- Selective Monoacylation of Diols and Asymmetric Desymmetrization of Dialkyl meso-Tartrates Using 2-Pyridyl Esters as Acylating Agents and Metal Carboxylates as Catalysts
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With 2-pyridyl benzoates as acylating agents and Zn(OAc)2 as a catalyst, 1,2-diols, 1,3-diols, and catechol were selectively monoacylated. Furthermore, the highly enantioselective desymmetrization of meso-tartrates was achieved for the first time, utilizing 2-pyridyl esters and NiBr2/AgOPiv/Ph-BOX in CH3CN or CuCl2/AgOPiv/Ph-BOX in EtOAc catalyst systems (up to 96% ee). The latter catalyst system was also effective for the kinetic resolution of dibenzyl dl-tartrate.
- Hashimoto, Yuki,Michimuko, Chiaki,Yamaguchi, Koki,Nakajima, Makoto,Sugiura, Masaharu
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p. 9313 - 9321
(2019/08/12)
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- New pH-responsive gemini lipid derived co-liposomes for efficacious doxorubicin delivery to drug resistant cancer cells
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A gemini version of the amphiphile palmitoyl homocysteine was synthesized. Co-liposomes were prepared using the gemini along with a natural zwitterionic lipid, DOPE and cholesterol at specified ratios. This afforded pH-responsive co-liposomes which could efficiently transport the anticancer drug, doxorubicin (DOX), across the DOX-resistant HeLa cancer cells in response to low pH of cellular endosomes.
- Moitra, Parikshit,Kumar, Krishan,Sarkar, Sourav,Kondaiah, Paturu,Duan, Wei,Bhattacharya, Santanu
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supporting information
p. 8184 - 8187
(2017/07/24)
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- Hydrogen Bonding-Assisted Enhancement of the Reaction Rate and Selectivity in the Kinetic Resolution of d,l-1,2-Diols with Chiral Nucleophilic Catalysts
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An extremely efficient acylative kinetic resolution of d,l-1,2-diols in the presence of only 0.5 mol% of binaphthyl-based chiral N,N-4-dimethylaminopyridine was developed (selectivity factor of up to 180). Several key experiments revealed that hydrogen bonding between the tert-alcohol unit(s) of the catalyst and the 1,2-diol unit of the substrate is critical for accelerating the rate of monoacylation and achieving high enantioselectivity. This catalytic system can be applied to a wide range of substrates involving racemic acyclic and cyclic 1,2-diols with high selectivity factors. The kinetic resolution of d,l-hydrobenzoin and trans-1,2-cyclohexanediol on a multigram scale (10 g) also proceeded with high selectivity and under moderate reaction conditions: (i) very low catalyst loading (0.1 mol%); (ii) an easily achievable low reaction temperature (0 °C); (iii) high substrate concentration (1.0 M); and (iv) short reaction time (30 min). (Figure presented.).
- Fujii, Kazuki,Mitsudo, Koichi,Mandai, Hiroki,Suga, Seiji
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supporting information
p. 2778 - 2788
(2017/08/23)
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- The catalytic synthesis of carboniolamide: The role of sp 3 hybridized oxygen
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A catalytic synthesis of carboniolamide has been reported. The strategy was straightforward with aldehyde and amide as starting materials. The products can be isolated as precipitates from the reaction mixture. The factor that stabilizes the labile functionality of hemiaminal was elucidated as a sp 3 hybridized oxygen.
- Zhang, Yi,Dai, Yuchi,Li, Guigen,Cheng, Xu
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supporting information
p. 2644 - 2648
(2015/02/02)
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- The catalytic synthesis of carboniolamide: The role of sp 3 hybridized oxygen
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A catalytic synthesis of carboniolamide has been reported. The strategy was straightforward with aldehyde and amide as starting materials. The products can be isolated as precipitates from the reaction mixture. The factor that stabilizes the labile functionality of hemiaminal was elucidated as a sp 3 hybridized oxygen.
- Zhang, Yi,Dai, Yuchi,Li, Guigen,Cheng, Xu
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supporting information
(2015/08/06)
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- The discovery of a facile access to the synthesis of NSAID dendritic prodrugs
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An efficient and straightforward method for the preparation of dendritic prodrugs is reported. Based on this new approach, a class of biodegradable dendrimers has been synthesised from L-tartaric acid and one of the nonsteroidal anti-inflammatory drugs, namely, aspirin or ibuprofen Tianjin Key Laboratory for Modern Drug Delivery and High-Efficiency, School of Pharmaceutical Science and Technology, Tianjin Universit ,Tianjin 300072, P. R. China.
- Du, Zuyin,Lu, Yanhui,Dai, Xuedong,Negrerie, Daisy Zhang,Gao, Qingzhi
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p. 177 - 180
(2013/07/05)
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- SATURATED FUSED [1,2-B] PYRIDAZINONE COMPOUNDS
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The invention is directed to saturated fused [1,2-b]pyridazinone compounds and pharmaceutical compositions containing such compounds that are useful in treating infections by hepatitis C virus.
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Page/Page column 83-84
(2008/12/06)
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- 2-Chloro-(4R,5R)-bis[(1R,2S,5R)-menth-1-yloxycarbonyl]-1,3, 2-dioxaphospholane: A practical chiral pool-derived reagent for determining enantiomeric purity of alcohols
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(Chemical Equation Presented) 2-Chloro-(4R,5R)-bis[(1R,2S,5R)-menth-1- yloxycarbonyl)]-1,3,2-dioxaphospholane is a practical reagent for reliably determining enantiomeric purity of chiral alcohols via 31P NMR spectroscopy. The compound is available as a crystalline solid on a 20 g scale from PCl3 and bis[(1R,2S,5R)-menth-1-yl] tartrate. It is comparatively inert toward spontaneous hydrolysis under conventional laboratory conditions but undergoes quantitative substitution of alkoxide for chloride if treated with a chiral alcohol. Nonequivalent 31P NMR signals of diastereomeric 2-alkoxy-1,3,2-dioxophospholanes were dispersed by ～1.4-0.1 ppm. The associated integral ratios reflected enantiomeric purities of preweighted samples of (R)- and (S)-1-phenylethanol, (+)- and (-)-menthol, and a set of primary, secondary, and tertiary alcohols with a precision of ±0.4-1.0%.
- Amberg, Matthias,Bergstraesser, Uwe,Stapf, Georg,Hartung, Jens
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p. 3907 - 3910
(2008/09/20)
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- Synthesis and chiroptical properties of a new type of chiral depsipeptide dendrons
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A new type of chiral depsipeptide dendrons based on tartaric acid as branching juncture and ω-aminocapronic acid as spacer has been prepared. Natural and unnatural tartaric acid building blocks have been incorporated, providing access to combinatorial libraries. All compounds have been completely characterized by FAB-MS, EA analysis, 1H/13C NMR- and UV/Vis-spectroscopy. 1H NMR relaxation measurements have been used to examine the conformational flexibility of these dendrons in CH3CN and CH3OH and indicate a less flexible structure in CH3CN. Pulse gradient spin echo (PGSE) NMR measurements correlate these findings to molecular dimensions. A reduced size for the dendrons in CH3CN compared to CH3OH leads to the assumption of a more compact structure in this solvent. Additional polarimetric data reveal, that observed changes in optical activity with increasing generation can in CH3OH be explained by constitutional effects of the dendron structure but not in CH3CN. CD measurements are in agreement with these findings and show a linear increase of the Cotton effects with increasing generation for CH3OH but not for CH3CN. It can be concluded that the conformation within the dendrons is very sensitive to environmental conditions and that a chiral secondary structure might be stabilized in CH3CN. Initial studies revealed that chirality transfer to the focal functionality occurs.
- Buschhaus, Boris,Bauer, Walter,Hirsch, Andreas
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p. 3899 - 3915
(2007/10/03)
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- An improved synthesis of aziridine-2,3-dicarboxylates via azido alcohols - Epimerization studies
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The reasons for epimerization of 3-azido-2-hydroxysuccinates observed during the ring opening of epoxides or cyclic sulfites with sodium azide is now clarified. It is caused by the high acidity of the proton at the 3-position. This is proven by a proton deuterium exchange in assays with either D 2O or DCl containing solvents. The anti-3-azido-2-hydroxysuccinates serve as intermediates for enantiomerically pure trans-aziridine-2,3- dicarboxylates for which an optimized synthetic pathway is presented. The first example of an enantiomerically pure mixed diester of the aziridine-2,3- dicarboxylic acid the synthesis of the allyl ethyl ester is reported herein.
- Breuning, Alexander,Vicik, Radim,Schirmeister, Tanja
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p. 3301 - 3312
(2007/10/03)
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- Molecular control over semiconductor surface electronic properties: Dicarboxylic acids on CdTe, CdSe, GaAs, and InP
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We present "design rules" for the selection of molecules to achieve electronic control over semiconductor surfaces, using a simple molecular orbital model. The performance of most electronic devices depends critically on their surface electronic properties, i.e., surface band-bending and surface recombination velocity. For semiconductors, these properties depend on the density and energy distribution of surface states. The model is based on a surface state-molecule, HOMO-LUMO-like interaction between molecule and semiconductor. We test it by using a combination of contact potential difference, surface photovoltage spectroscopy, and time- and intensity-resolved photoluminescence measurements. With these, we characterize the interaction of two types of bifunctional dicarboxylic acids, the frontier orbital energy levels of which can be changed systematically, with air-exposed CdTe, CdSe, InP, and GaAs surfaces. The molecules are chemisorbed as monolayers onto the semiconductors. This model explains the widely varying electronic consequences of such interaction and shows them to be determined by the surface state energy position and the strength of the molecule-surface state coupling. The present findings can thus be used as guidelines for molecule-aided surface engineering of semiconductors.
- Cohen,Kronik,Shanzer,Cahen, David,Liu,Rosenwaks,Lorenz,Ellis
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p. 10545 - 10553
(2007/10/03)
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- Enantioselective synthesis of cyclothiazide analogues: Novel probes of the stereospecific actions of benzothiadiazines at AMPA-type glutamate receptors
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The stereospecific interactions of the eight stereoisomers of dihydromethylcyclothiazide, an analogue of cyclothiazide, with AMPA-type glutamate receptors was investigated using electrophysiological methods that measured the ability of each stereoisomer to inhibit AMPA receptor desensitization. The eight stereoisomers were obtained by HPLC separation of four pairs of enantiomerically pure (>95% ee) diastereomers prepared from (1R-exo)-, (1R-endo)-, (1S-exo)-, and (1S-endo)-2-methylbicyclo[2.2.1]heptane-2-carboxaldehyde intermediates. The desensitization process was blocked most potently by [1S-[1α,2α(R*),4α]]-dihydromethylcyclothiazide, one of the stereoisomers prepared from the (1S-endo)-carboxaldehyde. The smallest effects on the desensitization process were found for the four stereoisomers prepared from the (1R-exo)- and (1R-endo)-carboxaldehydes. Significant differences in the ability to inhibit desensitization were observed between all diastereomer pairs except those prepared from the (1S-exo)-carboxaldehyde.
- Hu, Yuefei,Yamada, Kelvin A.,Chalmers, David K.,Annavajjula, Durga P.,Covey, Douglas F.
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p. 4550 - 4559
(2007/10/03)
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- Enantioselective distribution of amino-alcohols in a liquid-liquid two-phase system containing dialkyl L-tartrate and boric acid
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Racemic amino-alcohols such as pindolol, propranolol, alprenolol and bucumolol enantiomers exhibited different distribution behaviors in a two-phase system consisting of a chloroform solution of didodecyl L-tartrate and an aqueous solution of boric acid. It seemed that a borate complex of the 1,2-diol group of the tartrate and the amino-alcohol was formed in the system. In the case of pindolol, one enantiomer was preferentially extracted into the organic phase (x 2.20) at equilibrium.
- Abe,Shoji,Kobayashi,Qing,Asai,Nishizawa
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p. 262 - 265
(2007/10/02)
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- Use of 1,3-dioxin-4-ones and related compounds in synthesis. XLIV. Asymmetric aldol reaction of 4-trimethylsiloxy-6-methylene-1,3-dioxines: Use of tartaric acid-derived (acyloxy)borane complex as the catalyst
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A novel enantioselective synthesis of 1,3-dioxin-4-ones having a 2-hydroxylated alkyl group at the 6-position has been accomplished by chiral tartaric acid-derived acylborane-mediated aldol condensation of the silyl enol ether derived from 6-methyl-derivatives of 1,3-dioxin-4-one with achiral aldehydes.
- Sato,Sunami,Sugita,Kaneko
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p. 839 - 845
(2007/10/02)
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- A CONVENIENT METHOD FOR ENZYMATIC BENZYL-ALKYL TRANSESTERIFICATION UNDER MILD NEUTRAL CONDITIONS
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Lipases from Candida cylindracea and from Pseudomonas fluorescens efficiently catalyse the benzyl to alkyl transesterification in organic solvents under mild conditions in nearly quantitative yields.
- Gutman, Arie L.,Shkolnik, Eleonora,Shapira, Michal
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p. 8775 - 8780
(2007/10/02)
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- The Reaction of Thioimides with Phosphorus Ylides
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The reaction of a series of thioimides with phosphorus ylides, in a manner analogous to the Wittig reaction, has been examined.The resulting reaction products represent potentially valuable intermediates in tetrapyrrole pigment synthesis.In addition to the desired thio-Wittig-type coupling reaction, the presence of two competing reaction pathways, S-alkylation and oxidation/reduction, has been observed with certain substrates.These empirical observations have been correlated to theoretical data, derived from MNDO and ab initio calculations, which delineate the structu re-reactivity relationships governing product distribution from the various reaction pathways.A detailed analysis is presented of the mechanism of the thio-Wittig coupling reaction and the competitive S-alkylation reaction.
- Bishop, John E.,O'Connell, John F.,Rapoport, Henry
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p. 5079 - 5091
(2007/10/02)
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- Reductive Cross Coupling Reaction of a Glyoxylate with Carbonyl Compounds. A Facile Synthesis of α,β-Dihydroxycarboxylate Based on a Low Valent Titanium Compound
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On treatment with a low valent titanium compound, a glyoxylate is reductively converted to the titanium enediolate, which reacts with carbonyl compounds to give the corresponding adducts, α,β-dihydroxycarboxylates, in good yields.
- Mukaiyama, Teruaki,Sugimura, Hideo,Ohno, Takashi,Kobayashi, Shu
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p. 1401 - 1404
(2007/10/02)
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