D. Seebach, Robert Häner, Thomas Vettiger
Sep 23, 1987
Citations
0
Influential Citations
28
Citations
Journal
Helvetica Chimica Acta
Abstract
Nucleophilic Ring Opening of Aryl α-Nitrocyclopropanecarboxylates with Sterically Protected but Electronically Effective Carbonyl and Nitro Group. A New Principle of α-Amino Acid Synthesis (2-Aminobutanoic Acid a4-Synthon) The readily available 2,4,6-tri(tert-butyl)-and 2,6-di(tert-butyl)-4-methoxypahenol esters 2 of α-nitrocyclo-propanecarboxaylic acid ring opening with C-, N-, O-, and S-nucleophiles (cyanide, malonate, azide, anilines, alkoxides, phenoxides, thiolates) in DMF or alcohol solvents (80–95% yield). The products 6–14 are 2-nitrobutanoates with the newly introduced substituent in the 4-position. Reduction of the NO2 group with Zn/AcOH/Ac2O gives N-acetyl-α-amino acid esters 16–22 (40–90% yield). Subsequent oxidative cleavage (H2O2/HCOOH) of The p-methoxy-phenyl esters 18 and 20 produces free amino acids (65% 23 and 67% 24, respectively). Thus, the nitro ester 2 corresponds to a 2-aminobutanoic-acid a4-synthon, it is a ‘homo-Michael acceptor’ producing γ-substituted α-amino acids.