Synthesis of beta-substituted alpha-amino acids via Lewis acid promoted radical conjugate additions to alpha,beta-unsaturated alpha-nitro esters and amides.
[reaction: see text] Beta-substituted alpha,beta-unsaturated alpha-nitro esters and amides undergo radical conjugate additions when treated with an appropriate Lewis acid. Deuterium studies revealed that the acidic alpha-stereocenter of the alpha-nitro ester products does not racemize under strictly controlled workup conditions. The alpha-nitro amides did racemize significantly during chromatography, but this could be greatly minimized by subjecting the crude adducts to subsequent transformations. The conjugate addition products can be elaborated into beta-substituted alpha-amino acids in two simple steps.
Srikanth
G S C
GS
Department of Chemistry and Biochemistry, Brigham Young University, Provo, Utah 84602, USA.
Castle
Steven L
SL
D000143:Acids / Q000737:chemistry; D000577:Amides / Q000737:chemistry*; D000596:Amino Acids / Q000138:chemical synthesis* / Q000737:chemistry*; D004952:Esters / Q000737:chemistry*; D005609:Free Radicals / Q000737:chemistry; D009682:Magnetic Resonance Spectroscopy; D015394:Molecular Structure; D009566:Nitrates / Q000737:chemistry*
D000143:Acids; D000577:Amides; D000596:Amino Acids; D004952:Esters; D005609:Free Radicals; D009566:Nitrates