Norbiotinamine is an alternative to biotin. Norbiotinamine can be coupled with a carboxylic group of amino acids to give inverse peptides, having the amide linkage oriented in the opposite direction.In Vitro: In order to couple biotin to amino acids, reaction has to be with an amino group. An example is biocytin (biotin lysine). However, Norbiotinamine could be coupled with a carboxylic group of amino acids to give inverse peptides, having the amide linkage oriented in the opposite direction. As an example, Norbiotinamine is coupled with the NHS ester of N-Boc-glutamic acid γ-benzyl ester. The resulting norbiotinylamide of γglutamic acid (VII), obtained after deprotection, is similar to biocytin, but it has a shorter aliphatic chain and an inverted amide bond.