Diastereoselective Conjugate Addition to (+)-Camphorsulfonic Acid Derived Nitroalkenes: Synthesis of alpha-Hydroxy and alpha-Amino Acids.
Diastereoselective tandem conjugate addition of both oxygen- and nitrogen-centered nucleophiles to the novel (1S)-10-camphorsulfonic acid derived nitroalkenes 9, 10, and 11 and ozonolysis gave the alpha-hydroxy and alpha-amino thiol acid derivatives 12, 13, and 14. In all cases, the (R)-diastereomer was formed as the major component albeit with only modest levels of selectivity (33-71% de). The structures of the products and the stereochemistry of the Michael addition step were unequivocally established by X-ray crystallographic studies of nitroalkenes 9 and 10 and (2S)-12c and (2R)-13a and by alternative syntheses from (S)-alanine, (S)-valine, and ethyl (S)-lactate.
Barrett
Anthony G. M.
AG
Department of Chemistry, Imperial College, South Kensington, London, SW7 2AY, UK and Department of Chemistry, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60208.
Braddock
D. Christopher
DC
Christian
Paul W. N.
PW
Pilipauskas
Daniel
D
White
Andrew J. P.
AJ
Williams
David J.
DJ