- An efficient synthetic approach towards fully functionalized tetronic acids: The use of 1,3-dioxolane-2,4-diones as novel protected-activated synthons of α-hydroxy acids
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A new strategy for the synthesis of tetronic acids with control over the regioselective introduction of substituents at the C-5 position has been developed. The construction of the densely functionalized quaternary carbon center within these molecules is of great importance. The key element for the proposed protocol was the utilization of O-carboxyanhydrides (OCA's) of optically active α-hydroxy acids, as promising bidentate protective/activating precursors. The structure of the new compounds was investigated by using NMR spectral data and X-ray structural analyses.
- Prousis, Kyriakos C.,Markopoulos, John,Mckee, Vickie,Igglessi-Markopoulou, Olga
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p. 8637 - 8648
(2015/10/19)
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- Method for the Production of 1,3-Dioxolane-2-Ones and Carboxylic Acid Esters by Means of Transacylation in Basic Reaction Conditions
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The invention relates to a method for producing 1,3-dioxolane-2-ones of general formula (3) in basic reaction conditions by reesterifying the respective ester of general formula (1) in which R1 to R5 have the meanings indicated in the claims and the descr
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Page/Page column 10-11
(2010/12/29)
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- Organocatalytic diastereo- And enantioselective Michael addition reactions of 5-aryl-1,3-dioxolan-4-ones
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5-Aryl-1,3-dioxolan-4-one heterocycles derived from mandelic acid derivatives and hexafluoroacetone have been identified as new and effective pro-nucleophiles in highly diastereo- and enantioselective Michael addition reactions to nitro olefins catalyzed
- Hynes, Peter S.,Stranges, Daniela,Stupple, Paul A.,Guarna, Antonio,Dixon, Darren J.
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p. 2107 - 2110
(2008/02/02)
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- Nucleophilic benzoylation using a mandelic acid dioxolanone as a synthetic equivalent of the benzoyl carbanion. Oxidative decarboxylation of α-hydroxyacids
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The synthesis of alkyl aryl ketones using a mandelic acid dioxolanone as a synthetic equivalent (Umpolung) of the benzoyl carbanion is reported. The methodology involves alkylation of the mandelic acid dioxolanone, hydrolysis of the dioxolanone moiety in the alkylated products and oxidative decarboxylation of the resulting α-hydroxyacids. The last step is carried out in a catalytic aerobic way using a Co (III) complex in the presence of pivalaldehyde under very mild conditions.
- Blay, Gonzalo,Fernandez, Isabel,Monje, Belen,Pedro, Jose R.
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p. 365 - 372
(2007/10/03)
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- Controlled racemization and asymmetric transformation of α-substituted carboxylic acids in the melt
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The racemization and asymmetric transformation of a series of α- substituted carboxylic acids, viz. mandelic acid, hydratropic acid, ibuprofen and naproxen, were studied. Several racemization methods for mandelic acid were studied and it was found that base-catalyzed racemization in aprotic polar solvents was the most efficient method. Moreover, a fast and mild base- catalyzed racemization reaction in the melt was developed. DBN turned out to be a very efficient racemizing base for the substrates studied. Combination of the base-catalyzed racemization in the melt with known resolution processes resulted in crystallization-induced asymmetric transformations. Treating racemic ibuprofen or hydratropic acid with 1.5-2.5 equivalents of enantiopure α-methylbenzylamine and a catalytic amount of DBN resulted in the isolation of enantiomerically enriched ibuprofen or hydratropic acid with ees of up to 75% and almost quantitative yields.
- Ebbers, Eelco J.,Ariaans, Gerry J. A.,Bruggink, Alle,Zwanenburg, Binne
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p. 3701 - 3718
(2007/10/03)
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- Behaviour of dioxolanones as chiral acyl anion equivalents
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The 1,3-dioxolan-4-ones readily derived from α-hydroxy acids act as convenient acyl anion equivalents by deprotonation - alkylation followed by flash vacuum pyrolysis. Conjugate addition of their anions to ethyl crotonate similarly gives β-methyl-γ-oxo esters and by using chiral dioxolanones these can be obtained in up to 86% e.e.
- Aitken, R. Alan,Thomas, Andrew W.
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p. 102 - 104
(2007/10/03)
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- Stereoselective synthesis and biodistribution of potent [11C]-labeled antagonists for positron emission tomography imaging of muscarinic receptors in the airways
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Quantitation of muscarinic receptors in the lungs in vivo with positron emission tomography (PET) is of clinical interest. For that purpose we decided to develop [11C]-labeled ligands with a high affinity (K(D) 11C]CH3I with their tertiary amine precursors. The enantiomerically pure tertiary amine precursors were prepared by stereoselective synthesis starting from (R)-(-)-mandelic acid. In vitro binding assay of 1b and 2 demonstrated that both ligands bind with very high affinity to the muscarinic receptor subtypes M1, M2, and M3. They are more potent than the muscarinic antagonist (R)-N-methylquinuclidinyl benzilate ((R)-MQNB). Distribution studies with 1a, 1b, and 2 in control and atropine- treated male Wistar rats demonstrated significant specific binding (90-99% of total issue uptake) in tissues containing cholinoceptors (heart, intestine, lung, pancreas, spleen, stomach, submandibular gland). Because the tissue/plasma concentration ratios of lb are most favorable, this ligand was used for further evaluation. Analysis of plasma samples showed a very rapid clearance (t(1/2) = 0.3 min) of the radioligand 1b and a relatively slow appearance of a hydrophilic metabolite. At 15 min postinjection of 1b, analysis of heart, lungs, and liver showed that respectively 99%, 88%, and 8% of the tissue radioactivity corresponded with the parent compound. Ligand 1b appears to be an excellent candidate for PET studies of mAChR receptors in heart and lungs.
- Visser, Ton J.,Van Waarde, Aren,Jansen, Twan J. H.,Visser, Gerben M.,Van Der Mark, Thom W.,Kraan, Jan,Ensing, Kees,Vaalburg, Willem
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p. 117 - 124
(2007/10/03)
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- Stereoselective Protonation of Carbanions, 4. Enantioselective Protonation of Lactone Enolates
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The prochiral lithium enolates derived from the five-membered lactones rac-1 and rac-2 were protonated by 37 OH- and 21 NH-chiral proton sources in THF at -78 deg C.The enantioselectivities, determined directly from the reaction mixture by chiral HPLC, ar
- Gerlach, Uwe,Haubenreich, Thomas,Huenig, Siegfried
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p. 1969 - 1980
(2007/10/02)
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- Deracemization of silyl enol ethers
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The deracemization by enantioselective protonation of silyl enol ethers was tested using 2,2-dimethyl 5-phenyl 1,3-dioxolan-4-one 1. The results obtained, especially with pantolactone as a chiral proton donor, are better than when the deracemization is ca
- Cavelier,Gomez,Jacquier,Verducci
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p. 2501 - 2505
(2007/10/02)
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- Palladium-catalyzed allylation of α-hydroxy acids
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Mandelic and lactic acids are converted to the 1,3-dioxolan-4-ones by treatment with acetone dimethyl acetal.Deprotonation followed by treatment with an allyl acetate and a catalytic amount (1 mol percent) of palladium catalyst afforded the allylated dioxolanones, which could be hydrolyzed to the corresponding α-allyl α-hydroxy acids.The lithium enolate of the dioxolanone of mandelic acid was also coupled with methallyl, cinnamyl, geranyl and (E)-1-methyl-2-butenyl acetates.The zinc enolate of the dioxolanone of lactic acid reacted smoothly with allyl acetate in a catalyzed reaction whereas no detectable reaction was observed when the lithium enolate was used.This appears to be the result of complications arising from the enhanced basicity of the lithium compared to zinc enolate.Various attempts were made to achieve enantioselectivity using chiral ligands on the palladium catalyst.The zinc enolates were found to provide better results although the enantioselectivity was only modest, about 30percent enantiomeric excess being the best result obtained.Chiraphos proved to be the best optically active ligand of a variety tested.
- Moorlag, Henk,Vries, Johannes G. de,Kaptein, Bernard,Schoemaker, Hans E.,Kamphuis, Johan,Kellogg, Richard M.
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p. 129 - 137
(2007/10/02)
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- Pig Liver Esterase Catalyzed Hydrolyses of Racemic α-Substituted α-Hydroxy Esters
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Pig liver esterase catalyzed hydrolyses of some α-substituted α-hydroxy esters give product acids and recovered esters in 9-94percent enantiomeric excess.The observed enantiomeric selectivity could be rationalized using a recently proposed active site mod
- Moorlag, Henk,Kellogg, Richard M.,Kloosterman, Marcel,Kaptein, Bernard,Kamphuis, Johan,Schoemaker, Hans E.
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p. 5878 - 5881
(2007/10/02)
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- ASYMMETRIC SYNTHESIS OF α-HYDROXY CARBOXYLIC ACIDS: DIRECT OXIDATION OF CHIRAL AMIDE ENOLATES USING 2-SULFONYLOXAZIRIDINES
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The direct oxidation of chiral amide enolates to optically active mandelic acid using 2-sulfonyloxaziridine 1 is described.The diastereoselectivity is counterion dependent.
- Davis, Franklin A.,Vishwakarma, Lal C.
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p. 3539 - 3542
(2007/10/02)
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