Highly Diastereoselective Radical Addition to Oxime Ethers: Asymmetric Synthesis of β-Amino Acids
摘要:
[GRAPHICS]Highly diastereoselective alkyl radical addition to Oppolzer's camphorsultam derivatives of oxime ethers provided a convenient method for preparing the enantiomerically pure alpha,beta-dialkyl-beta-amino acids. The phase-transfer-catalyzed alkylation was an excellent method for the selective monoalkylation of the N-(beta-oximino)acyl derivative of Oppolzer's sultam, with no detection of dialkylated products. In the presence of BF3. OEt2, the carbon radical addition to the oxime ethers proceeded smoothly to give the alpha,beta-dialkyl-beta-amino acid derivatives with excellent diastereoselectivity.