title: Synthesis of Quaternary-Carbon-Containing β2,2-Amino Acids by the RhI-Catalyzed Enantioselective Arylation of α-Substituted β-Nitroacrylates.
abstract: An enantioselective RhI-catalyzed conjugate addition reaction of α-substituted β-nitroacrylates with various arylboronic acids by using chiral RhIdiene catalysts is described for the first time. The addition reaction proceeds under mild conditions in a range of common organic solvents and additives, and it affords the corresponding quaternary-carbon-containing α,α-disubstituted β-nitropropionate products in up to 63 % yield and 99 % ee. Reaction of either (E)- or (Z)-β-nitroacrylates provided the same enantiomer of the product, and a range of esters and aryl groups were tolerated. To demonstrate the utility of the method, ethyl (R)-1,1-methyl-1-phenyl-3-nitropropionate, prepared herein, was converted to the non-proteinogenic β2,2-amino acid, (R)-2-(aminomethyl)-2-phenylpropanoic acid, and to the β2,2-lactam, (R)-3-methyl-3-phenylazetidin-2-one. In addition, a tripeptide, which comprised l-phenylalanine, l-alanine, and β2,2-amino acid 7, was also synthesized.
authors: Department of Chemistry, National (Taiwan) Normal University, No. 88, Section 4, Tingzhou Road, Taipei, 11677, Taiwan.
authors: Jo-Hsuan
authors: JH
authors: Fang
authors: Department of Chemistry, National (Taiwan) Normal University, No. 88, Section 4, Tingzhou Road, Taipei, 11677, Taiwan.
authors: Jia-Hong
authors: JH
authors: Jian
authors: Department of Chemistry, National (Taiwan) Normal University, No. 88, Section 4, Tingzhou Road, Taipei, 11677, Taiwan.
authors: Hao-Ching
authors: HC
authors: Chang
authors: Department of Chemistry, National (Taiwan) Normal University, No. 88, Section 4, Tingzhou Road, Taipei, 11677, Taiwan.
authors: Ting-Shen
authors: TS
authors: Kuo
authors: Department of Chemistry, National (Taiwan) Normal University, No. 88, Section 4, Tingzhou Road, Taipei, 11677, Taiwan.
authors: Way-Zen
authors: WZ
authors: Lee
authors: Department of Chemistry, National (Taiwan) Normal University, No. 88, Section 4, Tingzhou Road, Taipei, 11677, Taiwan.
authors: Ping-Yu
authors: PY
authors: Wu
authors: Department of Chemistry, National (Taiwan) Normal University, No. 88, Section 4, Tingzhou Road, Taipei, 11677, Taiwan.
authors: Hsyueh-Liang
authors: HL
authors: Wu
keywords: amino acids; asymmetric catalysis; conjugate addition; diene ligands; rhodium