Radical addition to oximeethers for asymmetric synthesis of β-amino acid derivatives

Abstract

The diastereoselective alkyl radical addition to chiral oxime ethers was studied with a view to preparing enantiomerically pure α,β-dialkyl-β-amino acid derivatives. The phase transfer-catalyzed alkylation of Oppolzer's camphorsultam derivative of oxime ether proceeded smoothly to give the alkylated N-(β-oximino)acyl derivatives. In the presence of BF₃·OEt₂, radical addition to the oxime ethers proceeded using triethylborane as the radical initiator to give α,β-dialkyl-β-amino acid derivatives with excellent diastereoselectivity.