- Synthesis and electrochemical properties of a chiral silyl-substituted tetrathiafulvalene derivative
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A new chiral tetrathiafulvalene (TTF) derivative and related silyl-substituted 1,3-dithiole-2-(thi)one compounds were synthesized and characterized by 1H NMR, 13C NMR, MS and IR spectra. Single crystal structure of the silyl-substituted 1,3-dithiole-2-one revealed the high degree of conjugation of the five-membered ring moiety in the compound. The electrochemical properties of the new TTF derivative were studied by cyclic voltammetry and the results indicated that the electron-donating ability of the chiral TTF derivative was similar to that of BEDT-TTF. The ΔE value for the new TTF derivative was smaller than those for TTF and BEDT-TTF, indicative of decreased Coulombic repulsion in the dicationic redox state. Formation of charge-transfer (CT) complex between the new donor and electron acceptor 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ) was demonstrated.
- Liang, Guo-Qi,Zhang, Zhong-Bao,Li, Hong-Qi,Wang, Ya-Ping,Xian, Chun-Ying
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- Synthesis of [7]Helicene Enantiomers and Exploratory Study of Their Conversion into Helically Chiral Iodoarenes and Iodanes
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The facile and convenient preparation of both enantiomers of a [7]helicene scaffold from inexpensive (l)-(+)-tartaric acid and 4-methylstyrene is described. These helical structures were transformed into bis-iodinated ether derivatives in order to explore their potential as precursors of novel chiral organoiodane reagents or as iodoarene pre-catalysts. Promising results were obtained in hydroxylative phenol dearomatization/[4+2] cycloaddition cascade and dearomative spirolactonization reactions with encouraging enantiomeric excesses.
- Antien, Kevin,Pouységu, Laurent,Deffieux, Denis,Massip, Stéphane,Peixoto, Philippe A.,Quideau, Stéphane
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p. 2852 - 2858
(2019/02/05)
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- Palladium- and Rhodium-Catalyzed Dynamic Kinetic Resolution of Racemic Internal Allenes Towards Chiral Pyrazoles
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A complementing Pd- and Rh-catalyzed dynamic kinetic resolution (DKR) of racemic allenes leading to N-allylated pyrazoles is described. Such compounds are of enormous interest in medicinal chemistry as certified drugs and potential drug candidates. The new methods feature high chemo-, regio- and enantioselectivities aside from displaying a broad substrate scope and functional group compatibility. A mechanistic rational accounting for allene racemization and trans-alkene selectivity is discussed.
- Hilpert, Lukas J.,Sieger, Simon V.,Haydl, Alexander M.,Breit, Bernhard
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p. 3378 - 3381
(2019/02/06)
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- Synthesis of hybrid 1,2,3-triazolo-δ-lactams/lactones using Huisgen [3+2] cycloaddition 'click-chemistry' in water
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The synthesis of a new class of hybrid 1,2,3-triazozlo-δ-lactams/lactones has been achieved using the Huisgen [3+2] dipolar cycloaddition 'click-chemistry' reaction of various organic azides with an activated alkyne in water, followed by cyclization.
- Kumar, Indresh,Rana, Sravendra,Cho, Jae Whan,Rode, Chandrashekhar V.
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scheme or table
p. 352 - 355
(2010/06/16)
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- NEUROLOGICALLY-ACTIVE COMPOUNDS
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The invention provides a compound of the formula (I): wherein R is methyl, ethyl, propyl, isopropyl, butyl, pentyl, neo-pentyl or cyclohexyl, or a salt or solvate thereof. These compounds are selective GABAC receptor antagonists. The invention also provides pharmaceutical compositions comprising a compound of formula (I) or a pharmaceutically acceptable salt or solvate thereof. The invention also provides methods of enhancing the cognitive activity of an animal and methods of stimulating memory capacity in an animal, comprising the step of administering to the animal an effective amount of a compound of formula (I) or a pharmaceutically acceptable salt or solvate thereof.
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Page/Page column 11; 16
(2008/06/13)
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- Synthesis of chiral hydroxythiolanes as potential catalysts for asymmetric organozinc additions to carbonyl compounds
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Optically active 3-hydroxythiolane was stereospecifically synthesized from L-aspartic acid and oxidized to give both diastereomeric S-oxides, which were chromatographicatly separated and their configuration was determined. Starting from natural (+)-(R,R)-tartaric acid, C2-symmetric trans-(R,R)-3,4-dihydroxythiolane was stereospecifically synthesized for the first time. Some of its monofunctionalized derivatives as well as its S-oxide were also obtained and characterized. meso-cis-3,4-Dihydroxythiolane was obtained in a similar way from meso-tartaric acid and subjected to desymmetrization either by a lipase-promoted acetylation or hydrolysis of the corresponding O, O'-diacetyl derivative, to give a chiral monoacetate with ee up to 36%. After its oxidation two diastereomeric sulfoxides were obtained which were separated by chromatography. The crystalline one was subjected to X-ray analysis and its absolute configuration was determined as 1S, 3S, 4R. All the optically active products were checked as potential catalysts for asymmetric addition of diethylzinc to benzaldehyde. However, they proved to have a very low catalytic activity: yields of the products were in the range 10-90% but ee only up to 10%. A conclusion was drawn that in this type of reaction neither is the hydroxy sulfide (sulfoxide) moiety capable of properly binding diethylzinc, nor does the sulfinyl group exert its normal stereoinduction.
- Kielbasinski, Piotr,Albrycht, Malgorzata,Mikolajczyk, Marian,Wieczorek, Michal W.,Majzner, Wieslaw R.,Filipczak, Agnieszka,Ciolkiewicz, Piotr
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- Silver(I) oxide mediated highly selective monotosylation of symmetrical diols. Application to the synthesis of polysubstituted cyclic ethers
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(Matrix Presented) The reaction of symmetrical diols and oligo(ethylene glycol)s with a stoichiometric amount of p-toluenesulfonyl chloride in the presence of silver(I) oxide and a catalytic amount of potassium iodide led selectively to the monotosylate derivatives in high yields. Polysubstituted cyclic ethers were obtained readily upon treatment of the corresponding diols with an excess of silver oxide. The high selectivity was explained on the basis of the difference in acidity between the two hydroxy groups, which undergo an intramolecular hydrogen bonding.
- Bouzide, Abderrahim,Sauve, Gilles
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p. 2329 - 2332
(2007/10/03)
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- Total synthesis of koninginin D, B and E
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Total synthesis of koninginin D, E and B was described. The structures of koninginin B and F, which were deduced as C4 epimer of koninginin E and D, respectively, have been corrected.
- Liu,Wang
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p. 119 - 127
(2007/10/03)
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- First total synthesis of (+)-koninginin D
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A total synthesis of (+)-koninginin D (1) is described; the absolute configuration of the immediate antecedent of 1 is shown to have the configuration 7R,9S,10S by X-ray diffraction analysis.
- Liu, Gang,Wang, Zhiqin
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p. 1129 - 1130
(2007/10/03)
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- Enolic ortho esters. VIII. Synthesis of (2S,3S)-2,3-bis(methoxymethyl)-1,4,6-trioxaspiro[4.5]dec-7-ene
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Enolic ortho ester (2S,3S)-2,3-bis(methoxymethyl)-1,4,6-trioxaspiro[4.5]dec-7-ene (10b) was synthesized in 65% yield by cycloadditon of acrolein with the ketene acetal (4S,5S)-4,5-bis(methoxymethyl)-2methylidene-1,3-dioxolan (7), derived by potassium t-butoxide treatment of (4S,5S)-4,5-bis(methoxymethyl)-1,3-dioxolan (4). Lewis acid catalysed reaction (TiCl4, CH2Cl2, -78°) of the enolic ortho ester (10b) with the ketene silyl acetal 3-phenylmethyl-2-trimethylsilyloxy-4,5-dihydrofuran (15) afforded the formyl keto ester 3-[4′,5′-bis(methoxymethyl)-2′-(4″-oxobutyl)-1′, 3′-dioxolan-2′-yl]-3-phenylmethyl-4,5-dihydrofuran-2(3H)-one (16) (39%) with only poor diastereoselectivity. Attempts to make the bis(phenylmethyl) analogue (10a) of enolic ortho ester (10b) were thwarted by the finding that the required ketene acetal (9), analogous to (7), could not be generated by elimination from (4S,5S)-2-bromomethyl-4,5-bis(phenylmethyl)-1,3-dioxolan (6), or from the derived phenyl selenoxide (8), under a variety of conditions.
- Collins, David J.,Crosby, Ian T.
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p. 1025 - 1030
(2007/10/03)
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- An Efficient Synthesis of 4(S)-Hydroxycyclopent-2-enone
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An efficient synthesis of 4(S)-hydroxycyclopent-2-enone of high optical purity, a key synthon used in natural product synthesis, is described.The method is suitable for large-scale synthesis.
- Khanapure, Subhash P.,Najafi, Nahid,Manna, Sukumar,Yang, Jing-Jing,Rokach, Joshua
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p. 7548 - 7551
(2007/10/03)
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- Synthesis and the Absolute Configuration of Panaxacol
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Panaxacol, a polyacetylene isolated from the callus of Panax ginseng, was synthesized from D-(-)-diethyl tartrate.The absolute configuration of panaxacol was determined to be 9R,10R.
- Fujimoto, Yasuo,Satoh, Mitsuru,Takeuchi, Naoki,Kirisawa, Makoto
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p. 1619 - 1622
(2007/10/02)
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- Macroheterocycles. 34. Synthesis and Enantiomeric Selectivity of Chiral Azacrown
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Chiral azacrown ethers were obtained by the condensation of (4S,5S)-4,5-ditosyloxymethyl-2,2-dimethyl-1,3-dioxolane with 6-benzyl-3,9-dioxa-6-azaundecane-1,11-diol.Their debenzylation and deacetalization were realized.The enantiomeric selectivity in the complex formation between the obtained crown ethers and the hydrochlorides of L- and D-valine methyl esters was determined by a potentiometric method.The chiral azacrown ethers exhibit higher enantioselectivity than their oxygen analogs.
- Luk'yanenko, N. G.,Lobach, A. V.,Nazarova, N. Yu.,Karpenko, L. P.,Lyamtseva, L. N.
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p. 562 - 566
(2007/10/02)
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- Preparation of (4R,5S)-(5-methyl-2,2-dimethyl-1,3-dioxolane-4-ylmethyl)-phosphonium iodide. A synthetic approach to olguine: further model studies
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The enantiomerically pure title compound ((4R,5S)-(5-methyl-2,2-dimethyl-1,3-dioxolane-4-ylmethyl)-phosphonium iodide) has been synthesized starting from (R,R)-(+)-tartaric acid.The synthesis of an oliguine analog has been carried out.Attempts have been made to improve the stereoselectivity and yield of key steps.
- Valverde, Serafin,Herradon, Bernardo,Rabanal, Rosa M.,Martin-Lomas, Manuel
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p. 332 - 338
(2007/10/02)
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- STEREOSPECIFIC SYNTHESIS OF ISOMERIC 4-SUBSTITUTED 9-(2,3-DIHYDROXYBUTYL)ADENINES
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Reduction of ethyl 2,3-O-isopropylidene-D-tartrate with sodium borohydride afforded (4S,5S)-2,2-dimethyl-1,3-dioxolane-4,5-dimethanol (Va) which was benzoylated to give monobenzoyl derivative Vd and further transformed into p-toluenesulfonyl derivative Ve.Reaction of the compound Ve with sodium salt of adenine followed by methanolysis gave 2,3-O-isopropylidene derivative Vf which on acid hydrolysis afforded 9-(2S,3S)-(2,3,4-trihydroxybutyl)adenine (Ia).The enantiomer IIa was obtained from 3,4-O-isopropylidene-D-mannitol via (4R,5R)-2,2-dimethyl-1,3-dioxolane-4,5-dimethanol (VIa) using the same procedure.Reaction of compounds Vf and VIf with p-toluenesulfonyl chloride afforded 4-O-p-toluenesulfonyl derivatives Vg and VIg.These compounds were also obtained from Va and VIa via di-p-toluenesulfonyl derivatives Vc and VIc by reaction with sodium salt of adenine.Treatment of compounds Vg and VIg with sodium iodide gave 4-iodo derivatives Vh and VIh which on reaction with tri-n-butyltin hydride, followed by acid hydrolysis, afforded enantiomeric threo-2,3-dihydroxybutyl derivatives Ib and IIb.Compounds Vg and VIg on treatment with sodium azide, subsequent catalytic hydrogenation of the intermediates Vj and VIj and acid hydrolysis afforded enantiomeric threo-9-(4-amino-2,3-dihydroxybutyl)adenines (Ic, IIc).Reaction of methyl threo-3-phenylglycerate (VIIb) with acetone, followed by reduction with lithium aluminum hydride, gave 2,2-dimethyl-4-phenyl-1,3-dioxolane-5-methanol (VIIIb) which was converted by reaction with p-toluenesulfonyl chloride, condensation with sodium salt of adenine and acid hydrolysis into 9-(RS)-threo-(3-phenyl-2,3-dihydroxypropyl)adenine (I, IId).Methyl ester of D-eritadenine (IXb) was transformed into 2,3-O-isopropylidene derivative XIa which on reduction with sodium borohydride afforded the alcohol XIb.Its acid hydrolysis gave 9-(2R,3S)-erythro-(2,3,4-trihydroxybutyl)adenine (IIIa); tosylation of compound XIb, successive treatment with sodium iodide and tri-n-butyltin hydride and acid hydrolysis afforded 9-(2R,3S)-erythro-(2,3-dihydroxybutyl)adenine (IIIb).The enantiomers IVa and IVb were obtained analogously from L-eritadenine.The racemic derivative Ib + IIb was prepared from (RS)-threo-2,3-dihydroxybutyric acid via p-toluenesulfonyl derivative of racemic 2,2,4-trimethyl-1,3-dioxolane-5-methanol (IIIc) by reaction of sodium salt of adenine followed by acid hydrolysis.
- HOLY, Antonin
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p. 173 - 189
(2007/10/02)
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- PREPARATION AND CHIRAL RECOGNITION OF NEW CHIRAL 18-CROWN-6 ETHERS
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Four new chiral macrocyclic polyethers of 18-crown-6 type which have phenyl, 1-naphtyl or tetramethylphenyl substituents were prepared , and their chiral recognition for 1-phenylethylamine was discussed.
- Yamashita, Junzo,Minagawa, Masaaki,Sonobe, Akihiro,Ohashi, Shoichi,Kawamura, Misao,et al
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p. 1409 - 1412
(2007/10/02)
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- Asymmetric hydroformylation process
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This invention relates to a process for the preparation of optically active aldehydes by the asymmetric catalytic hydroformylation of olefins. The process comprises the hydroformylation of olefinically unsaturated prochiral compounds in the presence of an optically active coordination compound containing a metal which is selected from the group consisting of rhodium, iridium, and cobalt. This invention describes a generalized process for the asymmetric hydroformylation of a wide variety of olefins in which a preponderance of one optical isomer is produced. It is especially useful for the preparation of natural products which may require the presence of only one optical isomer for their utilization, for example, as flavors, fragrances, and medications. The catalyst systems for the process of this invention are formed in the presence of carbon monoxide and hydrogen, from coordination compounds consisting of a central metal atom, rhodium, iridium, or cobalt, and at least one optically active ligand, e.g., phosphine, arsine, stibine, or amine. The coordination compound may contain one or more additional ligands, which may be neutral or which may possess negative charges such as carbon monoxide, hydrogen, olefins and diolefins, and halides.
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- Cyclodiop, an example of a new class of chiral diphosphines
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Cyclodiop, a chiral diphosphine with an intact PP bond was prepared and used as a ligand in rhodium complexes. Asynunetric reduction of some prochiral olefins was observed. The nature of the rhodium complexes is discussed in the light of their P nmr spectra.
- Zhang,Yemul,Kagan,Stern,Commereuc,Chauvin
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p. 3955 - 3958
(2007/10/02)
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- Novel Copper Complexes of Chiral Diphosphines: Preparation, Structure, and Use To Form Rhodium Complex Catalysts for Chiral Hydrogenations
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Treatment of chiral diphosphines 5a-c and 13 ("DIOP", aryl derivatives and related substances) with CuCl in boiling ethanol gave complexes having the composition n, 6a-c and 11.Crystallizations of 6a-c from crude 70-80percent pure 5a-c and decomposition of the complexes by ammonia gave the pure diphosphines.Ligand exchange between 6a-c and 2 in methanol at 23 deg C was rapid and complete.Treatment of the resulting solutions with H2 gave active catalysts for asymmetric hydrogenations.
- Townsend, John M.,Blount, John F.,Sun, Ruen Chu,Zawoiski, Sonja,Valentine, Donald
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p. 2995 - 2999
(2007/10/02)
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