Biocatalytic concepts for synthesizing amine bulk chemicals: recent approaches towards linear and cyclic aliphatic primary amines and -substituted derivatives thereof

In this mini-review, an overview about various developed strategies for accessing industrially relevant primary n-alkyl amines via reductive amination by means of amine dehydrogenases as well as transaminases is given. Such transformations were combined with in situ cofactor recycling methodologies avoiding the need for addition of external stoichiometric amounts of organic co-substrates. These methods comprise the application of natural photosynthesis with algae when using carbonyl compounds as substrates as well as the utilization of alcohols as substrates in combination with self-sufficient biocatalytic systems. As such a feature is of utmost importance for large-scale biotransformations in the field of bulk chemicals, which represent high-volume but low-price chemicals, the achievements open up a perspective for biocatalysis also in the area of commodity chemicals. Besides approaches to n-alkyl amines and cyclohexylamine, recently also biocatalytic cascades towards n-alkyl amines bearing functionalities in the -position such as a carboxylic acid ester or amino group were reported. It is noteworthy that for -aminolauric acid, such a process has already been demonstrated on pilot plant scale.