Carbocyclic α-amino acids: asymmetric Strecker synthesis of a series of 2-alkylated 1-aminocyclopentanecarboxylic acids
作者:Judith Wede、Franz-J Volk、August W Frahm
DOI:10.1016/s0957-4166(00)00284-6
日期:2000.8
A series of 12 carbocyclic alpha-amino acids has been prepared from four different racemic 2-alkylated cyclopentanones and (R)-1-phenylethylamine as the chiral auxiliary by means of an asymmetric Strecker synthesis. The stereoselectivity was influenced by solvent, temperature and size of the substituent at the 2-position of the cyclopentanones. For the methyl and ethyl substituted amino acids all four possible stereoisomers could be obtained, whereas for the isopropyl and tertiary butyl compounds an unexpected side reaction prohibited the isolation of the cis configured amino acids. The 1,3-induction mechanism observed for the kinetically controlled alpha-amino nitrile formation in the 2-methyl and 2-ethyl series was overlayed by a 1,2-induction in the respective 2-isopropyl and 2-tertiary butyl series. (C) 2000 Elsevier Science Ltd. All rights reserved.
Stereoselective Michael additions on α-aminoacrylates as the key step to an<scp>l</scp>-Oic analogue bearing a quaternary stereocenter
作者:Federico Maria Cecchinelli、Giuseppe Celentano、Alessandra Puglisi、Nicoletta Gaggero
DOI:10.1039/c9ob02084e
日期:——
A novel, highly stereoselective route for pharmaceutically relevant octahydroindole-2-carboxylates bearing a quaternarystereocenter has been developed. The key chiral intermediates 3 have been prepared in good yields and enantiomeric excesses up to 98%. A broad substrate range has been tolerated under the reaction conditions.