarray data from a KCl stress analysis, and unlike many other bacteria,D. vulgarisresponded similarly to the two stresses. Integration of data from multiple methods allowed us to develop a conceptual model for the salt stress response inD. vulgaristhat can be compared to those in other microorganisms.
Xanthosine Utilization in
Salmonella enterica
Serovar Typhimurium Is Recovered by a Single Aspartate-to-Glycine Substitution in Xanthosine Phosphorylase
Authors: Riis Hansen Michael , Tranekjær Jørgensen Jesper , Dandanell Gert
Published: May 2006

xapABR
from
Salmonella enterica
was analyzed and compared with the corresponding
Escherichia coli
genes.
xapB
and
xapR
, but not
xapA
, encode functional proteins. An
S. enterica
XapA(Asp72Gly) mutant that restores the phosphorolytic activity was selected. The purified mutant enzyme has different kinetic constants than the
E. coli
enzyme but similar substrate specificity.
Subcellular Partitioning of Transcription Factors inBacillus subtilis
Authors: Doherty Geoff P. , Meredith Donna H. , Lewis Peter J.
Published: May 2006

RNA polymerase (RNAP) requires the interaction of various transcription elongation factors to efficiently transcribe RNA. During transcription of rRNA operons, RNAP forms highly processive antitermination complexes by interacting with NusA, NusB, NusG, NusE, and possibly several unidentified factors to increase elongation rates to around twice those observed for mRNA. In previous work we used cytological assays withBacillus subtilisto identify the major sites of rRNA synthesis within the cell, which are called transcription foci. Using this cytological assay, in conjunction with both quantitative native polyacrylamide gel electrophoresis and Western blotting, we investigated the total protein levels and the ratios of NusB and NusG to RNAP in both antitermination and mRNA transcription complexes. We determined that the ratio of RNAP to NusG was 1:1 in both antitermination and mRNA transcription complexes, suggesting that NusG plays important regulatory roles in both complexes. A ratio of NusB to RNAP of 1:1 was calculated for antitermination complexes with just a 0.3:1 ratio in mRNA complexes, suggesting that NusB is restricted to antitermination complexes. We also investigated the cellular abundance and subcellular localization of transcription restart factor GreA. We found no evidence which suggests that GreA is involved in antitermination complex formation and that it has a cellular abundance which is around twice that of RNAP. Surprisingly, we found that the vast majority of GreA is associated with RNAP, suggesting that there is more than one binding site for GreA on RNAP. These results indicate that transcription elongation complexes are highly dynamic and are differentially segregated within the nucleoid according to their functions.
The Periplasmic Folding of a Cysteineless Autotransporter Passenger Domain Interferes with Its Outer Membrane Translocation
Authors: Rutherford Nancy , Charbonneau Marie-Ève , Berthiaume Frédéric , Betton Jean-Michel , Mourez Michael
Published: May 2006

Autotransporters are single polypeptides consisting of an outer membrane translocation domain mediating the translocation of a passenger domain. The periplasmic folding state of the passenger domain is controversial. By comparisons of passenger domains differing in their folding properties, our results suggest that periplasmic folding of passenger domains interferes with translocation.
Escherichia coli
Competence Gene Homologs Are Essential for Competitive Fitness and the Use of DNA as a Nutrient
Authors: Palchevskiy Vyacheslav , Finkel Steven E.
Published: May 2006

Natural genetic competence is the ability of cells to take up extracellular DNA and is an important mechanism for horizontal gene transfer. Another potential benefit of natural competence is that exogenous DNA can serve as a nutrient source for starving bacteria because the ability to “eat” DNA is necessary for competitive survival in environments containing limited nutrients. We show here that eight
Escherichia coli
genes, identified as homologs of
com
genes in
Haemophilus influenzae
and
Neisseria gonorrhoeae
, are necessary for the use of extracellular DNA as the sole source of carbon and energy. These genes also confer a competitive advantage to
E. coli
during long-term stationary-phase incubation. We also show that homologs of these genes are found throughout the proteobacteria, suggesting that the use of DNA as a nutrient may be a widespread phenomenon.
Acquisition and Evolution of theexoULocus inPseudomonas aeruginosa
Authors: Kulasekara Bridget R. , Kulasekara Hemantha D. , Wolfgang Matthew C. , Stevens Lisa , Frank Dara W. , Lory Stephen
Published: May 2006

ExoU is a potentPseudomonas aeruginosacytotoxin translocated into host cells by the type III secretion system. A comparison of genomes of variousP. aeruginosastrains showed that that the ExoU determinant is found in the same polymorphic region of the chromosome near a tRNALysgene, suggesting thatexoUis a horizontally acquired virulence determinant. We used yeast recombinational cloning to characterize four distinct ExoU-encoding DNA segments. We then sequenced and annotated three of these four genomic regions. The sequence of the largest DNA segment, named ExoU island A, revealed many plasmid- and genomic island-associated genes, most of which have been conserved across a broad set of β- and γ-Proteobacteria. Comparison of the sequenced ExoU-encoding genomic islands to the corresponding PAO1 tRNALys-linked genomic island, the pathogenicity islands of strain PA14, and pKLC102 of clone C strains allowed us to propose a mechanism for the origin and transmission of the ExoU determinant. The evolutionary history very likely involved transposition of the ExoU determinant onto a transmissible plasmid, followed by transfer of the plasmid into differentP. aeruginosastrains. The plasmid subsequently integrated into a tRNALysgene in the chromosome of each recipient, where it acquired insertion sequences and underwent deletions and rearrangements. We have also applied yeast recombinational cloning to facilitate a targeted mutagenesis of ExoU island A, further demonstrating the utility of the specific features of the yeast capture vector for functional analyses of genes on large horizontally acquired genetic elements.
Comments: Polymérisation du norbornène par des amorceurs au ruthénium. Etude cinétique de la réaction
Authors: Amass A. J.
Published: May 2006

Comments are expressed on the interpretation of experimental data provided by Tanielian etal. (Can J. Chem. 58, 2813(1980)).
Réponses aux commentaires "Polymérisation du norbornène par des amorceurs au ruthénium. Etude cinétique de la réaction"
Authors: Kiennemann A.
Published: May 2006

The reaction order (between 0 and 1 or between 1 and 2) of the polymerization of norbornene catalyzed by ruthenium initiators is discussed. The role of the solvent and the effect of pretreatment of the catalyst allow the proposal of a reaction scheme of the dissociative type.

[Journal Translation]
Détermination du site de chélation dans des systèmes cycliques arylhydrazone–imine à 6 atomes. Échanges intra- et intermoleculaires du proton chélaté
Authors: Pichon Roger , Gall Jean-Yves Le , Courtot Pierre
Published: May 2006

Chelation sites of the proton and structures of chelated six-atom ring systems have been determined for 2-arylhydrazono-3-aryliminopropane-1-ones and 2-arylhydrazono-1,3-bis(arylimino)propanes. Nuclear magnetic resonance spectroscopy allowed determination in these compounds of two types of exchange of the chelated proton. The first type concerns an intramolecular exchange between the two nitrogen atoms of the hydrazono and imino groups. We have shown that the internal tautomeric equilibria are dependent on several factors (solvent, temperature, and substituents fixed on aromatic rings of azo and imino groups). A second type of exchange corresponds to an intermolecular exchange, most probably of the solute–solute type, which depends on the temperature and concentration of the solutions.
A new cubic-space section model for predicting the specificity of horse liver alcohol dehydrogenase-catalyzed oxidoreductions
Authors: Jones J. Bryan , Jakovac Ignac J.
Published: May 2006

A new active site model for predicting and interpreting the structural- and stereospecificity of horse liver alcohol dehydrogenase-catalyzed oxidations and reductions has been formulated from the specificity, X-ray, and kinetic data now available. The new model is based on a cubic-space system and is convenient and easy to use. The model is completely reliable and permits HLADH specificity towards all of its currently known substrates to be predicted with confidence. Its application is illustrated by analyses of representative examples of major substrate types.
The catalytic cracking of arènes on SiO2–AlPO4 catalysts. A study of the mechanism
Authors: Deyá P. M. , Costa A. , Sinisterra J. V. , Marinas J. M.
Published: May 2006

The catalytic protodealkylation mechanism of arenes (R—Ph), using a SiO2–AlPO4 catalyst has been studied using the microcatalytic pulse technique. Two hydrocarbon series were used: normal series (R = Me, Et, n-Pr, and n-Bu) and α-methylated series (R = Me, Et, i-Pr, and t-Bu). In all cases it was shown that the process may be described by means of Bassett–Habgood's kinetics. That is to say, the process is a first order reaction (r = kPHC) where the rate-controlling step is the surface reaction.Real activation energies of the superficial process have been determined, all results showing values of the same order within the experimental error, which indicates that the transition state is the same for all alkylbenzenes because all the kinetics are first order.Correlations between kinetic constants and electrical (σ*) and steric (Es) parameters have been sought. The best are obtained when values for the α-methylated series are plotted against σ* and those for the normal series against Es.A possible reaction pathway of the SE2 (Ad–E) type is proposed.
Syntheses of derivatives of lacto-N-biose. I. 4,6-Di-O-acetyl-3-O-(tetra-O-acetyl-β-D-galactopyranosyl)-2-deoxy-2-phthalimido-α,β-D-glucopyranosyl chloride
Authors: Lemieux R. U. , Abbas S. Z. , Chung B. Y.
Published: May 2006

Procedures are reported for the synthesis of 4,6-di-O-acetyl-3-O-(tetra-O-acetyl-β-D-galactopyranosyl)-2-deoxy-2-phthalimido-α,β-D-glucopyranosyl chloride, a reagent useful for the reliable introduction of β-D-Galp-(1 → 3)-β-D-GlcNAcp units (lacto-N-biose 1 units) into oligosaccharide structures. A benzyl glycoside intermediate is hydrogenolyzed to the alcohol which is subsequently converted to the glycosyl chlorides by use of the Vilsmeier reagent in the presence of sym-collidine. A comparison is made of the oxazoline method for the preparation of β-glycosides from 2-amino-2-deoxysugars and the phthalimido procedure developed in this laboratory.
Hydrogénation of phosphido bridged ruthenium clusters. A view of P—C bond activation and cleavage in the coordinatively unsaturated molecule Ru3(CO)9(μ2-PPh2)(μ2-H): conversion of μ2-PPh2 to μ3-PPh
Authors: Maclaughlin Shane A. , Carty Arthur J. , Taylor Nicholas J.
Published: May 2006

Treatment of Ru3(CO)8(μ3-η2-C≡CR)(μ2-PPh2)(R = But, Pri) with dihydrogen liberates olefin (CH2=CHR) and generates the coordinatively unsaturated cluster Ru3(CO)9(μ2-PPh2)(μ2-H) which has been shown by X-ray diffraction to have an unprecedented μ2-phosphido bridge in which a P—phenyl group interacts with an electron deficient ruthenium atom. This molecule provides an insight into P—C bond activation leading to cleavage. Further reaction of Ru3(CO)9(μ2-PPh2)(μ2-H) with H2 leads to the phosphinidene cluster Ru3(CO)9(μ3-PPh)(μ2-H)2 via elimination of benzene. Conversion of Ru3(CO)9(μ2-PPh2)(μ2-H) to another phosphinidene cluster Ru4(CO)13(μ3-PPh) occurs on pyrolysis. Hydrogénation of multi-site bound acetylides with H2 is a potentially useful synthetic route to unsaturated clusters. Hydrogenative conversion of μ2-PPh2 to μ3-PPh groups has significance for the synthesis of phosphinidene capped molecules as well as the chemistry of phosphido bridged clusters.
Studies toward polyether antibiotics: stereospecific synthesis of polysubstituted tetrahydropyrans
Authors: Ho Pak-Tsun
Published: May 2006

A stereospecific and general method for the preparation of trans -tetrahydropyrans 1 and cis -tetrahydropyrans 2 from acyclic precursors are described. Compound 12, a possible intermediate for the synthesis of antibiotic X-14547A, has been synthesized.
Abinitio SCF-MO calculations of features of the lowest triplet state potential surfaces of several tetraatomic carbonyl compounds
Authors: Kapur A. , Steer R. P. , Mezey P. G.
Published: May 2006

Non-empirical SCF-MO calculations have been carried out for a series of tetraatomic carbonyl compounds. Portions of the ground singlet and first triplet state potential energy surfaces, in particular those along the out-of-plane bending coordinates, have been determined. Estimates of the first triplet state out-of-plane vibrational frequencies have been calculated.
Charge distributions and chemical effects. XXVI. Relationships between nuclear magnetic resonance shifts and atomic charges for 17O nuclei in ethers and carbonyl compounds
Authors: Béraldin Marie-Thérèse , Vauthier Edouard , Fliszár Sándor
Published: May 2006

The 17O nuclear magnetic resonance shifts of dialkylethers are linearly related to the electron populations on the oxygen atoms, in a range covering L ~ 130 ppm, showing that any increase of electronic charge at the oxygen atom is accompanied by a downfield nmr shift. The opposite trend is observed for the oxygen atoms of ketones and aldehydes.
Copper tetrafluoroborate complexes of the potentially binucleating ligand 1,4-di(2′-pyridyl)aminophthalazine. Mononuclear and polynuclear derivatives
Authors: Dewan John C. , Thompson Laurence K.
Published: May 2006

Three different copper tetrafluoroborate complexes are obtained from the reaction of copper tetrafluoroborate and the title ligand (PAP) in water. Two crystalline modifications of a six-coordinate mononuclear protonated derivative, [Cu(PAPH)2(H2O)2](BF4)4, a triclinic brown form (I) and a monoclinic green form (II), and a dark green polynuclear complex containing neutral ligand and formulated as [Cu3(PAP)2(OH)2](BF4)(BF3OH)3•5H2O (III), are obtained from the same reaction mixture. The hydrolysis of BF4− in water is thought to be responsible for the formation of protonated PAP. In methanol a four-coordinate protonated derivative, [Cu(PAPH)2](BF4)4 (IV) and a binuclear complex [Cu2(PAP)2(H2O)2](BF4)4•0.5MeOH (V), containing neutral ligand, are obtained. The molecular structures of both forms of [Cu(PAPH)2(H2O)2](BF4)4 have been determined by single crystal X-ray diffraction. The brown triclinic form (I) belongs to space group [Formula: see text] with a = 9.856(1), b = 12.724(1), c = 9.401(1) Å, α = 101.691(8), β = 96.717(9), γ = 70.145(8)°, V = 1084.4 Å3, Z = 1. The green monoclinic form (II) belongs to space group P21/n with a = 12.663(4), b = 9.573(3), c = 18.813(4) Å, β = 107.16(2)°, V = 2178.9 Å3, Z = 2. Both complexes have tetragonally distorted six-coordinate structures involving axially bound water molecules and two in plane bidentate protonated ligands. The major difference between the structures involves the axial Cu—O(W) bond lengths (triclinic 2.497(9) Å; monoclinic 2.426(9) Å).
Thermochromism of 1,2,5-triphenylphosphole and the formation of 1,1,2,2-tetrachloro-1,2-diphenylethane from α,α,α-trichlorotoluene
Authors: Hocking Martin B. , Smyth Trevor A.
Published: May 2006

On boiling a yellow solution of 1,2,5-triphenylphosphole in carbon tetrachloride the colour changes to red, reverting to yellow on cooling. This reversible colour change has been conducted in the presence of various additives in an attempt to determine the cause of the colour change. Boiling 1,2,5-triphenylphosphole in α,α,α-trichlorotoluene similarly showed a colour change and gave a coupling product of the solvent, 1,1,2,2-tetrachloro-1-2-diphenylethane. From this evidence and related synthetic, nmr, and esr experiments it is proposed that the colour change of the former system arises from the incipient formation of a phosphole-trichloromethide salt with carbon tetrachloride. With trichlorotoluene the phosphole undergoes more substantive formation of dichlorophenylmethide and possibly chloride salts which undergo further reaction to the observed coupling product.
Acid-catalyzed rearrangement of cyclobutanols. Syntheses of chrysenes, cyclopentenophenanthrenes, and diarylmethanes
Authors: Lee-Ruff Edward , Hopkinson Alan C. , Kazarians-Moghaddam Hira , Gupta Brij , Katz Morris
Published: May 2006

Acid-catalyzed reactions of 8-aryl or 8,8-diarylbicyclo[4.2.0]oct-2-en-7-ols lead to tetrahydrophenanthrene derivatives. For example 8-(1-naphthyl)-bicyclo[4.2.0]oct-2-en-7-ols give substituted chrysenes in methanesulphonic acid. In the case of the homologous 7-aryl or 7,7-diarylbicyclo[3.2.0]hept-2-en-6-ols a novel transformation to diarlymethanes is observed. A mechanism is proposed which accounts for the product distribution observed in these rearrangements.
Microbial hydroxylation of steroids. 8. Incubation of Cn halo- and other substituted steroids with Cn hydroxylating fungi
Authors: Holland Herbert L. , Thomas Everton M.
Published: May 2006

A series of C-21 substituted progesterone derivatives (R = F, Cl, Br, CH3) has been prepared, and incubated the C-21 hydroxylating fungus A. niger. No biotransformation was observed where R = Cl, Br, or CH3, but a minor amount of hydroxylation occurred at an unidentified site where R = F. Two C-11β substituted progesterone derivatives (R = F, OH) were converted to the corresponding C-11 ketone by the C-11α hydroxylator R. stolonifer, but a C-11β hydroxylator (C. lunata) was unable to perform a similar transformation with a C-11α hydroxy substrate. C. lunata hydroxylated a C-11β fluoro substrate at C-14α and C-21 in low yield. C-7α and -7β-hydroxy androst-4-ene-3,17-diones were prepared and incubated with C-7β hydroxylating (R. stolonifer) and C-7α hydroxylating (M. griseocyanus) fungi respectively. No ketone formation was observed. Similarly, the C-6β hydroxylator R. arrhizus was unable to transform a C-6α-hydroxy substrate or C-6α- or C-6β-hydroxy-B-norsteroids. No oxidation at halogen was observed for any of the substrates used. 13C–19F coupling constants for 11β-fluoroprogesterone suggest the presence of through space interactions between fluorine and both C-18 and C-19.
Program PKAS: a novel algorithm for the computation of successive protonation constants
Authors: Motekaitis Ramunas J. , Martell Arthur E.
Published: May 2006

A new algorithm for the simultaneous determination of any number of protonation constants from potentiometric equilibrium data is described. This algorithm is characterized by a unique approach to the internal refinement of the constants and by the analytical nature of the numerical analysis whereby minimization is sought and achieved on the residuals between calculated and observed pH. The FORTRAN IV computer program PKAS utilizing this generalized algorithm has been written and developed and tested on 30 multidentate ligands. The details of the algorithm and the program are described and samples of its recorded usage are provided, indicating its versatility in application.
Resonance Raman spectroscopic evidence for an intramolecular interaction involving the amide and dithioester groups of N-acyl glycine ethyl dithioesters
Authors: Storer A. C. , Ozaki Y. , Carey P. R.
Published: May 2006

The synthesis and resonance Raman spectra of several new N-acyl glycine ethyl dithioesters RC(=O)NH—CH2—C(=S)SR are reported. The resonance Raman spectra of these compounds contain at least two peaks in the "C=S stretching region" between 1050 and 1200 cm−1. The solvent, concentration, temperature, and excitation wavelength dependencies of these features have been investigated. The results obtained are consistent with two conformations of the dithioesters co-existing in solution with the conformational differences being controlled by rotational isomerism about one or both of the NH—CH2 and CH2—CS bonds. Strong support for the existence of more than one conformer in solution comes from the Raman spectrum of a single crystal of N-acetyl glycine ethyl dithioester. In the spectrum of the single crystal several Raman bands are absent compared to the spectrum of the dithioester in solution indicating that only one of the conformers found in the solution phase is retained in the crystal. In one of the conformers found in solution there is evidence for an intramolecular interaction between the amide group and the dithioester group. The exact nature of the intramolecular interaction is uncertain, although simple H-bonding and enethiol tautomerism have been eliminated as possibilities. Possible contributors to the interaction are dipole–dipole forces and amide π-electrons interacting through space with sulfur dx orbitals. Both of these putative interactions would be modulated by rotational isomerism. Based on deuterium substitution experiments a resonance Raman band is identified in the 1050–1200 cm−1 region which contains a contribution from the motion of the amide proton. The unexpected intensity enhancement of an amide mode is attributed to the amide–dithioester intramolecular interaction. The conformer exhibiting the intramolecular interaction is thought to closely resemble the conformation of the substrate in the active site of certain dithioester enzyme–substrate complexes.
Synthesis of β-chloro, β-bromo, and β-iodo α,β-unsaturated ketones
Authors: Piers Edward , Grierson John R. , Lau Cheuk Kun , Nagakura Isao
Published: May 2006

A new, efficient method for the preparation of β-chloro, β-bromo, and β-iodo α,β-unsaturated ketones is described. The method involves the reaction of β-diketones or α-hydroxymethylenecycloalkanones with triphenylphosphine dihalides in the presence of triethylamine. With the dichloride and dibromide reagents, the reactions are conveniently carried out in benzene at room temperature, while with triphenylphosphine diiodide the reactions are best performed in refluxing acetonitrile (β-diketones) or in acetonitrile–hexamethylphosphoramide (α-hydroxymethylenecycloalkanones). The reaction of triphenylphosphine diiodide – triethylamine with a series of 4-alkyl-1,3-cyclohexanediones provides mainly or exclusively (depending on the size of the alkyl group) 6-alkyl-3-iodo-2-cyclohexen-1-ones, while reaction of this reagent with 2-hydroxymethylenecyclohexanone and 2-hydroxymethylenecyclopentanone affords stereoselectively and regioselectively (E)-2-iodomethylenecyclohexanone and (E)-2-iodomethylenecyclopentanone, respectively.
Metal complexes as antioxidants. 9. Application of the spin scavenging technique to the reaction of transition metal dialkyldithiophosphates and dialkyldithiocarbamates with tertiary alkyl hydroperoxides
Authors: Howard J. A. , Yamada T.
Published: May 2006

The spin scavenging technique has been applied to the initial homolytic reaction between tertiary alkyl hydroperoxides and zinc and nickel complexes of dialkyldithiophosphoric acids and dialkyldithiocarbamic acids using low concentrations of Galvinoxyl and 2,2,6,6-tetramethyl-4-oxo-1-piperidinyloxyl as radical scavengers. This method has demonstrated that these transition metal complexes react with hydroperoxides at 303 K to generate free-radicals. Quantitative kinetic data have been obtained from zero-order scavenger decays and the efficiency with which the transition metal complexes generate free-radicals increases in the order Zn[R2NCS2]2 < Zn[(RO)2PS2]2 < Ni[(RO)2PS2]2 < Ni[R2NCS2]2. Deviations from zero-order scavenger decay have been observed, particularly at high complex concentrations, and have been attributed to reaction of the complex with transient radicals to give products which do not react rapidly with the scavenger.
Lignin and related compounds. IX. The isolation of a dimer with a benzylisochroman structure from the hydrogenolysis products of aspen lignin
Authors: Sudo Kenichi , Pepper James M.
Published: May 2006

A dimer with a benzylisochroman structure, 1, has been isolated from the products of the catalytic (Rh—C) hydrogenolysis of aspen lignin.
Relation entre structure et réactivité dans les réactions d'addition nucléophile sur les dérivés carbonylés: influence de la tension angulaire sur la réactivité de cyclanones et cyclanols angulairement contraints
Authors: Boyer Bernard , Lamaty Gérard , Moreau Claude , Geneste Patrick
Published: May 2006

The rate constants for addition of sodium borohydride on the angularly constrained cyclic ketones, tricyclo[3.3.1.1.3,7]-2-decanone (1), bicyclo[3.3.1]-9-nonanone (2), bicyclo[3.2.1.])-8-octanone (3), and bicyclo[2.2.1.]-7-heptanone (4), have been determined in water/dioxane (50:50 v/v) at 25 °C. These values demonstrate the energy differences caused by the changes in torsion angles on passing from the initial state to the transition state. The activation energies determined, representing almost all of the energy associated with the angular torsion, are indicative of a late transition state.Comparison of rate constants for the reduction of these ketones where the reaction site carbon changes from sp2 to sp3 hybridization with the rates for chromic acid oxidation of the corresponding alcohols (opposite change of hybridization) demonstrates that the effects of the angular variations can also act as criteria for the determination of the position of transition states along the reaction pathway.

[Journal Translation]
Influence complexe d'additifs hydrogénés sur le craquage de substances organiques et analogie hydraulique pour la propagation des chaînes. I. Cas d'une pyrolyse à une seule stoechiométrie
Authors: Scacchi Gérard , Baronnet François , Nlclause Michel
Published: May 2006

This first article (I) considers the homogeneous pyrolysis at very low conversion of an organic substance, μH, involving a single principal stoichiometry (μH = m + βH) and proceeding by a mechanism in which the chains are propagated by free radicals (β• and μ•) according to the steps:[Formula: see text]The mechanism "μH, YH" of Niclause and co-workers interprets numerous effects of acceleration, or of inhibition, by hydrogenated additives YH, in the pyrolysis of such organic substances μH.A novel hydraulicanalogy is proposed to describe the propagation of chains in these reactions. This analogy immediately permits a better comprehension of the concept of a step which limits the rate of propagation in the decomposition of pure [μH, namely the bimolecular process [3] in the limiting case [A] where [Formula: see text], or the unimolecular process [2] in the limiting case [B] where [Formula: see text]. The analogy also leads to a better understanding of why a pyrolysis which follows the limiting case [A] (e.g. neopentane) may be accelerated by certain hydrogenated additives (HCl, HBr, H2S), while a thermal decomposition following the limiting case [B] (e.g. ethane) cannot be accelerated by any hydrogenated additive according to this mechanism.In a second article (II), the preceding considerations will be extended to the case of an organic substance μH whose decomposition involves several principal primary stoichiometrics.

[Journal Translation]
Influence complexe d'additifs hydrogénés sur le craquage de substances organiques et analogie hydraulique pour la propagation des chaînes. II. Cas d'une pyrolyse à plusieurs stoechiométries
Authors: Scacchi Gérard , Juste-Darras Clotilde , Baronnet François , Niclause Mlchel
Published: May 2006

A first article (I) considered the simple case of an organic substance μH whose decomposition at low conversion follows a single principal stoichiometry: μH = m + βH. An hydraulicanalogy was introduced in order to describe the propagation of chains in the pyrolysis of μH, either pure or in the presence of a hydrogenated substance YH. Applying the mechanism "μH, YH" of Niclause and co-workers, this analogy leads, in particular, to a better understanding of why certain hydrogenated additives accelerate certain thermal decompositions (e.g. neo-C5H12 = i-C4H8 + CH4), whereas no hydrogenated additive accelerates other pyrolyses (e.g. C2H6 = C2H4 + H2).This second article (II) extends the preceding considerations to the more complex case of an organic substance μH which decomposes according to two principal primary stoichiometries:[Formula: see text]It is shown that the generalized mechanism "μH, YH" and the hydraulicanalogy for the propagation of chains permit an interpretation of the influence of hydrogenated additives (HCl, HBr, H2S, H2, C3H6) on the initial rates of the reactions [A] and [B] in the pyrolysis of propane or of isobutane and on the selectivity of this decomposition (the importance of [A] relative to that of [B]). Finally the still more complex case, in which an organic substance μH decomposes according to morethantwo principal primary stoichiometries, is briefly examined.

[Journal Translation]
Solubilization sites in micellar sodium octylsulphate solutions by ultrasonic spectroscopy
Authors: Jobe David J. , Reinsborough Vincent C. , White Peter J.
Published: May 2006

Relaxation frequencies fc and amplitudes A were measured ultrasonically over the 3.5–52.5 MHz range at 25 °C for the fast exchange of monomer between micelles and bulk solution in micellar sodium octylsulfate solutions with solubihzates present in small amounts. The additives were cyclohexane, pyridine-2-azo-p-dimethylaniline (PADA), benzene, toluene, and p-xylene. Only cyclohexane produced no changes in fc or A. The variations in the relaxational parameters suggested that cyclohexane was situated within the micellar core and PADA, primarily in the surface region of the micelle. Benzene and toluene were adsorbed in minute quantities into the micelle surface but, with additive concentrations beyond a few molecules per micelle, were found principally in the micellar core. Toluene, along with p-xylene, showed an initial dip in fc that may indicate that the first few molecules of these additives were incorporated into the palisade layer of the micelle.
Antitumor activity at the molecular level: binding modes in anthracycline–dinucleotide complexes as determined by optical titration and magnetic circular dichroism
Authors: Bell M. J. , Buchanan G. W. , Hollebone B. R. , Jones E. D.
Published: May 2006

The first application of magnetic circular dichroism (mcd) spectroscopy to drug–dinucleotide binding is reported. The mcd spectra have been recorded for complexes of the intercalating anthracyclines carminomycin, marcellomycin, and aclacinomycin with the dinucleotide CpG. Analysis indicates that drugs having OH groups peri to each anthraquinone carbonyl (i.e. carminomycin and marcellomycin) bind with only one drug molecule in the central hydrophilic region of the nucleotide. By contrast, aclacinomycin, in which one of the anthraquinone carbonyls lacks a peri-OH, is found to cooperatively bind, and has two drug molecules present in the dinucleotide cavity. The cooperativity of binding has been elucidated via an optical titration procedure.
Synthesis of the colitose determinant of Escherichiacoli O111 and 3,6-di-O-(α-D-galactopyranosyl)-α-D-glucopyranoside
Authors: Iversen Tommy , Bundle David R.
Published: May 2006

The syntheses of two branched trisaccharides, which constitute important elements of enterobacterial lipopolysaccharides are described. The common structural feature of each trisaccharide is α-D-glucopyranoside, upon which branching occurs at the O-3 and O-6 positions. Selective blocking of this hexoside at O-2 and O-4 by persistent blocking groups was accomplished by benzylation of 1,6-anhydro-β-D-glucopyranoside (1). Acetolysis of the product 2 afforded a mixture of anomeric triacetates 3 from which the corresponding 3,6-di-O-acetyl-2,4-O-benzyl-α-D-glucopyranosyl chloride (4) was prepared. The α and β 8-methoxycarbonyloctyl glycosides 5 and 6 were obtained in the ratio ~2:1, when 4 was reacted with 8-methoxycarbonyloctanol. Transesterification of the α-glycoside 5 gave the aglyconic intermediate 7 from which each trisaccharide could be obtained in a one step reaction. Thus glycosylation of 7 with tetra-O-benzyl-α-D-galactopyranosyl chloride (8) or 2,4-di-O-benzyl-3,6-dideoxy-α-L-xylo-hexopyranosyl chloride (10) gave the trisaccharides 11 and 13. In both cases removal of blocking groups was achieved in a single hydrogenolysis step. Trisaccharide 12 represents a trisaccharide sequence present in the core saccharide of Salmonella lipopolysaccharides, while the colitose containing trisaccharide 14 is an essential element of the E. coli O111 O-antigen.
Spectral behaviour and solvent effects of some aminoanthraquinone dyes
Authors: Etaiw Safaa H. , Abou Sekkina Morsi M. , El-Hefnawey Gad B. , Assar Samy S.
Published: May 2006

The electronic absorption spectrum of each of nineteen AAQ dyes has been studied in nine different organic solvents. The acid dissociation constants of dyes containing OH, COOH, or SO3H groups have also been determined experimentally. The spectra in ethanol display five bands in the uv region and one in the visible region (450–560 nm). This band is assigned to CT transitions of the type l–aπ which result from the interaction of the lone pair of the nitrogen atom with the phenyl ring of the carbonyl group. The CT nature of the band was supported theoretically and by the effect of solvent on band position.
A synthesis of 11-nor-9-ketohexahydrocannabinol
Authors: ApSimon John W. , Holmes Andrew M. , Johnson Ian
Published: May 2006

A 12-step synthesis of 11-nor-9-keto-hexahydrocannabionol (3) from dimethoxyolivetol (4) is described, together with some ancillary synthetic steps. The key step in this route is the reaction of the unsaturated dinitrile 6 with the Danishefsky diene 10.
Condensation of Schiff bases with 2-oxazolin-5-ones: simultaneous introduction of arylidene and amino moieties
Authors: Mukerjee Arya K. , Kumar Pradeep
Published: May 2006

Schiff bases condense with 2-oxazolin-5-ones having a C-4 methylene and/or C-2 methyl group, and the reaction in glacial acetic acid, containing freshly fused sodium acetate, produces 4-arylidene- and/or 2-styryl-2-imidazoline-5-ones as a result of simultaneous introduction of arylidene and amino moieties.
Enzymes in organic synthesis. 22. Effects of organic solvents on horse liver alcohol dehydrogenase-catalyzed reduction
Authors: Jones J. Bryan , Schwartz Harold M.
Published: May 2006

The effects have been evaluated of up to 30% (v/v) of methanol, ethanol, 2-propanol, tert-butylalcohol, dimethylsulfoxide, sulfolane, acetonitrile, dimethylformamide, N-methyl-2-pyrrolidone, hexamethylphosphoramide, tetrahydrofuran, dimethoxymethane, diglyme, and dioxane on horse liver alcohol dehydrogenase-catalyzed reduction of the representative ketone cyclohexanone. The most viable solvents are those shown in italics on the above list.
Triplet energies of fumaronitrile and maleonitrile
Authors: Wong Po Cheong
Published: May 2006

The triplet energies of fumaronitrile and maleonitrile measured by laser flash photolysis technique using the Herkstroeter–Hammond method are both 59 ± 2 kcal mol−1. Our results show that these olefins are classical triplet energy acceptors for non-electron donating sensitizers. With electron donating sensitizers, quenching through a charge-transfer mechanism also occurs in benzene solution.
Conformational consequences of intramolecular hydrogen bonding by OH to the directional lone-pair of sulfur in derivatives of methyl phenyl sulfide, diphenyl sulfide, and diphenyl disulfide
Authors: Schaefer Ted , Salman Salman R. , Wildman Timothy A. , Clark Peter D.
Published: May 2006

Complete spectral parameters for the 1H nmr spectra of 2-hydroxyphenyl methyl sulfide, 2, 2-hydroxyphenyl phenyl sulfide, 3, bis(2-hydroxy-3-tert-butyl-5-methylphenyl) sulfide, 4, and bis(2-hydroxyphenyl) disulfide, 5, are reported for CCl4 solutions at 305 K. For 2 the parameters are consistent only with a conformation in which the C—S—C plane is roughly perpendicular to the aromatic plane. The conformational determinant is the [Formula: see text] hydrogen bond which forces the mainly 3p orbital on sulfur into the benzene plane. In 3 a similar arrangement is found about the sulfur atom, with the phenyl group lying in the C—S—C plane and therefore perpendicular to the hydroxyphenyl plane (skew conformation). In 4 two [Formula: see text] hydrogen bonds exist, yielding a gable (twist) conformation. Compound 5 exists in the axial conformation with probable C2 symmetry, the CSSC dihedral angle and the CCSS torsion angles all being near 90°. For none of the compounds is there any evidence for [Formula: see text] interactions.
Synthesis and incorporation of [3-3H, U-14C]-L-valine into penicillin V using Penicilliumchrysogenum
Authors: Wolfe Saul , Bowers Raymond John , Lowe David A. , Morin Robert B.
Published: May 2006

The title compound was synthesized by exchange of dimethylpyruvic acid with NaOH–HTO, followed by reductive amination using cyanoborohydride in methanol solvent, resolution of the N-chloroacetyl derivative, and admixture with [U-14C]-L-valine. Degradation of the compound revealed that 94.5% of the tritium was attached to C3, and 5.5% was located on the methyl groups. Incorporation of this doubly labelled valine into penicillin V, purified as the dibenzylamine salt, proceeded with 100.7% loss of the tritium originally present at C3. Commercial [2,3-3H, U-14C]-L-valine, which was found to have 12% of the tritium on the methyl groups, was also incorporated into penicillin V, purified as its methyl ester. Degradation to remove the hydrogen attached to C3 of this ester revealed that no tritium was present at this position. Therefore, in agreement with an earlier result and other related studies, the β-hydrogen of valine is not transferred to C3 of penicillin during the biosynthesis of the latter compound.
The biosynthesis of cyclopropane fatty acids. II. Mechanistic studies using methionine labelled with one, two, and three deuterium atoms in the methyl group
Authors: Buist Peter H. , MacLean David B.
Published: May 2006

The mechanism of formation of monodeuterated cyclopropane fatty acids on administration of L-methione-methyl-d3 to L. plantarum has been investigated. It has been found that the extent of exchange is not affected by the presence of oxygen in the medium, that neither formate-d0 nor formaldehyde-d2 is significantly incorporated into the fatty acid, and that methionine reisolated from the intracellular pool does not contain any exchanged species. These experiments militate against any mechanism involving exchange prior to methyl group transfer. Parallel feeding experiments using methionine labelled in the methyl group with one, two, or three deuterium atoms were carried out and in this way that extent of exchange was quantitated. It was found that at least one-third of the cyclopropane fatty acid from methionine methyl-d3 experiments is derived from an exchanged methyl group. The intramolecular and intermolecular primary deuterium isotope effects for biological cyclopropane ring formation were measured and found to be 3.2 ± 0.5, and 1.01 ± 0.04, respectively. These results are consistent with a mechanism in which a methyl group is transferred in a slow step which is followed by a fast, partially reversible, protonation-deprotonation step.
Synthesis of chalcone ethynylogues with a pharmaceutical objective
Authors: Babin Pierre , Lapouyade Paulette , Dunoguès Jacques
Published: May 2006

A simple route to chalcone ethynylogues, convenient even in the presence of alkoxy or acyloxy substituents, is proposed. This method is based on the use of ethynylsilanes, the involved trimethylsilyl group being recovered during the course of the reaction.
Pyrrole chemistry. XXIV. The Vilsmeier formylation and the cyanation of pyrrole acetals. A synthesis of pyrrole-2,3,5-tricarboxaldehyde
Authors: Loader Charles E. , Barnett Graham H. , Anderson Hugh J.
Published: May 2006

The preparation of the acetals of a number of pyrrole mono- and dicarboxaldehydes is described. It is shown that, provided the reactivity of the unsubstituted ring positions on the pyrrole nucleus is not too low, a carboxyaldehyde or a carbonitrile group may be substituted onto the pyrrole ring using the Vilsmeier reaction or chlorosulfonyl isocyanate respectively. Vilsmeier formylation of the diacetal, 2,4-di(5,5-dimethyl- 1,3-dioxan-2-yl)-pyrrole, followed by hydrolysis gave pyrrole-2,3,5-tricarboxaldehyde.
An improved procedure for the preparation of 3-carbometfaoxy-4-oxotetrahydrothiopyran, 2- and 4-carbomethoxy-3-oxotetrahydrothiophene
Authors: Liu Hsing-Jang , Ngooi Teng Ko
Published: May 2006

An improved procedure for the preparation of the title compounds 1-3 has been developed. Direct condensation of methyl 3-mercaptopropionate with methyl acrylate using sodium hydride as a base gave compound 1 in good yield. The reaction of methyl thioglycolate and methyl acrylate at 0 °C gave compound 2 as the major product whereas at lower temperature (−40 °C) isomer 3 was found as the major product. The condensation reactions of methyl thioglycolate with methyl methacrylate and crotonate were also carried out.
Nucleophilic attack on 2,1-benzisothiazolium salts
Authors: McKinnon David M. , Duncan K. Ann , Millar Lesley M.
Published: May 2006

2,1-Benzisothiazolium salts react with several stabilized carbanions to give products that are derived by attack at the carbon atom of the heterocyclic ring.
Dissociation kinetics of the solvated electron species in methylamine and methylamine–ammonia mixtures
Authors: Harima Y. , Kurihara H. , Nishiki Y. , Aoyagui S. , Tokuda K. , Matsuda H.
Published: May 2006

Potential-sweep voltammetric and potential-step chronoamperometric experiments were made at −50 °C with solvated electrons in methylamine containing LiCl, KI, or CsI. The dissociation rate constants of the ion pairs, (M+•es−), M being alkali metal and es− free solvated electron, were greater than 103 s−1. The pseudo-first-order rate constant of the dissociation of K− into the one-electron species, es− and (K+•es−) in rapid equilibrium, was determined as 40 s−1 by chronoamperometry with 0.5 M KI solutions. The formation constants of K− from the one-electron species determined by chronoamperometry and voltammetry were 4.5 × 104 M−1 and 5.6 × 104 M−1, respectively. An addition of a small amount of ammonia to methylamine caused a decrease in the formation constant of K− and an increase in its dissociation rate constant. The appendix deals with a theoretical treatment of chronoamperograms for an electrode process preceded by the dissociation of a dimer. The boundary value problem was solved by the explicit finite difference method and the analytical method which was based on the concept of reaction layer.
The relation of physical properties of alkanes to connectivity indices: a molecular explanation
Authors: Edward John T.
Published: May 2006

Additive schemes for calculating the molar volumes and heats of vaporization of liquid alkanes from increments characteristic of the numbers and different types of carbon atoms (primary, secondary, tertiary, quaternary), of the mole fraction Zg of gauche conformations, and (where necessary) of other steric factors have been developed. It is suggested that schemes for correlating physical properties of alkanes with connectivity indices mχt are successful because these indices are also correlated with numbers and types of carbon atoms and with Zg.
Thermochemistry of ion exchange and particle interaction in clay suspensions
Authors: Schramm Laurier L. , Kwak Jan C. T.
Published: May 2006

The measurement of enthalpies of ion exchange for a number of homovalent and heterovalent exchange pairs by titration calorimetry is described. A self-consistent addition to previous measurements on such systems is reported. In addition to the enthalpies of ion exchange the heats of tactoid formation and breakdown were observed. The apparent heat of tactoid formation for the Na–Ca exchange pair is estimated to be −4.9 kJ per equivalent of ion exchange.
The single crystal electronic spectra of cis-octahedral nickel(II) diamine complexes at 10 K
Authors: Lever A. B. P. , Walker I. M. , McCarthy P. J.
Published: May 2006

The single crystal polarised spectra, at 10 K, of a series of nickel(II) complexes containing the cis-chromophore NiN4O2 are reported. The four N ligands are provided by the diamines N,N′-diethylethylenediamine or meso-stilbenediamine, and the two O ligands by chelating nitrate or nitrite ion. The spectra are assigned in the point group C2v(III). The energies are calculated within the Normalised Spherical Harmonic Hamiltonian and the Orbital Angular Overlap formalisms. The parameters so derived are consistent with previous experience obtained with trans-analogs once the small bite of the chelating nitrite ligand is accounted for.
Apparent carbon–carbon bond cleavage in an epoxide. 2,3,4,5,6-Hexachloro-12-oxopentacyclo[5.4.1.1.8,11.03,10.05,9]tridecane; a minor product from the acid treatment of endrin
Authors: ApSimon John W. , Yamasaki Kazu , Fruchier Alain , Chau Alfred S. , Huber Carol P.
Published: May 2006

The treatment of endrin (1) with sulfuric acid produces ketoendrin 2 and from 6 to 8% of another product that we show to be 2,3,4,4,5,6-hexachloro-12-oxapentacyclo[5.4.1.1.8,11.03,10.05,9]tridecane 3, based initially on spectral evidence and confirmed by a single crystal X-ray diffraction study. The formation of 3 involves an apparent and unusual carbon–carbon single bond cleavage in an epoxide accompanied by cycloaddition to a proximate carbon–carbon double bond. This transformation probably proceeds by the route outlined in ref. 1. Some of the observed nmr parameters of 3 are discussed in the light of its structure and a comparison is made with the observed spectra for endrin (1).