α-Azido carboxylic acids have recently emerged as versatile N-protected equivalents for α-amino acids, especially valuable when the sterically hindered Cα-dialkylated α-amino acids have to be incorporated. Unsymmetrically substituted Cα-dialkylated α-azido carboxylic acids can be obtained in enantiomerically pure form by enzymatic resolution of α-azido carboxamides. A l-amidase from Ochrobactrum anthropi NCIMB 40321 accepts 2-azido-2,4-dimethylpentanamide as the substrate and provides both the corresponding S-configured α-azido carboxylic acid and the R-configured α-azido carboxamide in excellent enantiomeric purity. The former is a valuable synthetic precursor of α-methylleucine [(α-Me)Leu] in peptide synthesis, as demonstrated by the successful synthesis of a (α-Me)Leu containing efrapeptin C analogue.
α-
叠氮羧酸最近被提出作为多功能的N保护等同物,适用于
α-氨基酸,尤其在需要引入立体障碍的Cα-二烷基化
α-氨基酸时极为宝贵。通过对α-
叠氮羧酰胺的酶促分离,可以获得不对称取代的Cα-二烷基化α-
叠氮羧酸的对映纯形式。来自Ochrobactrum anthropi NCIMB 40321的l-酰胺酶以2-
叠氮-2,4-二甲基戊酰胺为底物,分别提供对应的S构型α-
叠氮羧酸和R构型α-
叠氮羧酰胺,且具有优异的对映体纯度。这前者是合成α-甲基亮
氨酸[(α-Me)Leu]在肽合成中的有价值合成前体,成功合成了含有(α-Me)Leu的efrapeptin C类似物。