120125-43-1Relevant articles and documents
syn-Selective Michael Reaction of α-Branched Aryl Acetaldehydes with Nitroolefins Promoted by Squaric Amino Acid Derived Bifunctional Br?nsted Bases
Campano, Teresa E.,García-Urricelqui, Ane,Mielgo, Antonia,Palomo, Claudio,de Cózar, Abel
supporting information, p. 3604 - 3612 (2021/07/26)
Here we describe a direct access to 2,2,3-trisubstituted syn γ-nitroaldehydes by addition of α-branched aryl acetaldehydes to nitroolefins promoted by a cinchona based squaric acid-derived amino acid peptide. Different α-methyl arylacetaldehydes react with β-aromatic and β-alkyl nitroolefins to afford the Michael adducts in high enantioselectivity and syn-selectivity. NMR experiments and DFT calculations predict the reaction to occur through the intermediacy of E-enolate. The interaction between the substrates and the catalyst follows Pápai's model, wherein an intramolecular H-bond interaction in the catalyst between the NH group of one of the tert-leucines and the squaramide oxygen seems to be key for discrimination of the corresponding reaction transition states.
A new type of L-Tertiary leucine-derived ligand: Synthesis and application in Cu(II)-catalyzed asymmetric Henry reactions
Cai, Zedong,Lan, Ting,Ma, Pengfei,Zhang, Jingfang,Yang, Qingqing,He, Wei
, (2019/08/08)
A new series of Schiff bases derived from amino acids were developed as chiral ligands for Cu(II)-catalyzed asymmetric Henry reactions. The optimum ligand 7d exhibited outstanding catalytic efficiency in the Cu(II)-catalyzed asymmetric Henry additions of four nitroalkanes to different kinds of aldehydes to produce 76 desired adducts in high yields (up to 96%) with excellent enantioselectivities, up to 99% enantiomeric excess (ee).
Fmoc-based synthesis of peptide thioesters for native chemical ligation employing a tert -butyl thiol linker
Raz, Richard,Rademann, Joerg
, p. 1606 - 1609 (2011/05/12)
tert-Butyl thioesters display an astonishing stability toward secondary amines in basic milieu, in contrast to other alkyl and aryl thioesters. Exploiting this enhanced stability, peptide thioesters were synthesized in a direct manner, applying a tert-butyl thiol linker for Fmoc-based solid-phase peptide synthesis.
