3391-99-9Relevant academic research and scientific papers
Mechanistic implications of the enantioselective addition of alkylzinc reagents to aldehydes catalyzed by nickel complexes with α-amino amide ligands
Escorihuela, Jorge,Burguete, M. Isabel,Ujaque, Gregori,Lledós, Agustí,Luis, Santiago V.
supporting information, p. 11125 - 11136 (2016/12/07)
The enantioselective alkylation of aldehydes catalysed by nickel(ii)-complexes derived from α-amino amides was studied by means of density functional theory (DFT) and ONIOM (B3LYP:UFF) calculations. A mechanism was proposed in order to investigate the origin of enantioselectivity. The chirality-determining step for the alkylation was the formation of the intermediate complexes with the involvement of a 5/4/4-fused tricyclic transition state. The predominant products predicted theoretically were of (S)-configuration, in good agreement with experimental observations. The scope of the reaction was examined and high yields and enantioselectivities were observed for the enantioselective addition of Et2Zn and Me2Zn to aromatic and aliphatic aldehydes.
Structural insight into the aggregation of l-prolyl dipeptides and its effect on organocatalytic performance
Berdugo, Cristina,Escuder, Beatriu,Miravet, Juan F.
supporting information, p. 592 - 600 (2015/02/18)
NMR and organocatalytic studies of four dipeptides derived from l-proline are described. Results indicate that important conformational changes around the catalytic l-proline moiety are observed for free dipeptides upon changing the adjacent amino acid. Also, an aggregation process is detected as the concentration increases. The self-association of the dipeptides has been fitted to a cooperative binding model. All the compounds have been assayed as catalysts for the conjugated addition of cyclohexanone to trans-β-nitrostyrene in toluene. In agreement with the structural studies, noticeable changes in the catalytic performance are detected upon changing the catalyst concentration, as the catalyst is activated by self-aggregation. This journal is
C2 symmetrical nickel complexes derived from α-amino amides as efficient catalysts for the enantioselective addition of dialkylzinc reagents to aldehydes
Escorihuela, Jorge,Altava, Belen,Burguete, M. Isabel,Luis, Santiago V.
, p. 551 - 558 (2013/07/27)
A series of C2 symmetrical 1:2 Ni:L complexes derived from α-amino amides were studied for the enantioselective addition of dialkylzinc reagents to aldehydes. Different structural elements on the ligands seem to play an important role in determining the observed enantioselectivity. Through optimization of structure and reaction conditions, the best ligand provided secondary alcohols in excellent yields (up to 98%) and enantioselectivity of up to 99% ee for (R)-enantiomer. A transition state model has been proposed to explain the observed enantioselectivities based on computational calculations at the DFT level. Very interestingly, calculations suggest a coordination model of the aldehyde to the metal complex through association of a lone pair of the carbonyl oxygen to the hydrogen atom of an amino group.
Efficient access to enantiopure γ4-amino acids with proteinogenic side-chains and structural investigation of γ4- asn and γ4-ser in hybrid peptide helices
Jadhav, Sandip V.,Misra, Rajkumar,Singh, Sumeet K.,Gopi, Hosahudya N.
supporting information, p. 16256 - 16262 (2013/12/04)
Hybrid peptides composed of α- and β-amino acids have recently emerged as new class of peptide foldamers. Comparatively, γ- and hybrid γ-peptides composed of γ4-amino acids are less studied than their β-counterparts. However, recent investigations reveal that γ4-amino acids have a higher propensity to fold into ordered helical structures. As amino acid side-chain functional groups play a crucial role in the biological context, the objective of this study was to investigate efficient synthesis of γ4-residues with functional proteinogenic side-chains and their structural analysis in hybrid-peptide sequences. Here, the efficient and enantiopure synthesis of various N- and C-terminal free-γ4-residues, starting from the benzyl esters (COOBzl) of N-Cbz-protected (E)-α,β-unsaturated γ-amino acids through multiple hydrogenolysis and double-bond reduction in a single-pot catalytic hydrogenation is reported. The crystal conformations of eight unprotected γ4-amino acids (γ4-Val, γ4-Leu, γ4-Ile, γ4-Thr(OtBu), γ4-Tyr, γ4-Asp(OtBu), γ4- Glu(OtBu), and γ-Aib) reveals that these amino acids adopted a helix favoring gauche conformations along the central Cγi￡ Cβ bond. To study the behavior of γ4- residues with functional side chains in peptide sequences, two short hybrid γ-peptides P1 (Ac-Aib-γ4-Asn-Aib-γ4-Leu- Aib-γ4-Leu-CONH2) and P2 (Ac-Aib- γ4-Ser-Aib-γ4-Val-Aib-γ4-Val- CONH2) were designed, synthesized on solid phase, and their 12-helical conformation in single crystals were studied. Remarkably, the γ4-Asn residue in P1 facilitates the tetrameric helical aggregations through interhelical H bonding between the side-chain amide groups. Furthermore, the hydroxyl side-chain of γ4-Ser in P2 is involved in the interhelical H bonding with the backbone amide group. In addition, the analysis of 87 γ4-residues in peptide single-crystals reveal that the γ4-residues in 12-helices are more ordered as compared with the 10/12- and 12/14-helices. Copyright
Di-Amido Gellant For Use In Consumer Product Compositions
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Page/Page column 12, (2011/10/04)
The invention is to di-amido gellant that are suitable for use in consumer product compositions.
Amino acid based low-molecular-weight tris(bis-amido) organogelators
Samai, Suman,Dey, Joykrishna,Biradha, Kumar
scheme or table, p. 2121 - 2126 (2012/05/04)
Two new amino acid based low-molecular-mass organic gelators were designed, synthesized, and examined for their ability to gelate various organic solvents. The gelator molecules were found to aggregate via N-H...O hydrogen bonding to form an interwinding 3D network which immobilized a large number of organic solvents. Among the different organic solvents used in the gelation study mesitylene is found to be the best solvent. The microstructure of organogels was studied with FESEM and optical micrographs. The involvement of hydrogen bonding in the aggregation of the gelator molecule was studied using temperature dependent 1H NMR. The obtained organogels were found to exhibit significant mechanical strength.
Convenient synthesis of N-hydroxysuccinimide esters from carboxylic acids using triphosgene
Kim, Misoo,Han, Ki-Jong
experimental part, p. 4467 - 4472 (2010/05/01)
A simple and convenient method for the synthesis of N-hydroxysuccinimide ester is developed using triphosgene as an acid activator. Several aromatic and aliphatic N-hydroxysuccinimide esters are prepared from their corresponding carboxylic acids at room temperature in good yields in a rapid process using triphosgene. Some of the major advantages are mild conditions, good yields, and easy operation.
Enantioselective nickel-catalyzed conjugate addition of dialkylzinc to chalcones using chiral α-amino amides
Escorihuela, Jorge,Burguete, M. Isabel,Luis, Santiago V.
scheme or table, p. 6885 - 6888 (2009/04/07)
A series of α-amino amides derived from natural amino acids (alanine, valine, phenylalanine, isoleucine, and phenylglycine) have been synthesized and fully characterized. Their Ni(II) complexes prepared from Ni(acac)2 catalyze the enantioselective conjugate addition of diethylzinc to chalcones in high yields and in good enantioselectivities (up to 84%). The side chain of the amino acid and the substituents in the amide nitrogen govern the enantioselectivity of the catalytic process.
Synthesis of potent water-soluble tissue transglutaminase inhibitors
Griffin, Martin,Mongeot, Alexandre,Collighan, Russell,Saint, Robert E.,Jones, Richard A.,Coutts, Ian G.C.,Rathbone, Daniel L.
scheme or table, p. 5559 - 5562 (2009/05/30)
Dipeptide-based sulfonium peptidylmethylketones derived from 6-diazo-5-oxo-l-norleucine (DON) have been investigated as potential water-soluble inhibitors of extracellular transglutaminase. The lead compounds were prepared in four steps and exhibited pote
