Modular Monodentate Phosphoramidite Ligands for Rhodium-Catalyzed Enantioselective Hydrogenation
作者:Yan Liu、Kuiling Ding
DOI:10.1021/ja052749l
日期:2005.8.1
A new class of monodentate phosphoramidite ligands (DpenPhos) has been developed on the basis of the modular concept for Rh(I)-catalyzed asymmetric hydrogenations of a variety of olefin derivatives, affording the corresponding optically active compounds in excellent yields and enantioselectivities. The ligands have the advantages of facile preparation, tunable structure, and broad scope of substrates
Asymmetric chemoenzymatic synthesis of N-acetyl-α-amino esters based on lipase-catalyzed kinetic resolutions through interesterification reactions
作者:Marcos Reinaldo da Silva、Marcos Carlos de Mattos、Maria da Conceição Ferreira de Oliveira、Telma Leda Gomes de Lemos、Nágila Maria Pontes Silva Ricardo、Gonzalo de Gonzalo、Iván Lavandera、Vicente Gotor-Fernández、Vicente Gotor
DOI:10.1016/j.tet.2014.02.012
日期:2014.4
transfer catalysts, this compound reacted with several alkyl halides, being benzyltributylammonium chloride identified as the best one for the production of a series of quaternary amino acids in moderate to excellent yields (52–95%). Then, the corresponding N-acetyl-phenylalanine methyl and allyl ester derivatives were obtained through acidic hydrolysis, esterification, and N-acetylation. Rhizomucor miehei
Damage of aromatic amino acids by the atmospheric free radical oxidant NO3˙ in the presence of NO2˙, N2O4, O3 and O2
作者:Catrin Goeschen、Natalia Wibowo、Jonathan M. White、Uta Wille
DOI:10.1039/c0ob01186j
日期:——
Analysis of the products formed in the reaction of NO3Ë with the N- and C-protected aromatic amino acids 1â5, which was performed under conditions that simulate exposure of biosurfaces to environmental pollutants, revealed insight how this important atmospheric free-radical oxidant can cause irreversible damage. In general, NO3Ë induced electron transfer at the aromatic ring is the exclusive initial pathway in a multi-step sequence, which ultimately leads to nitroaromatic compounds. In the reaction of NO3Ë with tryptophan 5 tricyclic products 12 and 13 are formed through an intramolecular, oxidative cyclization involving the amide moiety. In addition to this, strong indication for formation of N-nitrosamides was obtained, which likely result from reaction with N2O4 through an independent non-radical pathway.
New monodentate chiral phosphonites were synthesized from enantiomerically pure 1,1'-spirobiindane7,7'-diol. The phosphonites 2 were efficient ligands for the Rh-catalyzed asymmetric hydrogenation of alpha- and beta-dehydroamino acid derivatives, providing the amino acids in high enantioselectivities. The study of electronic effect showed that the electron-withdrawing substitutent on the P-phenyl ring of the phosphonite ligand dramatically decreased both the reactivity and enantioselectivity of the ligand.
Diaza-Crown Ether-Bridged Chiral Diphosphoramidite Ligands: Synthesis and Applications in Asymmetric Catalysis
作者:Yier Luo、Guanghui Ouyang、Yuping Tang、Yan-Mei He、Qing-Hua Fan
DOI:10.1021/acs.joc.0c00223
日期:2020.6.19
A small library of diaza-crown ether-bridged chiral diphosphoramidite ligands was prepared. In the rhodium-catalyzed asymmetric hydrogenation and hydroformylation reactions, these ligands exhibited distinct properties in catalytic activity and/or enantioselectivity. Hydrogenated products with opposite absolute configurations could be obtained in high yields with excellent ee values by utilizing (S