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Crystal forms of polyethersulfones (PES) were investigated by using a model compound and a low molecular weight oligomer. These are amorphous as-synthesized, and can undergo solvent-induced crystallization under the appropriate conditions. The model compound, 4,4'-bis(p-methoxyphenoxy)diphenyl sulfone, yielded monocrystals, and its structure was solved using X-ray diffraction. Conformational disorder is present, two conformers cohabiting in 55:45 proportions. This model compound, combined to previous structural studies published in the literature, served as a basis for conformational studies of polyethersulfone. Low molecular weight polymers submitted to solvent-induced crystallization resulted in a PES crystal form different from that previously published in the literature, as shown by powder X-ray diffraction. Key words: polyethersulfone, solvent-induced crystallization, crystal structure, polymorphism, X-ray diffraction. On a etudie les formes cristallines de sulfones de polyethers (SPE) en se basant sur un compose modele et un oligomere de faible poids moleculaire. Ces sont des produits amorphes obtenus par une synthese-as et, dans des conditions appropriees, ils peuvent donner lieu a une cristallisation induite par un solvant. Le compose modele, le sulfone de 4,4'-bis(p-methoxyphenoxy)diphenyle, peut etre isole sous la forme de monocristaux et on a determine sa structure par diffraction des rayons-X. On a decele un desordre conformationnel alors que deux conformeres coexistent dans des proportions de 55 : 45. Les donnees relatives au compose modele combinees aux etudes publiees anterieurement sur les structures ont servi de base pour les etudes conformationnelles des sulfones de polyethers. Les polymeres de faibles poids moleculaires soumis a une cristallisation induite par un solvant ont conduit a la formation de SPE dont la forme cristalline, d'apres la diffraction des rayons-X, serait differente de celles rapportees anterieurement dans la litterature. Mots-cles : sulfone de polyether, cristallisation induite par un solvant, structure cristalline, polymorphie, diffraction des rayons X. [Traduit par la Redaction], Introduction Polyethersulfones, abbreviated PES, stand out among other high-performance thermoplastic polymers because of their thermal stability, amorphous morphology, and good solubility in low polarity solvents (ketones and chlorinated aromatic hydrocarbons). [...]

Recent laboratory studies have demonstrated that isoprene oxidation products can partition to atmospheric aerosols by reacting with condensed phase sulfuric acid, forming low-volatility organosulfate compounds. We have identified organosulfate compounds in free tropospheric aerosols by single particle mass spectrometry during several airborne field campaigns. One of these organosulfates is identified as the sulfate ester of IEPOX, a second generation oxidation product of isoprene. The patterns of IEPOX sulfate ester in ambient data generally followed the aerosol acidity and N[O.sub.x] dependence established by laboratory studies. Detection of the IEPOX sulfate ester was most sensitive using reduced ionization laser power, when it was observed in up to 80% of particles in the tropical free troposphere. Based on laboratory mass calibrations, IEPOX added >0.4% to tropospheric aerosol mass in the remote tropics and up to 20% in regions downwind of isoprene sources. In the southeastern United States, when acidic aerosol was exposed to fresh isoprene emissions, accumulation of IEPOX increased aerosol mass by up to 3%. The IEPOX sulfate ester is therefore one of the most abundant single organic compounds measured in atmospheric aerosol. Our data show that acidity-dependent IEPOX uptake is a mechanism by which anthropogenic S[O.sub.2] and marine dimethyl sulfide emissions generate secondary biogenic aerosol mass throughout the troposphere. acid-catalyzed particle phase reactions | epoxides | free troposphere | secondary organic aerosol doi: 10.1073/pnas.1012561107

One-electron reduction of methanesulfonyl chloride in the presence or in the absence of oxygen and the ability of MeS[O.sub.2.sup..] radical to act as oxidant and as catalyst in the cis-trans isomerization of unsaturated fatty acids is described. Unambiguous evidence is provided for a long-lived electron adduct to sulfonyl chlorides, which has acted as reductant and has established equilibrium with [O.sub.2.sup..-].

Diels-Alder reactions of 4-alkenylthiazoles were carried out to find a new approach to thaizole functionalization. Diels-Alder reactions included reactions of N-substituted maleimides, maleic anhydride and napthoquinone with high levels of stereocontrol to give the corresponding endo-cycloadducts.

Asymmetric synthesis of ring functionalized trans-2,6-disubstituted piperidines from N-sulfinyl [delta]-amino [beta]-keto phosphonates was carried out. The method involves the one-pot conversion of sulfinimine-derived N-sulfinyl [delta]-amino [beta]-ketophosphonates, the stereoselective addition of organocuprates and one the one-pot dephosphorylation of the 3-phosphoryl piperidiens.

A series of sulfonated poly(p-phenylene terephthalamide) (PPTA) polymers are prepared in three molecular configurations. The variation in the polymer alignment is due to the result of the differences in the solution properties and the film forming process.

A review of the efforts made since 1975 to understand the chemistry of a select group of sulfur-nitrogen compounds including sulfinimines and N-sulfonyloxaziridines is presented. It is observed that the exploration of sulfenamides led to the discovery of sulfenimines and sulfinimines and, ultimatley, to the invention of N-sulfonyloxaziridines and enantiopure sulfinimines.

The femtosecond pump-probe transient absorption spectroscopy is used to measure the ultrafast time-resolved electronic spectra of primary events induced in copper tetrasulfonated phthalocyanine Cu[(tsPc).sup.4-]) in aqueous solution. Combining of spectroscopy and electrochemical measurements gives clear interpretation of primary events upon light excitation, photochemical mechanisms and spectral features relating to photophysical and photochemical mechanisms.

An iodocyclization of sulfinimine-derived enantiopure homoallylic sulfonamides that represents a valuable new route for the asymmetric synthesis of trans-2,5-disubstituted pyrrolidines is described. The homoallylic sulfonamides were prepared from readily available sulfinimine-derived beta-amino aldehydes using the Wittig reaction and were obtained as E:Z mixtures.

Enantiopure aromatic (phenyl, naphthyl) and heteroaromatic (pyridyl, quinolyl, diazinyl) sulfoxides are synthesized by reaction of (S)-tert-butyl tert-butanethiosulfinate with aryl- or heteroaryllithium derivatives. An application of an enantiopure aminosulfoxide as N,S ligand for the asymmetric catalysis of allylic nucleophilic substitution is successfully tested.

Seven model substrates were synthesized and cyclized to examine the structural features responsible for imparting diastereoselection in the second intramolecular Heck reaction. The study demonstrate that stereoselection in the formation of the second spirooxindole ring results from the avoidance of steric interactions in the insertion step with the spirooxindole formed in the first Heck cyclization.

The regiospecificity of the 1,4-addition of the reported novel alkoxy chlorodisulfides to 2-methyl-1,3-butadiene is established. Periodate oxidation at room temperature, preferably in the presence of I(sub 2), resulted in oxidative cleavage and cyclization to beta-iodo alpha-beta-unsaturated gama-sultines that were also conveniently prepared by reaction of iodine with alkyl allenesulfinates.

A facile and efficient synthetic route toward highly substituted 2,3-dihydrothiopyran-4-ones was developed through a formal [5C + 1S] annulation of readily available alpha-alkenoyl ketene-(S,S)-acetals with sodium sulfide nonahydrated salt (Na(sub 2)S.9H(sub 2)O) and utilized in the synthesis of 2-(4-chlorophenyl)-6-(morpholin-4-yl)-4H-thiopyran-4-one, an inhibitor of DNA-dependent protein kinase (DNA-PK).

Beta-sultams are the sulfonyl analogues of beta-lactams and N-acyl beta-sultams are novel inactivators of the class C beta-lactamase of Enterobacter cloacae P99. The analogous N-acyl beta-lactams undergo enzyme-catalyzed hydrolysis, the rate of which is compatible with significant amide anion expulsion/S-N fission in the transition state, and the enzyme reaction displays a later transition compared with hydrogen-ion-catalyzed hydrolysis of the beta-sultam.

The assimilation and transformation of phytoplankton-derived organic sulfur compound dimethylsulfoniopropionate (DMSP) by bacteria during the microcosm experiment and relation between the changes in DMSP processing and the changes in the composition of the bacterial assemblage during the induced bloom compared to nonbloom conditions are investigated. The results show that the composition of the bacterial assemblage and the contribution of DMSP to the overall dissolved organic sulfur/organic matter pool control how efficiently bacteria assimilate DMSP S and thereby potentially divert it from DMS production.

The structure and energetics of the simplest vic-disulfoxide CH3S(O)S(O)CH3 and its key isomers are reported. The B3LYP structure obtained for 5,5-di-t-butyltetrathiolane-2, 3-dioxide reproduces the essential structural parameters of the known vic-disulfinyl compound, 5-(1-adamantyl)-5-tert-butyltetrathiolane-2,3-dioxide.

It has been demonstrated that the D parameter of the tetraradicals and hexaradicals is mainly determined by the spin density of the localized 1,3-cyclopentanediyl spin carrier. Thus the trimethylenebenzene ferromagnetic coupler is essentially negligible.

The preparation, X-ray crystal structure, electrochemical and magnetic characterization of a 1:1 copper complex [C[u.sup.II][(hfac).sub.2](TTF-CH=N-Py)] (imine-bridged pyridyltetrathiafulvalene building block) are reported. The crystal structure reveals that the imine N atom participates in chelation to the paramagnetic center which makes the ligand an attractive precursor for assembly of [pi]-d systems.

Bis(dialkylamide)hydrogen dibromobromate is used as a source of BrO(super -), and is shown that rates of dephosphorylation are similar with BrO(super -) generated from these complexes or from Br2-H2O. Reactions of 4-nitrophenyl tosylate, with BrO(super -) are rapid with 0.1 M BrO(super -), under conditions in which oxidations of organic sulfides are too fast to be followed by conventional methods.

The UV-vis spectroscopy technique is employed to explain the mechanisms involved in the reactions of stabilized and semistabilized sulfur ylides with benzhydrylium ions. The various advantages and issues related to the application of sulfur ylides for the purpose of cyclopropanations are explained.

Several first-principles bottom-up investigations of the TTTA (1,3,5-trithia-2,4,6-triazapentalenyl) crystal are conducted to explain the magnetic bistability exhibited by the molecule-based magnets. The observed bistability is shown to be a result of the coexistence of monoclinic high temperature and triclinic low temperature phases.

The article explains the synthesis of an unprecedented luminescent polynuclear gold (I) [[mu].sub.3]-sulfido cluster, which is shown to exhibit a thiacrown-like architecture. The addition of [CH.sub.3]CN compound is shown to lead to numerous binding and spectroscopic changes in the system.

The functional characterization of a novel protein NosA in nosiheptide biosynthesis has provided an unusual C-terminal amide forming strategy in general for maturing certain amide-terminated thiopeptides by processing their precursor peptides featuring a serine extension. NosA has acted as an intermediate bearing a bis-dehydroalanine tail and has catalyzed an enamide dealkylation to remove the acrylate unit originating from the extended serine residue.

Solvent-free synthesis of a series of alkylthio-substituted titanyl phthalocyanine (TiOPc) derivatives starting from the corresponding phthalonitriles (Pn) is reported. The process eliminated the formation of the unmetalated phthalocyanine ([H.sub.2]Pc), a side product that makes purification difficult and the alkylthio groups in the obtained derivatives enhance solubility in common organic solvents and shift the absorption to the near-IR region.

The first mechanistic insight into 2-thiosugar production in an angucycline-type antibiotic, BE-7585A, is reported. The results indicated that the sulfur insertion mechanism in 2-thiosugar biosynthesis shares similarities with that for thiamin biosynthesis.

A newly developed amino-thiocarbamate-catalyzed bromolactonization of unsaturated carboxylic acids is described. The newly developed protocol could be applied in the enantioselective synthesis of the key intermediates of VLA-4 antagonists.

A highly efficient and convenient strategy is described that has allowed rapid construction of unique optically active spiro[oxazoline-3,3' -oxindole]s through the organocatalyzed asymmetric synthesis of spirocyclic thiocarbamates via an aldol reaction. The evaluation of the spirooxazolines using a model of acute neuroinflammation has shown antipyretic activity and has provided an opportunity to discover new antipyretic agents.

The study employs a two-step process, which helps in the identification of special monothiophosphate-modified aptamers (thioaptamers) that can bind to the hyaluronic acid binding domain (HBAD). These thioaptamers are shown to be extremely beneficial and can be used as a targeting agent during the delivery of therapeutic payloads.

Linear conjugated guest molecules with high aspect ratios have formed inclusion compounds with guanidinium organodisulfonate (GDS) host frameworks in which organodisulfonate ' pillars' have connected opposing GS sheets to generate lamellar architectures that reflect templating by the guest. The effects of the different framework architectures and packing motifs are marked as bathochromic shifts in the absorption and emission spectra of the guest when compared with their spectra in methanol solutions.

A novel polyketide metabolite, thailandamide lactone, which is not detected in the wild type, is isolated from the mutant broth, and its structure is analyzed by high-resolution mass spectrometry and IR and NMR spectroscopy. In a biological assay tumor cell lines, thialandamide lactone has displayed moderate antiproliferative activities.

Benzothiazinones (BTZs) have formed a new class of potent antimycobacterial agents. BTZs are activated in the bacterium by reduction of an essential nitro group to a nitroso derivative, which has reacted with a cysteine residue in the active site of decaprenylphosphoryl-[beta]-D-ribose 2E-epimerase (DprE1) of Mycobacterium tuberculosis.

Methionine sulfoxide reductases MsrA and MsrB are shown to be involved in the regulation of mitochondrial function. The results have shown that oxidative stress has contributed to mitochondrial dysfunction through oxidation of methionine residues in proteins located in different cellular compartments.

Cysteamine has reduced selenocystamine to form hemiselenocystamine and then cystamine and their rate constants are similar for reactions of cysteine/selenocystine. The reaction rates of selenium as a nucleophile and as an electrophile are 2-3 and 4 orders magnitude higher than those of sulfur.

The reanalysis of the kinetics and molecularity of the Newman-Kwart rearrangement of N,N-dimethyl O-(p-nitrophenyl)thiocarbamate in N,N-dimethylacetamide solvent is described. The studies have shown that under the microwave heating conditions, a delayed negative feedback signal to the microwave power balancing loop has resulted in oscillatory reaction overheating and due to higher tan [delta] in the solute the amplitude of the oscillation has increased with the concentration of N,N-dimethyl O-(p-nitrophenyl)thiocarbamate.

A general and efficient method is described for preparing 2,4-di- and trisubstituted thiazoles through p-TsOH.[H.sub.2]O-catalyzed cyclization of trisubstituted propargylic alcohols with thioamides. The reaction is achieved in under mild conditions that has not required the exclusion of air and moisture and has provided a convenient route to the synthetically useful aromatic heterocycle.

A general and robust racemization-free protocol is described for preparing a variety of N-tert-butanesulfinyl ketimines. The reaction progress is monitored by [super 1]H NMR by using the nonperturbing internal standard diglyme and ketimines are formed in either THF or CPME (cyclopentyl methyl ether) as solvent with heating to reflux.

Consecutive ring-expansion reactions of oxiranes with dimethylsulfoxonium methylide are analyzed and modeled at the density functional theory (DFT) and second-order Moller-Plesset (MP2) levels of theory by using a polarizable continuum model (PCM) to account for solvent effects. The studies have shown the complete conversion of the enantiomeric purities for the nucleophilic ring expansions of enantiomeric 2-mono- and 2,2-disubstituted epoxides and oxetanes with dimethylsulfoxonium methylide.

The examination of the pH-dependent mutarotation of 1-thioaldopyranoses in aqueous media is presented. 1-Thio-D-mannopyranose and 1-thio-D-altropyranose has displayed very strong pH dependence where the anomeric equilibrium ratios have changed from a preference for the [beta]-anomer at lower pH to the [alpha]-anomer at higher pH.

The synthesis, structure, redox and photophysical properties of the two- and three-layered donor-acceptor (D-A) type [3.3]paracyclophanes ([3.3]PCPs) are presented. The (p-ethylbenzenesulfonyl)methyl isocyanide coupling method is used for achieving the synthesis of the two- and three-layered [3.3]PCPs containing 2,1,3-benzothiadiazole (BTD) as an acceptor.

G enetic i nterception and s tructural c haracterization of t hiopeptide c yclization p recursors for thiocillins (tclM) from Bacillus cereus is described. The studies provide insight into the TclM and its homologues in other thiazolyl peptide producing strains as the enzymes reponsible for the trans-annular heteroannulation at core of this class of molecules.

Silver(I) activation of thioacetoacetates in the presence of ketones has produced 1,3-dioxin-4-ones. The mechanistic studies addressing the intermediacy of an acylketene intermediate are presented.

Novel N-(Cbz-aminoacyl)thiosemicarbazides are cyclized by treatment with sulfuric acid to produce 1,3,4-thiadiazoles. These compounds have reacted with N-(Cbz-aminoacyl)- and - dipeptidoylbenzotriazoles to produce chirally pure 1,3,4-thiadiazol-2-yl-substituted amino acids and dipeptides.

Nine [beta]-hydroxy-[alpha]-sulfenyl[gamma]-butyrolactones having different substituents are prepared and crystal structures of syn-syn lactones are determined. The X-ray and theoretical studies have shown that two concomitant, attractive 1,4-intramolecular interactions of divalent sulfur with both carbonyl and hydroxyl oxygens are the driving force for the stereochemical preference and the nonbonded sulfur-oxygen interactions have controlled the stereoselectivity of the reaction.