- INTRAMOLECULAR DIELS-ALDER REACTIONS OF ETHYL 2,4,9-DECATRIENOATE AND 2,4,10-UNDECATRIEONATE
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The title compounds undergo intramolecular Diels-Alder reactions at 180 deg C to give ester-substituted hydrindane and decalin ring systems, with trans/cis ratios of 43:57 and 50:50, respectively.
- Lin, Yi-Tsong,Houk, K. N.
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Read Online
- Synthesis of 7,6-fused bicyclic lactams for use as beta-turn mimics
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An improved synthesis of the 7,6-fused bicyclic lactam is presented starting from readily available chiral starting materials. (S)-allylglycine is protected as the phthalimide derivative and coupled with (S)-2-amino-6- hydroxyhexanoic acid methyl ester. Oxidation of the hydroxyl group to the aldehyde followed by enamide synthesis and acyl iminium ion cyclization provide the bicyclic system as a single diastereomer in good overall yield. Copyright Taylor & Francis Group, LLC.
- Morales, Omar,Seide, Wesley,Watson, Samuel
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- Quinolinium Bichromate Oxidation of Diols: A Kinetic Study
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Quinolinium dichromate (QDC) in water oxidizes vicinal and nonvicinal diols to the corresponding α-hydroxy carbonyl compound. The rate is proportional to the concentrations of diol, oxidant and hydrogen ions, and the reactions proceed almost twice as fast in D2O than in H2O. These data can be correlated with a mechanistic pathway involving the intermediate formation of a chromate ester, which undergoes decomposition to give the product.
- Kuotsu, Bernadette,Tiewsoh, Enboklin,Debroy, Abhijit,Mahanti, Mahendra K.
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- Synthetic Studies towards Ptilomycalin A using a Biomimetic Approach
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Two model compounds, the tetracycle 2 and the tricycle 9 are prepared using a biomimetic synthetic approach to the guanidine-containing natural product ptilomycalin A 1.
- Murphy, Patrick J.,Williams, Harri Lloyd,Hursthouse, Michael B.,Malik, K. M. Abdul
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Read Online
- Dual utility of a single diphosphine-ruthenium complex: A precursor for new complexes and, a pre-catalyst for transfer-hydrogenation and Oppenauer oxidation
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The diphosphine-ruthenium complex, [Ru(dppbz)(CO)2Cl2] (dppbz = 1,2-bis(diphenylphosphino)benzene), where the two carbonyls are mutually cis and the two chlorides are trans, has been found to serve as an efficient precursor for the synthesis of new complexes. In [Ru(dppbz)(CO)2Cl2] one of the two carbonyls undergoes facile displacement by neutral monodentate ligands (L) to afford complexes of the type [Ru(dppbz)(CO)(L)Cl2] (L = acetonitrile, 4-picoline and dimethyl sulfoxide). Both the carbonyls in [Ru(dppbz)(CO)2Cl2] are displaced on reaction with another equivalent of dppbz to afford [Ru(dppbz)2Cl2]. The two carbonyls and the two chlorides in [Ru(dppbz)(CO)2Cl2] could be displaced together by chelating mono-anionic bidentate ligands, viz. anions derived from 8-hydroxyquinoline (Hq) and 2-picolinic acid (Hpic) via loss of a proton, to afford the mixed-tris complexes [Ru(dppbz)(q)2] and [Ru(dppbz)(pic)2], respectively. The molecular structures of four selected complexes, viz. [Ru(dppbz)(CO)(dmso)Cl2], [Ru(dppbz)2Cl2], [Ru(dppbz)(q)2] and [Ru(dppbz)(pic)2], have been determined by X-ray crystallography. In dichloromethane solution, all the complexes show intense absorptions in the visible and ultraviolet regions. Cyclic voltammetry on the complexes shows redox responses within 0.71 to -1.24 V vs. SCE. [Ru(dppbz)(CO)2Cl2] has been found to serve as an excellent pre-catalyst for catalytic transfer-hydrogenation and Oppenauer oxidation.
- Mukherjee, Aparajita,Bhattacharya, Samaresh
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p. 15617 - 15631
(2021/05/19)
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- (+)-(R)- and (?)-(S)-Perhexiline maleate: Enantioselective synthesis and functional studies on Schistosoma mansoni larval and adult stages
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Schistosomiasis is a neglected tropical disease mainly affecting the poorest tropical and subtropical areas of the world with the impressive number of roughly 200 million infections per year. Schistosomes are blood trematode flukes of the genus Schistosoma causing symptoms in humans and animals. Organ morbidity is caused by the accumulation of parasite eggs and subsequent development of fibrosis. If left untreated, schistosomiasis can result in substantial morbidity and even mortality. Praziquantel (PZQ) is the most effective and widely used compound for the treatment of the disease, in prevention and control programs in the last 30 years. Unfortunately, it has no effect on juvenile immature schistosomes and cannot prevent reinfection or interfere with the schistosome life cycle; moreover drug-resistance represents a serious threat. The search for an alternative or complementary treatment is urgent and drug repurposing could accelerate a solution. The anti-anginal drug perhexiline maleate (PHX) has been previously shown to be effective on larval, juvenile, and adult stages of S. mansoni and to impact egg production in vitro. Since PHX is a racemic mixture of R-(+)- and S-(?)-enantiomers, we designed and realized a stereoselective synthesis of both PHX enantiomers and developed an analytical procedure for the direct quantification of the enantiomeric excess also suitable for semipreparative separation of PHX enantiomers. We next investigated the impact of each enantiomer on viability of newly transformed schistosomula (NTS) and worm pairs of S. mansoni as well as on egg production and vitellarium morphology by in vitro studies. Our results indicate that the R-(+)-PHX is mainly driving the anti-schistosomal activity but that also the S-(?)-PHX possesses a significant activity towards S. mansoni in vitro.
- Campiani, Giuseppe,Gemma, Sandra,Gimmelli, Roberto,Guidi, Alessandra,Prasanth Saraswati, A.,Relitti, Nicola,Ruberti, Giovina,Saccoccia, Fulvio,Sirignano, Carmina,Taglialatela-Scafati, Orazio
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- Influence of Some Factors on the Progress of a New Reaction in the Chemistry of Organoaluminum Compounds
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Abstract: We earlier discovered a new reaction in the chemistry of organoaluminum compounds (OACs), specifically, the formation of O-isobutyl acetals on low-temperature (–70°C) treatment of seven-membered lactones with a double (or more) molar amount of diisobutylaluminum hydride (DIBAH) in methylene chloride. To assess the boundaries for the formation of isobutyl acetals depending on the ring size, we involved in the low-temperature hydride reduction six-, eight-, and thirteen-membered lactones. To determine how the scope of the new reaction depends on the nature of the organoaluminum reagent, we tested triisobutylaluminum (TIBA). To determine how the formation of isobutyl acetals on low-temperature (–70°C) reduction with excess DIBAH in CH2Cl2 depends on whether the starting ester is cyclic or acyclic and, if the former is the case, on the ring size in the ester, we used the acyclic methyl octadecanoate as the starting compound. It was found that the new reaction in the chemistry of AOC with DIBAH as the reducer is characteristic only of seven-membered lactones and atypical of acyclic methyl octadecanoate and ricinoleate (i.e. acids with the carbon chain length more than 6).
- Ishmuratov, G. Yu.,Vydrina, V. A.,Yakovleva, M. P.
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p. 1353 - 1358
(2020/10/02)
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- Lipid nanoparticle formulations of non-viral capsid-free DNA vectors
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Provided herein are lipid nanoparticle formulations that comprise an ionizable lipid and non-viral, capsid-free DNA vectors with covalently-closed ends.
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Paragraph 0350
(2020/09/26)
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- Transiently Thermoresponsive Acetal Polymers for Safe and Effective Administration of Amphotericin B as a Vaccine Adjuvant
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The quest for new potent and safe adjuvants with which to skew and boost the immune response of vaccines against intracellular pathogens and cancer has led to the discovery of a series of small molecules that can activate Toll-like receptors (TLRs). Whereas many small molecule TLR agonists cope with a problematic safety profile, amphotericin B (AmpB), a Food and Drug Administration approved antifungal drug, has recently been discovered to possess TLR-triggering activity. However, its poor aqueous solubility and cytotoxicity at elevated concentrations currently hampers its development as a vaccine adjuvant. We present a new class of transiently thermoresponsive polymers that, in their native state, have a phase-transition temperature below room temperature but gradually transform into fully soluble polymers through acetal hydrolysis at endosomal pH values. RAFT polymerization afforded well-defined block copolymers that self-assemble into micellar nanoparticles and efficiently encapsulate AmpB. Importantly, nanoencapsulation strongly reduced the cytotoxic effect of AmpB but maintained its TLR-triggering capacity. Studies in mice showed that AmpB-loaded nanoparticles can adjuvant an RSV vaccine candidate with almost equal potency as a highly immunogenic oil-in-water benchmark adjuvant.
- Van Herck, Simon,Van Hoecke, Lien,Louage, Benoit,Lybaert, Lien,De Coen, Ruben,Kasmi, Sabah,Esser-Kahn, Aaron P.,David, Sunil A.,Nuhn, Lutz,Schepens, Bert,Saelens, Xavier,De Geest, Bruno G.
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p. 748 - 760
(2017/12/18)
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- PRODUCTION OF 1,5-PENTANEDIOL VIA UPGRADING OF TETRAHYDROFUFURYL ALCOHOL
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A method of making 1,5-pentanediol from tetrahydrofurfural alcohol. The method includes the steps of dehydrating tetrahydrofurfural alcohol (THFA) to dihydropyran (DHP); hydrating at least a portion of the DHP to 2-hydroxy-tetrahydropyran (2-HY-THP) in the absence of homogeneous acid; and hydrogenating at least a portion of the 2-HY-THP to 1,5-pentanediol. The method can be conducted entirely in the absence of noble metal catalysts.
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- Dehydrogenation of 5-hydroxymethylfurfural to diformylfuran in compressed carbon dioxide: An oxidant free approach
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The dehydrogenation of biomass-based 5-hydroxymethylfurfural (HMF) to 2,5-diformylfuran (DFF) was achieved utilizing an activated carbon supported rhodium (Rh/C) catalyst under mild reaction conditions. The developed method successfully afforded complete conversion and the highest selectivity of DFF (>99%) without any additive, conventional hydrogen acceptor and oxidant. The efficiency of the method is achieved by the addition of compressed carbon dioxide (scCO2) and the synergistic effect of scCO2 and Rh/C, where scCO2 plays a pivotal role in accelerating the reaction by removing hydrogen, and consequently shifting the equilibrium to the forward direction. Optimization of different reaction parameters ensures the achievement of high conversion and selectivity. Characterization of the catalyst using different spectroscopic techniques suggests an interaction between the substrate and the catalyst and provides an indication of the possible reaction pathway, thus a mechanism would be outlined. The rate determining step of the reaction was calculated through mechanistic investigations involving theoretical calculations together with experimental analysis. One of the most attractive features of the method developed in this study is the reverse reaction of DFF, which can be achieved in one-pot without the addition of any external hydrogen. This process has successful application to the dehydrogenation of a variety of alcohols with different substituents.
- Chatterjee, Maya,Ishizaka, Takayuki,Chatterjee, Abhijit,Kawanami, Hajime
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p. 1315 - 1326
(2017/08/15)
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- Synthesis method of 2,2-dimethyl-3-hydroxypropionic acid
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The invention discloses a synthesis method of 2,2-dimethyl-3-hydroxypropionic acid. With isobutyraldehyde and formaldehyde as the raw materials, 2,2-dimethyl-3-hydroxypropionic acid is directly prepared through aldol reaction and disproportionation and oxidation reaction, a catalyst composed of aluminium oxide and manganese oxide is added in the aldol reaction, and a catalyst formed by mixing bismuth oxide with aluminium oxide is added in the disproportionation and oxidation reaction; meanwhile, the reaction conditions are optimized, the excessive consumption of sodium hydroxide is lowered, reaction time is shortened, reaction energy consumption is lowered, reaction yield is improved, and high economic benefits are achieved.
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Paragraph 0032; 0033
(2017/03/14)
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- Three-component reductive alkylation of 2-hydroxy-1,4-naphthoquinones with lactols
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Lactols II, obtained by DIBAL reduction of their corresponding lactones I, in equilibrium with their hydroxyaldehyde tautomers III were used in a three-component reductive alkylation with 2-hydroxy-1,4-naphthoquinone to give a series of 3-alkylated 2-hydroxy-1,4-naphthoquinone derivatives IV.
- Kim, Eliana E.,Onyango, Evans O.,Pace, Jennifer R.,Abbot, Timothy M.,Fu, Liangfeng,Gribble, Gordon W.
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supporting information
p. 864 - 867
(2016/02/05)
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- Syntheses and biological evaluation of 1,2,3-triazole and 1,3,4-oxadiazole derivatives of imatinib
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Three novel series of 1,2,3-triazole and 1,3,4-oxadiazole derivatives of imatinib were prepared and evaluated in vitro for their cytostatic effects against a human chronic myeloid leukemia (K562), acute myeloid leukemia (HL60), and human leukemia stem-like cell line (KG1a). The structure-activity relationship was analyzed by determining the inhibitory rate of each imatinib analog. Benzene and piperazine rings were necessary groups in these compounds for maintaining inhibitory activities against the K562 and HL60 cell lines. Introducing a trifluoromethyl group significantly enhanced the potency of the compounds against these two cell lines. Surprisingly, some compounds showed significant inhibitory activities against KG1a cells without inhibiting common leukemia cell lines (K562 and HL60). These findings suggest that these compounds are able to inhibit leukemia stem-like cells.
- Li, Yong-Tao,Wang, Jing-Han,Pan, Cheng-Wen,Meng, Fan-Fei,Chu, Xiao-Qian,Ding, Ya-Hui,Qu, Wen-Zheng,Li, Hui-Ying,Yang, Cheng,Zhang, Quan,Bai, Cui-Gai,Chen, Yue
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p. 1419 - 1427
(2016/02/19)
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- Characterization of a new enzyme oxidizing ω-amino group of aminocarboxyric acid, aminoalcohols and amines from Phialemonium sp. AIU 274
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A new enzyme exhibiting oxidase activity for ω-aminocarboxylic acids, ω-aminoalcohols, monoamines and diamines was found from a newly isolated fungal strain, Phialemonium sp. AIU 274. The enzyme also oxidized aromatic amines, but not l- and d-amino acids. The Vmax/Km value for hexylamine was higher than those for 6-aminoalcohol and 6-aminhexanoic acid in the aliphatic C6 substrates. In the aliphatic amines, the higher Vmax/Km values were obtained by the longer carbon chain amines. Thus, the enzyme catalyzed oxidative deamination of the ω-amino group in a wide variety of the ω-amino compounds and preferred medium- and long-chain substrates. The oxidase with such broad substrate specificity was first reported here. The enzyme contained copper, and the enzyme activity was strongly inhibited by isoniazid, iproniazid and semicarbazide, but not by clorgyline and pargyline. The enzyme was composed of two identical subunits of 75 kDa.
- Isobe, Kimiyasu,Sasaki, Tomoko,Aigami, Yuusuke,Yamada, Miwa,Kishino, Shigenobu,Ogawa, Jun
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- Perspectives on the kinetics of diol oxidation over supported platinum catalysts in aqueous solution
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The catalytic oxidation of a variety of terminal alcohols was performed over Pt/C with 10 bar dioxygen at 343 K in aqueous solvent at low pH. The influences of Pt particle size, carbon support, alcohol structure, and start-up conditions were explored. Although the turnover frequency was not affected by particle size or the carbon support, the structure of the alcohols affected their initial rate of conversion. Both the rate of oxidation of α,ω-diols and selectivity of the diols to the diacids increased with increasing carbon chain length. The rate of 1,6-hexanediol oxidation was independent of dioxygen pressure and the order of reaction with respect to diol concentration depended on the start-up conditions. A kinetic model involving two types of metal sites was proposed to account for the experimental observations.
- Ide, Matthew S.,Davis, Robert J.
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- Kinetics and mechanism of the oxidation of diols by butyltriphenylphosphonium dichromate
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The oxidation of four vicinal, four non-vicinal diols and one of their monoethers by butyltriphenylphosphonium dichromate (BTPPD), in dimethylsulfoxide (DMSO), resulted in the formation of corresponding hydroxyaldehyde as a main product of the oxidation. The reactions are of first order with respect to BTPPD, however, second order dependence is obtained with respect to each the diol and hydrogen ion. The oxidation of [1,1,2,2-2H 4]ethanediol exhibited primary kinetic isotope effect (k H/kD = 6.61 at 298 K). The temperature dependence of the kinetic isotope effect suggested the symmetrical transition state in the rate-determining step. The rate constants of oxidation of four vicinal diols show excellent correlation with Taft's ∑ σ* values with negative reaction constant, ρz.ast;. The rate of oxidation of ethanediol has been determined in nineteen different solvents. An analysis of the solvent effect indicates the importance of the cation-solvating power of the solvents. A suitable mechanism has been postulated involving the formation of chromate ester in a pre-equilibrium.
- Panday, Dinesh,Kothari, Seema
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experimental part
p. 918 - 925
(2011/09/19)
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- Oxidation of some vicinal and non-vicinal diols by tetrakis(pyridine)silver dichromate: A kinetic and mechanistic study
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The kinetics of oxidation of four vicinal, four non-vicinal diols and two of their monoethers by tetrakis(pyridine)-silver dichromate (TPSD) have been studied in dimethylsulphoxide (DMSO). The main product of oxidation is the corresponding hydroxycarbonyl compound. The reaction is first order in TPSD. Michaelis-Menten type of kinetics is observed with respect to the diols. The reaction is catalysed by hydrogen ions. The hydrogen ion dependence has the form : kobs = a + b (H+]. The oxidation of [1,1,2,2- 2H4] ethanediol exhibits a substantial primary kinetic isotope effect (kH/kD = 5.91 at 298 K). The reaction has been studied in nineteen different organic solvents and the solvent effect has been analysed using Taft's and Swain's multiparametric equations. The temperature dependence of the kinetic isotope effect indicates the presence of a symmetrical transition state in the rate-determining step. A suitable mechanism has been proposed.
- Meena,Daiya,Sharma,Banerji,Kotai,Sharma, Vinita
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experimental part
p. 1887 - 1893
(2012/04/04)
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- Oxidation of some vicinal and non-vicinal diols by morpholinium chlorochromate: A kinetic and mechanistic study
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The kinetics of oxidation of four vicinal, four non-vicinal diols and two of their monoethers by morpholinium chlorochromate (MCC) have been studied in dimethylsulphoxide (DMSO). The main product of oxidation is the corresponding hydroxycarbonyl compound. The reaction is first order in MCC and the diols. The reaction is catalysed by hydrogen ions. The hydrogen ion dependence is taking the form : kobs = a + b [H+]. The oxidation of [1,1,2,2-2H4]ethanediol exhibits a substantial primary kinetic isotope effect (kH/kD = 5.82 at 298 K). The reaction has been studied in nineteen different organic solvents and the solvent effect has been analysed using Taft's and Swain's multiparametric equations. The temperature dependence of the kinetic isotope effect indicates the presence of a symmetrical transition state in the rate-determining step. A suitable mechanism has been proposed.
- Barthora,Baghmar,Agarwal,Sharma, Vinita
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experimental part
p. 677 - 683
(2012/04/10)
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- Total syntheses of sterically locked phycocyanobilin derivatives bearing a 15Z-anti or a 15E-anti CD-ring component
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Total syntheses of sterically locked phycocyanobilin derivatives with a 15Z-anti or a 15E-anti CD-ring component were performed toward elucidation of the stereochemistry and function of the chromophore in phytochromes. In the course of the construction of a sterically locked 15E-anti CD-ring component employing 5-tosylpyrrolin-2-one derivatives as the D-ring, the Ts group was found to be rearranged under acidic conditions to give a mixture of regioisomers, both of which could be transformed into the same CD-ring precursor via detosylation with a base followed by Wittig-like coupling reaction. In addition, a sterically locked 15E-anti biliverdin derivative was also synthesized.
- Nishiyama, Kaori,Kamiya, Ayumi,Hammam, Mostafa A.S.,Kinoshita, Hideki,Fujinami, Shuhei,Ukaji, Yutaka,Inomata, Katsuhiko
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experimental part
p. 1309 - 1322
(2011/02/22)
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- HYDROFORMYLATION PROCESS
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A process for the production of 4-hydroxybutyraldehyde is described. The process comprises reacting allyl alcohol with a mixture of carbon monoxide and hydrogen in the presence of a solvent and a catalyst comprising a rhodium complex and a diphosphine. The diphoshine is a trans-1,2-bis(bis(3,4-di-n-alkylphenyl)phosphinomethyl)cyclobutane and/or a 2,3-O-isopropylidene-2,3-dihydroxy-1,4-bis[bis(3,4-di-n-alkylphenyl)phosphino] butane. The process gives high yield of 4-hydroxybutyraldehyde compared to 3-hydroxy-2-methylpropionaldehyde.
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(2010/12/17)
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- Synthesis of fluorogenic polymers for visualizing cellular internalization
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(Chemical Equation Presented) The binding of a polymeric ligand to a cell surface receptor can promote its internalization. Methods to track and visualize multivalent ligands within a cell can give rise to new therapeutic strategies and illuminate signaling processes. We have used the features of the ring-opening metathesis polymerization (ROMP) to develop a general strategy for synthesizing multivalent ligands equipped with a latent fluorophore. The utility of ligands of this type is highlighted by visualizing multivalent antigen internalization in live B cells.
- Mangold, Shane L.,Carpenter, Rachael T.,Kiessling, Laura L.
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supporting information; experimental part
p. 2997 - 3000
(2009/05/07)
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- An expeditious and environmentally benign methodology for the synthesis of substituted indoles from cyclic enol ethers and enol lactones
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A simple and environmentally friendly method is developed for the synthesis of substituted indoles from commercially available aryl hydrazines and cyclic enol ethers with Montmorillonite-K10 as a heterogeneous catalyst. The catalyst is non-toxic, inexpensive and recyclable and the process is clean, high yielding and operationally simple.
- Singh, Pankajkumar R.,Surpur, Mandar P.,Patil, Sachin B.
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p. 3335 - 3340
(2008/09/21)
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- An experimental and computational approach to defining structure/reactivity relationships for intramolecular addition reactions to bicyclic epoxonium ions
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In this manuscript we report that oxidative cleavage reactions can be used to form oxocarbenium ions that react with pendent epoxides to form bicyclic epoxonium ions as an entry to the formation of cyclic oligoether compounds. Bicyclic epoxonium ion structure was shown to have a dramatic impact on the ratio of exo- to endo-cyclization reactions, with bicyclo[4.1.0] intermediates showing a strong preference for endo-closures and bicyclo[3.1.0] intermediates showing a preference for exo-closures. Computational studies on the structures and energetics of the transition states using the B3LYP/6-31G(d) method provide substantial insight into the origins of this selectivity.
- Wan, Shuangyi,Gunaydin, Hakan,Houk,Floreancig, Paul E.
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p. 7915 - 7923
(2008/02/13)
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- Synthesis of beta-L-2'-deoxy nucleosides
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An improved process for the preparation of 2′-modified nucleosides and 2′-deoxy-nucleosides, such as, β-L-2′-deoxy-thymidine (LdT), is provided. In particular, the improved process is directed to the synthesis of a 2′-deoxynucleoside that may utilize different starting materials but that proceeds via a chloro-sugar intermediate or via a 2,2′-anhydro-1-furanosyl-nucleobase intermediate. Where an 2,2′-anhydro-1-furanosyl base intermediate is utilized, a reducing agent, such as Red-Al, and a sequestering agent, such as 15-crown-5 ether, that cause an intramolecular displacement reaction and formation of the desired nucleoside product in good yields are employed. An alternative process of the present invention utilizes a 2,2′-anhydro-1-furanosyl base intermediate without a sequestering agent to afford 2′-deoxynucleosides in good yields. The compounds made according to the present invention may be used as intermediates in the preparation of other nucleoside analogues, or may be used directly as antiviral and/or antineoplastic agents.
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Page/Page column 29
(2010/02/11)
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- Synthesis of biliverdin derivative bearing the sterically fixed E-anti C/D-ring component
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Biliverdin (BV) derivative bearing the E-anti C/D-ring component, which is sterically fixed by 8-membered ring, was synthesized toward investigation of the structure and function of the chromophore in phytochrome. Copyright
- Kinoshita, Hideki,Hammam, Mostafa A. S.,Inomata, Katsuhiko
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p. 800 - 801
(2007/10/03)
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- PROCESS FOR PREPARING HEXAHYDROPYRIMIDO[1,2-A]AZEPINE-2-CARBOXYLATES AND RELATED COMPOUNDS
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Processes for preparing 10-amino-3-hydroxy-4-oxo-4,6,7,8,9,10-hexahydropyrimido[1,2-a]azepine-2-carboxylates and related compounds are disclosed. The preparation of carboxamide derivatives from these carboxylates is also disclosed. The carboxamides are HIV integrase inhibitors and are useful for treating HIV infection and AIDS.
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Page/Page column 62
(2008/06/13)
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- Hydroformylation
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The present invention relates to a process for hydroformylating in the presence of a catalyst comprising at least one complex of a metal of transition group VIII with mono-phosphorus compounds which are capable of dimerizing via noncovalent bonds as ligands, to such catalysts and to their use.
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- Kinetics and mechanism of oxidation of some vicinal and non-vicinal diols by quinolinium bromochromate
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Kinetics of oxidation of four vicinal, four non-vicinal diols and two of their monoethers by quinolinium bromochromate (QBC) have been studied in dimethyl sulphoxide (DMSO). The main product of oxidation is the corresponding hydroxycarbonyl compound. The reaction is first order each in QBC and the diols. The reaction is catalysed by hydrogen ions. The hydrogen ion dependence is taking the form: kobs = a + b[H+]. The oxidation of [1,1,2,2-2H4] ethanediol exhibits a substantial primary kinetic isotope effect (kH/kD = 5.83 at 298 K). The reaction has been studied in nineteen different organic solvents and the solvent effect has been analysed using Taft's and Swain's multiparametric equations. The temperature dependence of the kinetic isotope effect indicates the presence of a symmetrical transition state in the rate-determining step. A suitable mechanism has been proposed.
- Vyas, Shweta,Sharma, Pradeep K.
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p. 1219 - 1223
(2007/10/03)
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- Facile and Chemo-selective Cleavages of Allyl Ethers Utilizing Tetrabutylammonium Sulfate Radical Species
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Allyl ethers containing various functional groups reacted with tetrabutylammonium peroxydisulfate in acetonitrile under mild conditions to afford the corresponding cleaved alcohols in excellent yields.
- Yang, Seung Gak,Park, Min Young,Kim, Yong Hae
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p. 492 - 494
(2007/10/03)
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- Kinetics and mechanism of oxidation of some diols by benzyltrimethylammonium chlorobromate
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Kinetics of oxidation of five vicinal, four non-vicinal diols, and one of their monoethers by benzyltrimethylammonium chlorobromate (BTMACB) have been studied. The vicinal diols yield the products arising out of the glycol-bond fission while the other diols afford the hydroxycarbonyl compounds. The reaction is first order with respect to diols and the BTMACB. The reaction failed to induce the polymerization of acrylonitrile. There is no effect of benzyltrimethylammonium chloride or potassium bromide on the reaction rate. The proposed reactive oxidizing species is chlorobromate ion. The effect of solvent composition indicated that the rate increases with an increase in the polarity of the solvent. The oxidation of [1,1,2,2-2H4]ethanediol show an absence of primary kinetic isotope effect. The value of solvent isotope effect, k(H2O)/k(D2O), at 288 K for the oxidation of ethanediol, propane-1,3-diol and 3-methoxybutan-1-ol are 3.32, 1.04 and 1.01 respectively. A cyclic mechanism involving a glycol-bond fission has been proposed for the oxidation of the vicinal diols. The other diols are oxidised by a hydride-transfer mechanism, as are monohydric alcohols.
- Bhatt, Monica,Sharma, Pradeep K.,Banerji, Kalyan K.
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p. 826 - 831
(2007/10/03)
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- A general synthetic route towards γ- and δ-lactones. Total asymmetric synthesis of (-)-muricatacin and the mosquito oviposition pheromone (5R, 6s)- 6-acetoxy-hexadecanolide
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Five (or six) membered asymmetric lactones are synthesized from γ- butyrolactone (or δ-valerolactone) in a straightforward way using the following reaction sequence: reduction, Wittig-Schlosser coupling, Sharpless asymmetric dihydroxylation, oxidation and lactonization. Thus, (-)muricatacin is synthesized in six steps (43% overall yield). Furthermore, (5R,6S)-6- acetoxy-hexadecanolide is prepared in eight steps (38% overall yield) via a carbonate ester, utilizing a novel lactonization with inversion of stereochemistry.
- Couladourosand, Elias A.,Mihou, Anastasia P.
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p. 4861 - 4862
(2007/10/03)
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- Synthesis of the left hand unit of batzelladine F; revision of the reported relative stereochemistry
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The addition of guanidine to the bis-α,β-unsaturated ketone 17 is reported, leading to the formation of the tricyclic guanidine 18, the left hand portion of the naturally occurring alkaloid batzelladine F. Nmr evidence is given which casts doubt upon the assignment of the relative stereochemistry of this metabolite.
- Black, Gregory P.,Murphy, Patrick J.,Thornhill, Andrew J.,Walshe, Nigel D. A.,Zanetti, Cinzia
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p. 6547 - 6554
(2007/10/03)
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- Kinetics and mechanism of oxidation of diols by quinolinium fluorochromate
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The kinetics of oxidation of four vicinal diols, four non-vicinal diols and two of their monoethers by quinolinium fluorochromate (QFC) have been studied in dimethylsulphoxide. The main product of oxidation is the corresponding hydroxycarbonyl compound. The reaction is first order in QFC. Michaelis-Menten type kinetics have been observed with respect to the diols. The oxidation of [1,1,2,22H4] ethanediol exhibits a substantial primary kinetic isotope effect (k(H)/k(D) = 6.35 at 303 K). The reaction has been in nineteen different organic solvents and the solvent effect has been analysed using Taft's and Swain's multiparametric equation. The temperature dependence of the kinetic isotope effect indicates the presence of a symmetrical transition state in the rate-determining step. A suitable mechanism has been proposed.
- Choudhary, Kirti,Sharma, Pradeep K.,Banerji, Kalyan K.
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p. 325 - 330
(2007/10/03)
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- Kinetics and Mechanism of Oxidation of Diols by Hexamethylenetetramine-bromine
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Kinetics of oxidation of five vicinal, four non-vicinal diols, and one of their monoethers by hexamethylenetetramine-bromine (HABR) have been studied. The vicinal diols yielded the products arising out of the glycol bond fission while the other diols yielded the hydroxycarbonyl compounds. The reaction is first order with respect to HABR. Michaelis-Menten type kinetics were observed with respect to the diol. Addition of hexamethylenetetramine resulted in an increase in the rate of reaction. The oxidation of 2H4>ethanediol showed an absence of primary kinetic isotope effect. A mechanism involving a glycol bond fission has been proposed for the oxidation of the vicinal diols. The other diols are oxidised by a hydride-transfer mechanism as are monohydric alcohols.
- Gangwani, Hemlata,Sharma, Pradeep K.,Banerji, Kalyan K.
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p. 854 - 871
(2007/10/03)
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- Synthesis of 2-phenyl-2-cycloalkenones via palladium-catalyzed tandem epoxide isomerization-intramolecular aldol condensation
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We have extended the scope of our palladium-catalyzed tandem epoxide isomerization/aldol condensation reaction to encompass intramolecular condensations, which provide facile access to conjugated cycloalkenones from epoxy aldehydes or diepoxides. For example, reaction of 5,6-epoxy-6- phenylhexanal with Pd(OAc)2-PBu3 catalyst in the presence of NaHCO3 and 3A molecular sieves forms 2-phenyl-2-cyclopentenone (80%). Similarly, 1,2;5,6-diepoxy-1-phenylhexane affords 3-methyl-2-phenyl-2-cyclopentenone (72%). The observation of dicarbonyl intermediates (e.g., 1-phenyl-2,5- hexanedione in the latter case) demonstrates that the reaction proceeds via Pd-catalyzed isomerization of the diepoxide to the diketone, followed by base-catalyzed aldol condensation.
- Kim, Ji-Hyun,Kulawiec, Robert J.
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p. 3107 - 3110
(2007/10/03)
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- Isoquinolinium dichromate: A new and selective oxidant for primary and secondary alcohols
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Isoquinolinium clichromate is a new versatile reagent for selective oxidation of primary and secondary alcohols under mild conditions. It also oxidises vicinal and nonvicinal diols to the corresponding α-hydroxy carbonyl compounds.
- Srinivasan,Akila,Caroline,Balasubramanian
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p. 2245 - 2251
(2007/10/03)
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- Kinetics and Mechanism of the Oxidation of Diols by Pyridinium Bromochromate
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The kinetics of oxidation of four vicinal diols, four nonvicinal diols, and one of their monoethers by pyridinium bromochromate (PBC) have been studied in dimethyl sulfoxide.The main product of oxidation is the corresponding hydroxyaldehyde.The reaction is first-order with respect to each the diol and PBC.The reaction is acid-catalyzed and the acid dependence has the form: kobs = a + b+>.The oxidation of ethanediol exhibited a primary kinetic isotope effect (kH/kD = 6.70 at 298 K).The reaction has been studied in 19 organic solvents including dimethyl sulfoxide and the solvent effect has been analyzed using multiparametric equations.The temperature dependence of the kinetic isotope effect indicates the presence of a symmetrical transition state in the rate-determining step.A suitable mechanism has been proposed.
- Rao, P. Surya Chandra,Suri, Deepa,Kothari, Seema,Banerji, Kalyan K.
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p. 285 - 290
(2007/10/03)
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- Kinetics and Mechanism of the Oxidation of Diols by 2.2'-Bipyridinium Chlorochromate
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The kinetics of oxidation of four vicinal diols. four non-vicinal diols and two of their monoethers by 2.2'-bipyridinium chlorochromate (BPCC) have been studied in dimethyl sulfoxide.The main product of oxidation is the corresponding hydroxycarbonyl compound.The reaction is first order with respect to both BPCC and the diol.The oxidation of ethanediol exhibits a substantial primary kinetic isotope effect (kN/kD = 6.35 at 303 K).The reaction has been studied in nineteen different organic solvents and the solvent effect has been analysed using Taft's and Swain's multiparametric equations.The temperature dependence of the kinetic isotope effect indicates the presence of a symetrical transition state in the rate-determining step.A suitable mechanism has been proposed.
- Loonker, Kavita,Sharma, Pradeep K.,Banerji, Kalyan K.
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p. 1663 - 1680
(2007/10/03)
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- Kinetics and Mechanism of the Oxidation of Diols by Ethyl N-Chlorocarbamate
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The kinetics of oxidation of five vicinal and four non-vicinal diols, and two of their monoethers by ethyl N-chlorocarbamate (ECC) have been studied.The vicinal diols yielded products arising out of the glycol bond fission while the other diols yielded hydroxycarbonyl compounds.The reaction is first order with respect to ECC, the diol, and hydrogen ions.Addition of ethyl carbamate and acrylonitrile has no effect on the reaction.The oxidation of ethanediol showed the absence of a primary kinetic isotope effect.The values of solvent isotope effect, k(H2O/k(D2O, at 303 K for the oxidation of ethanediol, propane-1,3-diol and 3-methoxybutan-1-ol are 3.51, 2.21, and 1.98 respectively.An acyclic mechanism involving glycol bond fission has been proposed for the oxidation of the vicinal diols.The other diols are oxidized by a hydride-transfer mechanism as are monohydric alcohols.
- Grover, Anjali,Varshney, Seema,Banerji, Kalyan K.
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p. 629 - 632
(2007/10/02)
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- THE BIOCHEMICAL BASIS FOR THE DELETERIOUS EFFECTS OF L-CANAVANINE
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L-Cavanine, L-2-amino-4-(guanidinooxy)butyric acid, is a potentially toxic analogue of L-arginine.Canavanine-sensitive organism activate and aminoacylate this non-protein amino acid and thereby create structurally aberrant, canavanine-containing proteins.Incorporation of canavanine into protein can alter the conformation and disrupt the function of the native macromolecule.Production of functionally impaired, canavanyl proteins affects developmental processes and contributes significantly to the expression of canavanine's potent antimetabolic properties in insects.Key Word Index: Canavalia ensiformis; Leguminosae; L-canavanine; non-protein amino acid; toxicity; canavanyl proteins; insects.
- Rosenthal, Gerald A.
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p. 1055 - 1058
(2007/10/02)
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- REINVESTIGATION OF THE HYDRATION OF 3,4-DIHYDRO-2H-PYRAN
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Hydration of 3,4-dihydro-2H-pyran (1) gave 5-hydroxypentanal (3), its lactl-form (2) and the THP-protected compounds (4 and 5) of 2 and 3.The dependence of formation of the four products (2, 3, 4 and 5) on the reaction conditions was investigated.
- Vinczer, Peter,Juvancz, Zoltan,Novak, Lajos,Szantay, Csaba
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p. 581 - 585
(2007/10/02)
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- Meerwein-Ponndorf-Verley-Type Reduction of Dicarbonyl Compounds to Hydroxy Carbonyl Compounds and α,β-Unsaturated Carbonyl Compounds to Allylic Alcohols Catalyzed by Zirconocene and Hafnocene Complexes
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Group IVA metallocene complexes such as bis(η5-cyclopentadienyl)zirconium dihydrides, Cp2ZrH2 (1), and hafnium dihydrides, Cp2HfH2 (8), catalyze the chemoselective reduction of polycarbonyl compounds to hydroxy carbonyl compounds.For instance, the reduction of keto aldehydes 3-ketobutanal (2g) and 2-phenyl-2-ketoethanal (2h) proceeded selectively at aldehyde group to provide the corresponding hydroxy ketones 3g and 3h in 91percent and 93percent yields, respectively.Under similar conditions, however, cyclohexanediones were easily aromatized to benzenediols.On the other hand, 1 and 8 also catalyze the selective 1,2-reduction of various types of α,β-unsaturated carbonyl compounds, giving the corresponding allylic alcohols in good to excellent yields.Thus, steroidal dicarbonyl compounds, having an enone framework in their molecules Δ4-androstene-3,17-dione (11a) and Δ4-progestene-3,20-dione (11b) were reduced by 1 to 17-hydroxy-Δ4-androsten-3-one (12a) and 20-hydroxy-Δ4-progest-3-one (12b), which are essential human hormones, in 80percent and 67percent yields, respectively.
- Nakano, Tatsuya,Umano, Shigetoshi,Kino, Yoshio,Ishii, Yasutaka,Ogawa, Masaya
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p. 3752 - 3757
(2007/10/02)
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- SYNTHESIS OF PHEROMONES, IV. CHEMISTRY OF THE WITTIG REACTION, I. EFFECTS OF REACTION CONDITIONS ON THE STEREOSELECTIVITY AND YIELD OF THE WITTIG REACTION
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The reactions of nonstabilized triphenylphosphorus ylides with aldehydes have been studied in detail.The stereochemistry and yields of the alkene products are highly dependent upon base used for the generation of the ylide, the solvent and reaction temperature.The synthesis of sex pheromone components by Wittig reaction are also described.
- Vinczer, Peter,Juvancz, Zoltan,Novak, Lajos,Szantay, Csaba
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p. 797 - 820
(2007/10/02)
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- Investigation of the Dynamic Behavior of Sugar Model Compounds by Nuclear Magnetic Resonance
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Rate constants for the tautomeric equilibrium of 5-hydroxypentanal, a model compound for aldopyranose, have been determined by line-shape analysis of the 13C-NMR spectrum obtained from an acidified solution in water.
- Buddrus, Joachim,Jablonowski, Maria,Brinkmeier, Arno
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p. 547 - 548
(2007/10/02)
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- Kinetic Study of Oxidation of Diols by Sodium N-Bromobenzenesulphonamide
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The kinetics of the oxidation of five vicinal diols, four other diols, and one of their monoethers by sodium N-bromobenzenesulphonamide have been studied.The vicinal diols yielded products arising out of glycol bond fission while other diols yielded hydroxycarbonyl compounds.The reaction is first order with respect to the diol and the oxidant.The oxidation of vicinal diols follows two mechanistic pathways, one acid-independent and the another acid-dependent.The oxidation of the other diols shows a first-order dependence on hydrogen ion.The oxidation of ethanediol showed the absence of a primary kinetic isotope effect.The values of solvent isotope effect, k(H2O)/k(D2O), at 303 K for the oxidation of ethanediol, propane-1,3-diol, and 3-methoxybutan-1-ol are 2,24, 0.42. and 0.42, respectively.An acyclic mechanism involving glycol bond fission has been proposed for the vicinal diols.The other diols are oxidized by a hydride-transfer mechanism as are monohydric alcohols.
- Mathur, Abha,Banerji, Kalyan K.
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p. 1645 - 1648
(2007/10/02)
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- Chemoselective Oxidation of the Primary Alcohol Function of Diols Catalyzed by Zirconocene Complexes
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Zirconocene complexes, Cp2ZrH2 and Cp2Zr2, catalyze the Oppenauer-type oxidation of alcohol functions to the corresponding carbonyl compounds in the presence of an appropriate hydrogen acceptor such as benzophenone.In the oxidation of primary α,ω-diols and of diols containing two secondary alcohol functions, one of the alcohol functions is selectively oxidized to form hydroxy aldehydes and hydroxy ketones, respectively, in substantial yields.The chemoselective oxidation of the primary alcohol function can be achieved in the oxidation of diols containing both the primary and secondary alcohol functions.
- Nakano, Tatsuya,Terada, Takanobu,Ishii, Yasutaka,Ogawa, Masaya
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p. 774 - 776
(2007/10/02)
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- Kinetics and mechanism of the oxidation of butane-1,4- and pentane-1,5-diols by 12-tungstocobaltate(III) anion in perchlorate solution
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The kinetics of the oxidation of butane 1,4- and pentane 1,5-diols by the 12-tungstocobaltate(III) anion have been investigated in aqueous perchloric acid at constant ionic strength I=2.00 mol.dm-3 (NaClO4).Although the rate of oxidation of butane 1,4-diol is acid independent that of pentane 1,5-diol increases with increasing acidity and is found to correlate well with Bunnett's relations over the acid concentration range used (0.75-1.75 mol.dm-3).Similarly, the rate is found to be first-order with respect to butane 1,4-diol while it has a second-order dependence on the concentration of pentane 1,5-diol.The observed differences in the behaviour of the two substrates are discussed in terms of inner-sphere mechanism.
- Olatunji, Mobolanle Adegboyega,Ayoko, Godwin Adefikayo
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p. 705 - 708
(2007/10/02)
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- Cyclopentylperoxyl and Cyclohexylperoxyl Radicals in Aqueous Solution: A Study by Product Analysis and Pulse Radiolysis
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Radiolysis of N2O/O2 (4:1 v/v) saturated aqueous solutions of cyclopentane generates cyclopentylperoxyl radicals which decay by a second-order rate process (2k = 1.5*107 M-1s-1) and give rise to the following products (G values in parentheses): cyclopentanone (1.7), cyclopentanol (0.8), glutaraldehyde (1.2), 5-hydroxypentanal (0.8), organic peroxidic material (0.5), and H2O2 (1.7); oxygen is consumed with G=5.0.The corresponding data for cyclohexane solutions are as follows (2k = 1.2*107 M-1s-1): cyclohexanone (2.5), cyclohexanol (0.9), total aldehydes (0.8), organic peroxidic material (0.9), H2O2 (1.6), and oxygen uptake (4.0).During the bimolecular decay of the cycloalkylperoxyl radicals small amounts (G ca. 0.5) of HO2. (H+ + O2-. are formed.It is proposed that in the rate-determining step a short-lived tetroxide is formed which breaks up by four main routes: (i) O2, cycloalkanol, and cycloalkanone, (ii) H2O2 and two molecules of cycloalkanone, (iii) O2 and two ο-formylalkyl radicals (from which the acyclic aldehydes are formed), and (iv) O2 and two cycloalkoxyl radicals.The cycloalkoxyl radicals undergo a 1,2-H shift, a reaction which eventually leads to the formation of the intermediate O2-..In the cyclopentane system the fragmentation (mainly the concerted process iii) is the most important single process (40 percent) whereas in the cyclohexane system this route does not exceed 15 percent.A fragmentation of the acyclic radicals is not observed.
- Zegota, Henryk,Schuchmann, Man Nien,von Sonntag, Clemens
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p. 5589 - 5593
(2007/10/02)
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- Kinetics and Mechanism of Oxidation of Diols by Ceric Ammonium Nitrate in Nitric Acid
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The oxidation of a number of diols by ceric ammonium nitrate in 2M nitric acid is a first order reaction in 0, and a Michaelis-Menten type of correlation between kobs-1 and -1 is noted.However, the observed pseudo-first order rate constant (kobs) increases with decreasing 0 in the oxidation of each substrate.It is noted that the plots between kobs and m>-1 are linear in the oxidation of propane-1,3-, butane-1,4- and butane-1,3-diols, whereas the plots between kobs-1 and m> are linear in the oxidation of pentane-1,5-, hexane-1,6-, heptane-1,7-, octane-1,8-diols and 3-methoxybutanol-1, where Ce(IV)m is a monomeric cerium(IV) species.Based on these two different correlations and other factors, it is proposed that propane-1,3-, butane-1,3- and butane-1,4-diols are oxidised mainly by dimeric cerium(IV) species whereas the rest of the diols and 3-methoxybutanol-1 are oxidised by monomeric cerium(IV).The mechanism and the observed thermodynamic parameters are discussed.
- Nagori, Ratan Raj,Mehta, Mahendra,Mehrotra, Raj Naraian
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