- A traceless photocleavable linker for the automated glycan assembly of carbohydrates with free reducing ends
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We report a traceless photocleavable linker for the automated glycan assembly of carbohydrates with free reducing ends. The reductive-labile functionality in the linker tolerates all commonly used reagents and protocols for automated glycan assembly, as demonstrated with the successful preparation of nine plant cell wall-related oligosaccharides, and is cleaved by hydrogenolysis.
- Wilsdorf,Schmidt,Bartetzko,Dallabernardina,Schuhmacher,Seeberger,Pfrengle
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p. 10187 - 10189
(2016/08/18)
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- Rhodium-catalyzed asymmetric hydrogenation of olefins with PhthalaPhos, a new class of chiral supramolecular ligands
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A library of 19 binol-derived chiral monophosphites that contain a phthalic acid diamide group (Phthala- Phos) has been designed and synthesized in four steps. These new ligands were screened in the rhodium-catalyzed enantioselective hydrogenation of prochiral dehydroamino esters and enamides. Several members of the library showed excellent enantioselectivity with methyl 2-acetamido acrylate (6 ligands gave >97% ee), methyl (Z)-2- acetamido cinnamate (6 ligands gave >94% ee), and N-(1-phenylvinyl)acetamide (9 ligands gave >95% ee), whilst only a few representatives afforded high enantioselectivities for challenging and industrially relevant substrates N-(3,4-dihydronaphthalen-1- yl)-acetamide (96% ee in one case) and methyl (E)-2-(acetamidomethyl)-3- phenylacrylate (99% ee in one case). In most cases, the new ligands were more active and more stereoselective than their structurally related monodentate phosphites (which are devoid of functional groups that are capable of hydrogen-bonding interactions). Control experiments and kinetic studies were carried out that allowed us to demonstrate that hydrogen-bonding interactions involving the diamide group of the PhthalaPhos ligands strongly contribute to their outstanding catalytic properties. Computational studies carried out on a rhodium precatalyst and on a conceivable intermediate in the hydrogenation catalytic cycle shed some light on the role played by hydrogen bonding, which is likely to act in a substrate-orientation effect.
- Pignataro, Luca,Boghi, Michele,Civera, Monica,Carboni, Stefano,Piarulli, Umberto,Gennari, Cesare
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p. 1383 - 1400
(2012/03/27)
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- Phthalaphos: Chiral supramolecular ligands for enantioselective rhodium-catalyzed hydrogenation reactions
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Interligand hydrogen bonding of chiral monodentate phosphite ligands bearing H-bond donor and acceptor groups leads to formation of supramolecular bidentate ligands, rhodium complexes of which (see picture) afford excellent enantiomeric excesses in catalyzed hydrogenation of classical benchmark and industrially relevant substrates. cod=1,5-cyclooctadiene.
- Pignataro, Luca,Carboni, Stefano,Civera, Monica,Colombo, Raffaele,Piarulli, Umberto,Gennari, Cesare
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supporting information; experimental part
p. 6633 - 6637
(2010/10/21)
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- 1,2,3,4-Tetrahydropyrazin-2-yl acetamides and methods of use
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Selected compounds are effective for treatment of pain and diseases, such as inflammation mediated diseases. The invention encompasses novel compounds, analogs, prodrugs and pharmaceutically acceptable derivatives thereof, pharmaceutical compositions and
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Page/Page column 54
(2010/02/15)
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- Amidine derivatives and cardiotonic compositions
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Amidine derivatives of the formula STR1 wherein R1 and R2, which may be the same or different, represent each a hydrogen atom or a lower alkyl group, or R1 and R2 together with an intermediary carbon atom and/or hetero atom may form a ring; X represents STR2 (wherein R8 represents a hydrogen atom, a lower alkyl group, or --CH2 COOR9, where R9 represents a hydrogen atom or a lower alkyl group; Z represents a single bond, --CH2 --, --CH2 CH2 --, or --CH=CH--); R3 represents a hydrogen or chlorine atom, methoxy group, nitro group, or amino group; Y represents --CH2 CH2 --, --CH=CH--, --CH2 O--, or --OCH2 --; R4 represents a hydrogen atom, methoxy group, benzoyl group, nitro group, or amino group; and R5, R6 and R7, which may be the same or different, represent each a hydrogen atom, lower alkyl group, cycloalkyl group, aralkyl group, substituted alkyl group, substituted aralkyl group, or amino group, or R5 and R7 may form a ring, or salts thereof have an excellent cardiotonic activity and can be used as cardiotonics.
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- A Model for Nicotinamide-Tryptophane Charge-Transfer Interactions: the Complexation of Nicotinamide-Ammonium Salts by a Macrocyclic Receptor Molecule Bearing Tryptophane Side Chains
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The complexation of primary ammonium salt substrates by macrocyclic polyether receptor molecules provides a general method for studying the nature and stereochemistry of intermolecular interactions.The substrates and receptors are fitted with one of the interacting units and the resulting effects in the complex are analyzed.The method is used to study the biologically important indole-pyridinium donor-acceptor interaction.The complexes between macrocycles, bearing an indole group in side chains, and pyridinium-ammonium salts display a characteristic charge-transfer band.The absorption coefficients and stability constants have been determined.Competition experiments also provide a new method for measuring the stability constants of macrocycle-ammonium complexes in organic solvents.
- Behr, Jean-Paul,Lehn, Jean-Marie
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p. 2112 - 2118
(2007/10/02)
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