Second-Generation DBFOX Ligands for the Synthesis of β-Substituted α-Amino Acids via Enantioselective Radical Conjugate Additions
作者:Biplab Banerjee、Steven G. Capps、Junghoon Kang、Joshua W. Robinson、Steven L. Castle
DOI:10.1021/jo801721z
日期:2008.11.21
asymmetric aminohydroxylation (DBFOX/Nap, DBFOX/ t-BuPh, DBFOX/Pip) or phase-transfer-catalyzed asymmetric alkylation (DBFOX/MeNap). Complexes of the ligands with Mg(NTf2)2 were evaluated as promoters of enantioselective radical conjugate additions to alpha,beta-unsaturated alpha-nitro amides and esters. Reactions employing the DBFOX/Nap ligand exhibited improved enantioselectivity relative to previously
Synthesis of β-Substituted α-Amino Acids via Lewis Acid Promoted Enantioselective Radical Conjugate Additions
作者:Liwen He、G. S. C. Srikanth、Steven L. Castle
DOI:10.1021/jo051334f
日期:2005.9.1
Lewisacid promoted radicalconjugateadditions to β-substituted α,β-unsaturated α-nitro esters and amides were investigated. With achiral Lewisacids, there was competition between the desired radicalconjugateaddition and undesired alkene reduction mediated by Bu3SnH. Zinc Lewisacids provided the greatest amounts of addition products with both substrate classes. Studies with Bu3SnD indicated that