Abstract
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.
Key words
azides - bioorganic chemistry - enantiomeric resolution - enzymes - peptides
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