A versatile access to optically active α-branched Ï-amino acids 8 and 9 and corresponding lactams 11 was developed allowing the synthesis of either enantiomer of these products. This asymmetric synthesis is based on amino alcohols 3 as chiral auxiliaries, which were converted to 2-(Ï-benzenesulfonylaminoalkyl)oxazolines 4 by reaction with Ï-amino-imido esters 2 or derivatives of lactams 1. The 2-(Ï-benzenesulfonylaminoalkyl)oxazolines 4 were deprotonated by LDA and α-alkylated by alkyl halides 5. Final hydrolytic cleavage of the oxazoline ring afforded the amino acids 8 and 9 or lactams 11. The method does not follow Meyers model of α-alkylation of 2-alkyloxazolines and requires BEt3 as additive in order to achieve complete stereoselectivity.
我们开发了一种通用的方法,用于光学活性β-支链-
氨基酸8和9以及相应的内酰胺11,从而能够合成这些产品的对映体。这种不对称合成基于
氨基醇3作为手性助剂,通过与β-
氨基-
亚胺酯2或内酰胺1的衍
生物反应转化为2-(β-苯磺酰
氨基烷基)
恶唑啉4。2-(β-苯磺酰
氨基烷基)
恶唑啉4通过
LDA脱质子化,并通过烷基卤化物5进行β-烷基化。最终通过
水解裂解
恶唑啉环得到
氨基酸8和9或内酰胺11。该方法不遵循2-烷基
恶唑啉的β-烷基化Meyers模型,需要添加BEt3以实现完全的立体选择性。