- New technology for synthesizing 1,3-propylene glycol from glycerin through dehydroxylation method
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The invention discloses a new technology for synthesizing 1,3-propylene glycol from glycerin through a dehydroxylation method. The technology comprises the following steps: protecting two hydroxyl groups at the head end and the tail end of a glycerin molecule through using a group protection process, converting a hydroxyl group in the middle of the molecule into a group easy to eliminate, that is a sulfonyloxy group, removing hydroxyl group protection groups, and reducing the sulfonyloxy in the presence of a catalyst in order to obtain the 1,3-propylene glycol product. The technology has the characteristics of few byproducts, easiness in separation, and low cost, is a route with environmentally-friendly and economic dual values, and has wide development prospect.
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Paragraph 0017; 0018
(2017/05/12)
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- Synthesis and biological evaluation of enantiomerically pure glyceric acid derivatives as LpxC inhibitors
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Inhibitors of the UDP-3-O-[(R)-3-hydroxymyristoyl]-N-acetylglucosamine deacetylase (LpxC) represent a promising class of novel antibiotics, selectively combating Gram-negative bacteria. In order to elucidate the impact of the hydroxymethyl groups of diol (S,S)-4 on the inhibitory activity against LpxC, glyceric acid ethers (R)-7a, (S)-7a, (R)-7b, and (S)-7b, lacking the hydroxymethyl group in benzylic position, were synthesized. The compounds were obtained in enantiomerically pure form by a chiral pool synthesis and a lipase-catalyzed enantioselective desymmetrization, respectively. The enantiomeric hydroxamic acids (R)-7b (Ki = 230 nM) and (S)-7b (Ki = 390 nM) show promising enzyme inhibition. However, their inhibitory activities do not substantially differ from each other leading to a low eudismic ratio. Generally, the synthesized glyceric acid derivatives 7 show antibacterial activities against two Escherichia coli strains exceeding the ones of their respective regioisomes 6.
- Tangherlini, Giovanni,Torregrossa, Tullio,Agoglitta, Oriana,K?hler, Jens,Melesina, Jelena,Sippl, Wolfgang,Holl, Ralph
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p. 1032 - 1044
(2016/02/19)
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- Conversion of platform chemical glycerol to cyclic acetals promoted by acidic ionic liquids
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The condensation of glycerol, a platform chemical from renewable materials, with benzaldehyde to generate cyclic acetals was investigated using acidic ionic liquid as catalyst. Evidence was presented that the product mixture of 4-hydroxymethyl-2-phenyl-1,3-dioxolane and 5-hydroxyl-2-phenyl-1,3-dioxane, with cis and trans two stereo-isomers for each one identified by 1H NMR were obtained. Further modification of reaction conditions promoted by N-butyl-pyridinium bisulfate ([BPy]HSO4) led to the totally cyclic acetals with 99.8% yield at room temperature. A micro water-removal reactor constituted by ionic liquids was proposed, which favourably shifted the condensation equilibrium to the product side by transferring the produced water out of the organic phase in time, so that the water-carrying agent or reactive distillation was avoided. Moreover, the product separation made this methodology more accessible to sustainable green biomass chemistry.
- Wang, Bo,Shen, Yue,Sun, Jiankui,Xu, Feng,Sun, Runcang
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p. 18917 - 18923
(2014/05/20)
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- Stereocontrol by quaternary centres: A stereoselective synthesis of (-)-luminacin D
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Very high diastereoselectivity can be achieved by 1,3-chelation-controlled allylation of aldehydes that possess a non-chelating α-ether substituent, even if the α-position is a quaternary centre and/or a spiro-epoxide. This reaction was used as a key step in an enantioselective synthesis of the angiogenesis inhibitor luminacin D.
- Bartlett, Nathan,Gross, Leona,Peron, Florent,Asby, Daniel J.,Selby, Matthew D.,Tavassoli, Ali,Linclau, Bruno
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supporting information
p. 3306 - 3310
(2014/04/03)
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- One-step synthesis of solid sulfonic acid catalyst and its application in the acetalization of glycerol: Crystal structure of cis-5-hydroxy-2-phenyl-1,3- dioxane trimer
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A one-pot method was employed to immobilize sulfonic acid onto silica obtained from rice husk ash using 3-(mercaptopropyl)trimethoxysilane to form a solid catalyst denoted as RHASO3H. BET measurements of the catalyst showed the surface area to be 340 m2 g-1 with the average pore volume of 0.24 mL g-1 and the pore diameter of 2.9 nm. Acidity test of cation exchange capacity and pyridine adsorption studies revealed the presence of Bronsted acid sites on the catalyst surface. The catalyst was used in the acetalization reaction of glycerol with benzaldehyde. Under optimized conditions, the reaction showed the maximum conversion of 78 % after 8 h with 67 % selectivity towards the five membered ring isomer. Variation in the glycerol concentration had a significant effect on the reactants conversion. A single crystal X-ray study of one of the products proved the existence of a unique trimer formed by hydrogen bonding by the six-membered cis-isomer. The catalyst was several times recycled without any loss of its catalytic activity.
- Adam, Farook,Batagarawa, Muazu Samaila,Hello, Kasim Mohammed,Al-Juaid, Salih S.
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p. 1048 - 1058
(2013/08/23)
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- Indium(III) triflate catalysed transacetalisation reactions of diols and triols under solvent-free conditions
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Acyclic acetals and ketals undergo transacetalisation in the presence of catalytic quantities of indium(III) triflate (In(OTf)3) and diols or triols under solvent-free conditions to generate the corresponding cyclic acetals and ketals in excellent yield. The methodology has been further developed to encompass a tandem acetalisation-acetal exchange protocol, which provides a facile and high yielding route to cyclic ketals from unreactive ketones under very mild reaction conditions.
- Smith, Brendan M.,Kubczyk, Tomasz M.,Graham, Andrew E.
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p. 7775 - 7781
(2012/09/21)
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- Anionic amphiphilic dendrimers as antibacterial agents
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An anionic amphiphilic dendrimer is reported that possesses increased cytotoxicological potency against prokaryotic cells compared to eukaryotic cells. The half-maximal effective concentration (EC50) for the dendrimer against Bacillus subtilis, a Gram-positive bacterial strain, was measured to be 4.1 × 10-5 M, while that against human umbilical vein endothelial cells (HUVEC) was more than 36× greater at a value of 1.5 × 10-3 M. EC50 ratios for two commercial amphiphiles, sodium dodecyl sulfate (SDS) and Triton X-100, in addition to a similar synthesized dendritic structure were at most only 3.8× greater. Furthermore, the observed EC50 values appear to be correlated to the critical aggregation constant (CAC) in solution suggesting a mechanism of action for these anionic amphiphilic dendrimers related to their supramolecular structures. Copyright
- Meyers, Steven R.,Juhn, Frank S.,Griset, Aaron P.,Luman, Nathanael R.,Grinstaff, Mark W.
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supporting information; body text
p. 14444 - 14445
(2009/02/08)
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- Simultaneous interaction with base and phosphate moieties modulates the phosphodiester cleavage of dinucleoside 3′,5′-monophosphates by dinuclear Zn2+complexes of Di(azacrown) ligands
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Five dinucleating ligands (1-5) and one trinucleating ligand (6) incorporating 1,5,9-triazacyclododecan-3-yloxy groups attached to an aromatic scaffold have been synthesized. The ability of the Zn2+ complexes of these ligands to promote the transesterification of dinucleoside 3′,5′-monophosphates to a 2′,3′-cyclic phosphate derived from the 3′-linked nucleoside by release of the 5′-linked nucleoside has been studied over a narrow pH range, from pH 5.8 to 7.2, at 90 °C. The dinuclear complexes show marked base moiety selectivity. Among the four dinucleotide 3′,5′-phosphates studied, viz. adenylyl-3′,5′-adenosine (ApA), adenylyl-3′,5′-uridine (ApU), uridylyl-3′,5′-adenosine (UpA), and uridylyl-3′, 5′-uridine (UpU), the dimers containing one uracil base (ApU and UpA) are cleaved up to 2 orders of magnitude more readily than those containing either two uracil bases (UpU) or two adenine bases (ApA). The trinuclear complex (6), however, cleaves UpU as readily as ApU and UpA, while the cleavage of ApA remains slow. UV spectrophotometric and 1H NMR spectroscopic studies with one of the dinucleating ligands (3) verify binding to the bases of UpU and ApU at less than millimolar concentrations, while no interaction with the base moieties of ApA is observed. With ApU and UpA, one of the Zn2+- azacrown moieties in all likelihood anchors the cleaving agent to the uracil base of the substrate, while the other azacrown moiety serves as a catalyst for the phosphodiester transesterification. With UpU, two azacrown moieties are engaged in the base moiety binding. The catalytic activity is, hence, lost, but it can be restored by addition of a third azacrown group on the cleaving agent.
- Wang, Qi,Loennberg, Harri
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p. 10716 - 10728
(2007/10/03)
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- Binding of tetramethylammonium to polyether side-chained aromatic hosts. Evaluation of the binding contribution from ether oxygen donors
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A set of macrocyclic and open-chain aromatic ligands endowed with polyether side chains has been prepared to assess the contribution of ether oxygen donors to the binding of tetramethylammonium (TMA), a cation believed incapable of interacting with oxygen donors. The open-chain hosts consisted of an aromatic binding site and side chains possessing a variable number of ether oxygen donors; the macrocyclic ligands were based on the structure of a previously investigated host, the dimeric cyclophane 1,4-xylylene-1,4-phenylene diacetate (DXPDA), implemented with polyether-type side chains in the backbone. Association to tetramethylammonium picrate (TMAP) was measured in CDCl 3 at T = 296 K by 1H NMR titrations. Results confirm that the main contribution to the binding of TMA comes from the cation - π interaction established with the aromatic binding sites, but they unequivocally show that polyether chains participate with cooperative contributions, although of markedly smaller entity. Water is also bound, but the two guests interact with aromatic rings and oxygen donors in an essentially noncompetitive way. An improved procedure for the preparation of cyclophanic tetraester derivatives has been developed that conveniently recycles the oligomeric ester byproducts formed in the one-pot cyclization reaction. An alternative entry to benzylic diketones has also been provided that makes use of a low-order cyanocuprate reagent to prepare in fair yields a class of compounds otherwise uneasily accessible.
- Bartoli, Sandra,De Nicola, Gina,Roelens, Stefano
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p. 8149 - 8156
(2007/10/03)
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- Reactions of 4-chloromethyl-1,3,2-dioxathiolane 2-oxides with sodium phenoxide. A reinvestigation
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The reactions of 4-chloromethyl-1,3,2-dioxathiolane 2-oxides with PhONa in EtOH are accompanied by ring opening under the action of the ethoxide ion rather than leading to a rearrangement of the starting molecule as has been assumed previously. Under conditions precluding competition with other nucleophiles, the phenoxide anion smoothly replaces the chlorine atom in chloromethyl-substituted cyclic sulfites.
- Bredikhina, Z. A.,Pashagin, A. V.,Bredikhin, A. A.
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p. 1753 - 1756
(2007/10/03)
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- Synthesis and lipase-catalyzed enantiotope selective acetylation of 2- benzoyloxy-1,3-propanediol
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Preparation and porcine pancreatic lipase (PPL)-catalyzed enantiotope selective acetylation of the prochiral 2-benzoyloxy-1,3-propanediol (1a) is described. The reaction with PPL and vinyl acetate gave monoacetate (2a) of 96 % e.e.
- Bódai, Viktória,Novák, Lajos,Poppe, László
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p. 759 - 761
(2007/10/03)
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- Stereoselective synthesis of substituted 5-hydroxy-1,3-dioxanes
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A series of 5-hydroxy-1,3-dioxanes has been synthesized using a practical three-step strategy beginning with acetal/ketal formation of tris(hydroxymethyl)aminomethane followed by oxidative cleavage of the amino alcohol. After the ketone was revealed, stereoselective reduction with common hydride reagents, LiAlH4 for the trans isomers and L-Selectride for the cis analogues, gave the target compounds in high yield.
- Forbes, David C.,Ene, Doina G.,Doyle, Michael P.
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p. 879 - 882
(2007/10/03)
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- Conformational Analysis of 5-Substituted 1,3-Dioxanes. 7. Effect of Lithium Bromide Addition
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The position of equilibria, established by means of BF3, between diastereomeric cis- and trans-5- substituted-2-phenyl-1,3-dioxanes, in solvents THF and CHCl3, and in the presence of 0, 1, and 10 equiv of LiBr has been determined. The observed ΔG° values show that the addition of salt to the reaction medium influences the position of equilibrium. Lithium bromide effects on the conformational behavior are discussed in terms of lithium ion complexation events that lead to increased stability of the axial isomers when the substituent at C(5) is CO2H, CO2CH3, CONHCH3, and CH2- OH. By contrast, disruption of the intramolecular hydrogen bond present in the axial 5-acetamido derivative (cis-9 substituent equal to NHCOCH3) modifies the preference for the axial conformation in salt-free 9 to a net dominance of the equatorial isomer in the presence of LiBr. Interpretation of the experimental observations was based on models that are apparently supported by semiempirical AM1 calculations. The results derived from the present study contribute to our understanding of the processes involved in molecular recognition and may model salt effects in physiological events.
- Juaristi, Eusebio,Díaz, Francisco,Cuéllar, Geiser,Jiménez-Vázquez, Hugo A.
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p. 4029 - 4035
(2007/10/03)
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- Origin of the "β-oxygen effect" in the Barton deoxygenation reaction
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Photolysis of O-neopentyl S-tributylstannyl dithiocarbonate with hexaphenyl distannane, and 4-methoxyacetophenone as sensitizer, results in crossover of the stannyl groups. The reaction of O-octyl O′-(2-butoxyethyl) thiocarbonate with tributyltin deuteride or tris(trimethylsilyl)silane and a radical initiator shows no significant preference for the cleavage of either C-O bond. Intermolecular competitions between O-octyl O′-phenyl thiocarbonate and O-(2-butoxyethyl) O′-phenyl thiocarbonate for a deficiency of stannane or silane also indicated no significant preference for reaction of the β-oxygen-substituted substrate, leading to the conclusion that in conformationally unrestricted systems there is no significant β-oxygen effect in the Barton deoxygenation reaction. Competition experiments between the cis- and trans-O-(4-phenylcyclohexyl) S-methyl dithiocarbonates and the cis- and trans-O-(2-phenyl1,3-dioxan-5-yl) S-methyl dithiocarbonates for reaction with tributylstannane reveal that in every case the heterocyclic system is more reactive. The cis-isomers of 4-phenylcyclohexyl S-methyl dithiocarbonate and O-(2-phenyl-1,3-dioxan-5-yl) 5-methyl dithiocarbonate, with their axial xanthates, are more reactive than the corresponding transisomers. Molecular mechanics calculations suggest that the greater reactivity of the cis-series with respect to the trans is due to the greater relief of strain on fragmentation.
- Crich, David,Beckwith, Athelstan L. J.,Chen, Chen,Yao, Qingwei,Davison, Ian G. E.,Longmore, Robert W.,De Parrodi, Cecilia Anaya,Quintero-Cortes, Leticia,Sandoval-Ramirez, Jésus
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p. 8757 - 8768
(2007/10/02)
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- 1,3-Dioxan-5-ones: synthesis, deprotonation, and reactions of their lithium enolates
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A general synthetic route to 2-alkyl- and 2,2-dialkyl-1,3-dioxan-5-ones, using tris(hydroxymethyl)nitromethane as the starting material, is described.Deprotonation of these compounds was studied.It was established that these dioxanones could be deprotonated with LDA; however, the reduction of the carbonyl group via a hydride transfer from LDA, giving the corresponding dioxanols, often competed with deprotonation.The reduction could be minimized by using Corey's internal quench procedure to form silyl enol ethers and was less pronounced in 2,2-dialkyldioxanones (ketals) than in 2-alkyldioxanones (acetals).Self-aldol products were observed when dioxanone lithium enolates were quenched with H2O.Addition reactions of lithium enolates of dioxanones to aldehydes were threo-selective as predicted by the Zimmerman-Traxler model.Dioxanones having two different alkyl groups at the 2-position were deprotonated enantioselectively by chiral lithium amide bases with enantiomeric excess (ee) of up to 70percent. - Key words: 1,3-dioxan-5-ones, enantioselective deprotonation, chiral lithium amides.
- Majewski, Marek,Gleave, D. Mark,Nowak, Pawel
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p. 1616 - 1626
(2007/10/02)
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- Thio-sugars. Part 6. Seco-nucleosides related to 4-thio-DL-erythrofuranose and 4-thio-DL-ribofuranose.
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The thio-sugar synthesis has been adapted to prepare seco-nucleosides, so named by analogy with steroids, for comparison with antiviral agents such as acycloguanosine.Bis(β-hydroxyethyl) sulphoxide gave, via a triacetate, crystalline 4'-thio-2',3'-seco-3'-norcytidine and similar nucleosides - also obtainable by successive action of NaIO4 and NaBH4 on the corresponding (much less soluble) 4-thioerythrosides.In unsymmetrical methyl sulphoxides, the presence of β-OH groups tends to reverse the direction of normal Pummerer rearrangement and both 1',2'-seco-2'-nor and 2',3'-dinoruridines were thus inaccessible: the latter have the acycloguanosine type side-chain.However, 2',3'-seco-3',5'-dinoruridines were readily isolated and in turn yielded 2,2'-but not 2',6-cyclonucleosides.The scope of these uridine cyclisations is briefly reviewed.
- McCormick, Joan E.,McElhinney, R. Stanley
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p. 256 - 281
(2007/10/02)
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