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
合成了一组具有扩展的芳基或苄基型基团的第二代DBFOX配体。必需的氨基醇可以商购(DBFOX / Bn)或通过Sharpless不对称氨基羟基化(DBFOX / Nap,DBFOX / t-BuPh,DBFOX / Pip)或相转移催化的不对称烷基化(DBFOX / MeNap)来构建。评估了配体与Mg(NTf2)2的配合物作为α,β-不饱和α-硝基酰胺和酯类对映选择性自由基共轭物添加的促进剂。相对于先前由DBFOX / Ph介导的添加,使用DBFOX / Nap配体的反应表现出改进的对映选择性。但是,非对映异构体比例的相对适度增加表明我们的底物-路易斯酸结合模型