- Synthesis of chiral β-chalcogen amine derivatives and Gram-positive bacteria activity
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Efficient ring opening reaction between aziridines and diphenyl dichalogenides using HCl, Zn° in ionic liquid is disclosed, affording chiral β-chalcogen amines derivatives in good yields under mild reaction condition. The ionic liquid was further reused f
- Vargas, Josimar,Gul, Kashif,Ravanello, Bruno B.,Dornelles, Luciano,Soares, Letiere C.,Rodrigues, Oscar E. D.,Narayanaperumal, Senthil,Alves, Camilla F. S.,Schneider, Taiane,Vaucher, Rodrigo De A.,Santos, Roberto C. V.
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supporting information
p. 10444 - 10448,5
(2012/12/12)
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- Synthesis of new fluorous modular chiral ligand derivatives from amino alcohols and application in enantioselective carbon-carbon bond-forming alkylation reactions
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N-Trifluoracyl β-chalcogeno amides and N-perfluoracyl β-thio amide ligands were prepared by a simple and efficient reaction sequence. These new ligands were evaluated in palladium-catalyzed alkylation of rac-(E)-1,3-diphenyl-2-propenyl acetate in the pres
- Sehnem, Jasquer A.,Milani, Priscila,Nascimento, Vanessa,Andrade, Leandro H.,Dorneles, Luciano,Braga, Antonio L.
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scheme or table
p. 997 - 1003
(2010/08/22)
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- Modular synthesis of chiral N-protected β-seleno amines and amides via cleavage of 2-oxazolidinones and application in palladium-catalyzed asymmetric allylic alkylation
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A set of chiral β-seleno amines have been efficiently synthesized via the ring-opening reaction of chiral N-acyl oxazolidinones by selenium nucleophiles. These compounds could be transformed into β-seleno amides by reaction with acid chlorides. The presen
- Sehnem, Jasquer A.,Vargas, Fabricio,Milani, Priscila,Nascimento, Vanessa,Braga, Antonio L.
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p. 1262 - 1268
(2008/12/22)
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- Straightforward synthesis of non-natural selenium containing amino acid derivatives and peptides
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A series of non-natural selenium-containing amino acid derivatives and peptides have been synthesized, in a flexible and modular strategy. The peptide coupling reaction between N-protected amino acids and chiral ss-seleno amines afforded the desired products in high yields. Wiley-VCH Verlag GmbH & Co. KGaA, 2005.
- Braga, Antonio L.,Luedtke, Diogo S.,Paixao, Marcio W.,Alberto, Eduardo E.,Stefani, Helio A.,Juliano, Luiz
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p. 4260 - 4264
(2007/10/03)
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- Chiral lithium amido sulfide ligands for asymmetric addition reactions of alkyllithium reagents to aldehydes
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Six chiral amino sulfides have been synthesised from the amino acids phenylalanine, phenylglycine and valine. These amino sulfides were used as chiral ligands in the asymmetric addition of n-butyllithium and metyllithium to various aldehydes at low temperatures. The highest stereoselectivities were obtained with benzaldehyde, resulting in 1-phenyl-1-pentanol and 1-phenyl-1-ethanol in enantiomeric excesses of >98.5 and 95%, respectively. These stereoselectivities were significantly higher than those induced by the ether analogues.
- Granander, Johan,Sott, Richard,Hilmersson, Goeran
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p. 439 - 447
(2007/10/03)
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- Origins of enantioselectivity with nitrogen-sulfur chelate ligands in palladium-catalyzed allylic substitution
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The reaction of 1,3-diphenyl-2-propenyl acetate (9) with dimethylmalonate to give the substitution product 10 is effectively catalyzed by Pd complexes containing chiral imine-sulfide chelate ligands derived from amino acids. The ligand of choice, (S)-N-2′-chlorobenzylidene-2-amino-3-methyl-1-thiophenylbutane (6e), prepared in only two steps from (S)-valinol, gave an ee of 94%. Because the explanation of selectivity with the majority of other nitrogen-sulfur chelate ligands in this reaction assumes the selectivity to be controlled by an electronic bias, which contradicts our results, we characterized the Pd-allyl intermediate 14 by X-ray diffraction and solution NMR. The possible mechanism of chirality transfer is discussed. The site of nucleophilic attack on the allyl ligand is not trans to the perceived better π-acceptor ligand (sulfur), which would be analogous to chiral nitrogen-phosphorus systems. This reaction occurs trans to the imine donor, and the enantioselectivity is ultimately controlled by the subtle steric environment of the chiral imine-sulfur chelate ligand, which predisposes the allyl unit of the reaction intermediate to a preferred reaction trajectory. In light of results that emphasize the power of electronic desymmetrization for chiral recognition, these results suggest that electronically dissimilar ligands may not give rise to chiral recognition through electronic dissimilarity.
- Adams, Harry,Anderson, James C.,Cubbon, Rachel,James, Daniel S.,Mathias, John P.
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p. 8256 - 8262
(2007/10/03)
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- Chiral β-amino sulfoxides. Synthesis, configurational assignment and conformational analysis based on X-ray, CD, 1H NMR and theoretical calculations
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Enantiomerically pure u and l β-amino sulfoxides have been easily obtained from the respective homochiral α-amino alcohols. The absolute configuration at the created stereogenic centre was assigned by CD spectra and by X-ray analysis. Conformational analysis of the title compounds was carried out using quantum chemical energy-geometry optimization. Thus established conformational behavior explained the strongly configuration dependent NMR spectral patterns observed for the u and l diastereomers.
- Lewanowicz,Lipinski,Siedlecka,Skarzewski,Baert
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p. 6571 - 6586
(2007/10/03)
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- New Approaches to the Synthesis of trans-Alkene Isosteres of Dipeptides
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Two new syntheses of protected dipeptide analogues bearing a trans carbon-carbon double bond in place of the amide linkage are reported.One route is a linear synthesis employing the rearrangement of an allylic selenide to a protected allylic amine.The second route is convergent and uses the Julia olefin synthesis in a key step.The latter route is fully stereocontrolled and has been used to prepare protected trans-alkene isosteres of the dipeptides TyrAla, PhePhe, LeuPhe, and LeuLeu.
- Spaltenstein, Andreas,Carpino, Philip A.,Miyake, Fumio,Hopkins, Paul B.
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p. 3759 - 3766
(2007/10/02)
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