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The arene–alkene photocycloaddition  [cached]
Ursula Streit,Christian G. Bochet
Beilstein Journal of Organic Chemistry , 2011, DOI: 10.3762/bjoc.7.61
Abstract: In the presence of an alkene, three different modes of photocycloaddition with benzene derivatives can occur; the [2 + 2] or ortho, the [3 + 2] or meta, and the [4 + 2] or para photocycloaddition. This short review aims to demonstrate the synthetic power of these photocycloadditions.
Reactivity and Synthetic Applications of 4,5-Dicyanopyridazine: An Overview  [PDF]
Renzo Alfini,Marco Cecchi,Donatella Giomi
Molecules , 2010, DOI: 10.3390/molecules15031722
Abstract: Despite the poor reputation of electron-deficient pyridazines in intermolecular Hetero Diels-Alder (HDA) reactions, 4,5-dicyanopyridazine (DCP) showed a surprising reactivity as a heterocyclic azadiene in inverse electron-demand HDA processes with different dienophiles. The use of alkenes, alkynes and enamines as 2p electron counterparts afforded dicyanocyclohexa-1,3-dienes and substituted phthalonitriles, respectively, while the use of suitable bis-dienophiles provides a general strategy for the one-pot synthesis of polycyclic carbo- and hetero-cage systemsthrough pericyclic three-step homodomino processes. HDA reactions with heterocyclic dienophiles allowed direct benzoannelation: in particular, pyrrole and indole derivatives were converted to dicyano-indoles and -carbazoles. In addition an unprecedented reactivity of DCP as a very reactive heterocyclic electrophile at the C-4 carbon was also evidenced: by changing the experimental conditions, cyanopyrrolyl- and cyanoindolyl-pyridazines were obtained through reactions of pyrrole and indole systems as carbon nucleophiles in formal SNAr2 processes where a CN group of DCP acts as leaving group. Thus, careful control of the reaction conditions allows exploitation of both pathways for the synthesis of different classes of heterocyclic derivatives.
On the Reactivity of α-(Triphenylphosphoranylidene)-benzylphenylketene with Nitrogen Compounds: Synthetic and Mechanistic Implications
Cunha, Silvio;Kascheres, Albert;
Journal of the Brazilian Chemical Society , 2002, DOI: 10.1590/S0103-50532002000500025
Abstract: the reactivity of α-(triphenylphosphoranylidene)-benzylphenylketene, a stabilized phosphorus ylide derived from diphenylcyclopropenone, toward nitrogen compounds was investigated. particularly, the reaction of diethyl azodicarboxylate with α-(triphenylphosphoranylidene)-benzylphenylketene provides a new route to polysubstituted n-acyl carbamates.
On the Reactivity of a-(Triphenylphosphoranylidene)-benzylphenylketene with Nitrogen Compounds: Synthetic and Mechanistic Implications  [cached]
Cunha Silvio,Kascheres Albert
Journal of the Brazilian Chemical Society , 2002,
Abstract: The reactivity of alpha-(triphenylphosphoranylidene)-benzylphenylketene, a stabilized phosphorus ylide derived from diphenylcyclopropenone, toward nitrogen compounds was investigated. Particularly, the reaction of diethyl azodicarboxylate with alpha-(triphenylphosphoranylidene)-benzylphenylketene provides a new route to polysubstituted N-acyl carbamates.
Trypanosoma rangeli infected mouse sera reactivity with Trypanosoma cruzi synthetic peptides
ZUNIGA,CLAUDIO; VARGAS,RAMON; PALAU,MARIA TERESA; BELLO,FELIO; DE DIEGO,JOSé ANTONIO; VERGARA,ULISES;
Parasitología latinoamericana , 2007, DOI: 10.4067/S0717-77122007000100001
Abstract: in man, differential diagnosis of trypanosoma cruzi and trypanosoma rangeli infections represents a serious problem, not only because both parasites present similar geographical distribution, the same hosts and sometimes the same insect vector, but also because they have common antigen determinants. in this work igm and igg humoral responses to t. cruzi syntethic peptides in mice infected with t. cruzi and with t. rangeli were analysed. in a immunoradiometric assay (irma ) 6 syntethic peptides were used, denominated as clones 1, 2, sapa, 13, 30 and 36. the results showed that sera from infected mice with t. rangeli recognized all peptides derived from t. cruzi proteins, at igm as well as igg level. reactivity with peptide sapa is discussed as previous work indicated that sapa is not codified in the t. rangeli genome. our results support the suggestion that crossed reactions are due to the fact that both parasites present common antigens
Trypanosoma rangeli infected mouse sera reactivity with Trypanosoma cruzi synthetic peptides  [cached]
CLAUDIO ZUNIGA,RAMON VARGAS,MARIA TERESA PALAU,FELIO BELLO
Parasitología latinoamericana , 2007,
Abstract: In man, differential diagnosis of Trypanosoma cruzi and Trypanosoma rangeli infections represents a serious problem, not only because both parasites present similar geographical distribution, the same hosts and sometimes the same insect vector, but also because they have common antigen determinants. In this work IgM and IgG humoral responses to T. cruzi syntethic peptides in mice infected with T. cruzi and with T. rangeli were analysed. In a immunoradiometric assay (IRMA ) 6 syntethic peptides were used, denominated as clones 1, 2, SAPA, 13, 30 and 36. The results showed that sera from infected mice with T. rangeli recognized all peptides derived from T. cruzi proteins, at IgM as well as IgG level. Reactivity with peptide SAPA is discussed as previous work indicated that SAPA is not codified in the T. rangeli genome. Our results support the suggestion that crossed reactions are due to the fact that both parasites present common antigens
Alkene selenenylation: A comprehensive analysis of relative reactivities, stereochemistry and asymmetric induction, and their comparisons with sulfenylation  [cached]
Vadim A. Soloshonok,Donna J. Nelson
Beilstein Journal of Organic Chemistry , 2011, DOI: 10.3762/bjoc.7.85
Abstract: A broad perspective of various factors influencing alkene selenenylation has been developed by concurrent detailed analysis of key experimental and theoretical data, such as asymmetric induction, stereochemistry, relative reactivities, and comparison with that of alkene sulfenylation. Alkyl group branching α to the double bond was shown to have the greatest effect on alkene reactivity and the stereochemical outcome of corresponding addition reactions. This is in sharp contrast with other additions to alkenes, which depend more on the degree of substitution on C=C or upon substituent electronic effects. Electronic and steric effects influencing asymmetric induction, stereochemistry, regiochemistry, and relative reactivities in the addition of PhSeOTf to alkenes are compared and contrasted with those of PhSCl.
Biovailability and stability of erythromycin delayed release tablets
Sydney Ogwal, T.U. Xide
African Health Sciences , 2001,
Abstract: Background : Erythromycin is available as the free base, ethylsuccinate, estolate, stearate, gluceptate, and lactobionate derivatives. When given orally erythromycin and its derivatives except the estolate are inactivated to some extent by the gastric acid and poor absorption may result. Objectives : To establish whether delayed release erythromycin tablets meet the bioequivalent requirement for the market Methods : Spectrophotometric analysis was used to determine the dissolution percentage of the tablets in vitro. High performance liquid chromatography and IBM/XT microcomputer was used to determine the biovailability and pharmacokinetic parameters in vivo. Results : Dissolution percentage in thirty minutes reached 28.9% and in sixty minutes erythromycin was completely released. The parameters of the delayed release tablets were Tlag 2.3hr,Tmax.4.5hr, and Cmax 2.123g/ml Ka 0.38048hr-1 T _ 1.8 hr, V*C/F 49.721 AUC 12.9155.The relative biovailability of erythromycin delayed release tablet to erythromycin capsules was 105.31% Conclusion : The content, appearance, and dissolution biovailability of delayed release erythromycin tablets conforms to the United States pharmacopoeia standards. The tablets should be stored in a cool and dry place in airtight containers and the shelf life is temporarily assigned two years. African Health Sciences 2001; 1(2):90-96
Combined use of an alkene and a phosphine as a nucleophilic catalyst system for the cyanosilylation of carbonyl compounds
Xiu Wang,Fan Fang,ShiKai Tian
Chinese Science Bulletin , 2010, DOI: 10.1007/s11434-010-4029-z
Abstract: The catalytic potential of carbon nucleophiles has seldom been disclosed due to their reactivity toward carbon electrophiles to form stable carbon-carbon bonds, which are too strong to be cleaved for the expected catalytic cycles. We have developed an efficient catalytic cyanosilylation of carbonyl compounds with an in situ generated alkene/phosphine adduct, which is tuned not to couple with a carbonyl compound or an electron-deficient alkene under the reaction conditions when its nucleophilicity is translated into catalytic activity. In the presence of 3 mol% of methyl acrylate and 3 mol% of triphenylphosphine, a broad range of alkyl, alkenyl, and aryl ketones and aldehydes undergo cyanosilylation reaction with trimethylsilyl cyanide at room temperature to yield structurally diversified cyanohydrin silyl ethers in excellent yields. By using methyl acrylate/triphenylphosphine as a highly effective nucleophilic catalyst system for the cyanosilylation of carbonyl compounds, this study demonstrates a new concept for the development of useful organocatalysis utilizing the nucleophilicity of alkene/phosphine adducts generated in situ.
Investigation of the reactivity patterns of antifilaggrin antibodies in sera and synovial fluids from patients with rheumatoid arthritis using citrullinated synthetic peptides
M Brózik, J Szakonyi, A Magyar, B Rojkovich, R Tobi, F Hudecz, P Gergely, K Merétey
Arthritis Research & Therapy , 2003, DOI: 10.1186/ar632
Abstract: Recent studies have shown that their production is highly specific for rheumatoid arthritis (RA) and the initial antigenic trigger for these autoantibodies can be localised to the inflammed synovial tissue.The aim of our study was to compare the reactivity and specificity of antibodies in sera and synovial fluids towards citrullinated epitopes. Peptide sequence corresponding to human profilaggrin (amino acid residues 306–324) and sequences with citrulline substitution at different positions were synthetised by mutipin peptide synthesis on solid supports. Shortened versions of the peptide were also produced by removal of amino acid residues from its N and C terminals. Completely citrullinated variant of the 14-mer peptide was also prepared. Peptide with no citrulline replacement was used as a control antigen. We found significant differences in the sensitivity for RA of 19 individual peptides tested (from 5% to 68%), reflecting previous results that the surrounding amino acids play an important role in creation of an autoantigenic epitope. Further, we tested the reactivities of paired serum and synovial fluids and found very similar peptide recognition patterns in serum and synovial IgG from the same individuals. Studies on larger number of samples are in progress to evaluate the results statistically that may support further evidence of the synovial origin of antifilaggrin autoantibodies.This work was supported by the Hungarian grant OTKA T037876.
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