Elimination Of Equilibrium In A Single-enzyme Cascade Using ?-transaminase

In our daily life,chirality is closely linked to us.It involves many aspects such as pharmaceuticals,agrochemicals,chemical,and life et al.Chiral amines are pivotal intermediates and key building blocks for the development of a plethora of biologically active compounds,including industrial-scale pharmaceuticals and agrochemicals,and play a very important role in these industries.The chiral stereo configuration of phenylethylamine(PEA)is optically active,which is widely used as a chiral resolving agent to resolve organic acids.It is also widely used as a chiral auxiliary,as well as a synthesis raw material for many chiral compounds.PEA is mainly obtained through kinetic resolution and asymmetric synthesis.(R)-3-amino-1-butanol is an important intermediate in the synthesis of anti-HIV inhibitor dolutegravir.(R)-3-amino-1-butanol can also be used as an intermediate for the synthesis of carbepenem antimicrobial.Therefore,it is of great significance to research the synthesis of(R)-3-amino-1-butanol.In the method of synthesizing chiral amines,the asymmetric synthesis of chiral amine using co-transaminase has been widely used by researchers due to its advantages,for instance high conversion rate of the reaction substrate,simple reaction process.Besides,resulting in optical purity chiral amines are also key to industrial applications.However,by this method,there is a problem of equilibrium shift,and the product amine and by-product ketone will inhibit the activity of the enzyme and affect the positive shift of the reaction equilibrium.Therefore,the elimination of the problem of balanced mobility and the search for a green and simple synthetic method that can achieve higher conversion rates and stereoselectivity are difficulties which are urgently needed to be resolved.This paper presents a green method for the synthesis of(R)-and(S)-?-phenethylamine with high conversion and high ee values.We describe a highly efficient one-enzyme procedure using ?-transaminase in the absence of expensive cofactor(NAD(P)H)-dependent enzymes used for by-product removal process.The aromatic amino donor benzylamine,enabling its acceptance by transaminases with either(R)-or(S)-enantioselectivity was used,allowing reactions to proceed in excellent conversions of 99%and>99%ees using only 3 equivalents of the amino donor.During transamination reaction,the generated co-product aldehyde was irreversibly converted to its corresponding carboxylic acid assisted by aerobic oxidation with 1 atmospheric of oxygen,therefore equilibrium was successfully pushed to product side.The aerobic oxidation promoted transamination,and the corresponding method was compatible with a wide spectrum of ?-transaminases.The amino donor used here is easily and commercially obtainable,and is suitable for low-cost and scalable preparations,representing a promising pathway for clean synthesis of high value-added chiral amines.This paper also proposes a method for synthesizing(R)-3-amino-1-butanol under a dual enzyme system.We describe a highly efficient procedure using ?-transaminase and carbonyl reductase in the absence of expensive cofactor(NAD(P)H)-dependent enzymes used for by-product removal process.Racemic a-phenylethylamine was used as the amino donor and 4-hydroxy-2-butanone was used as the substrate for the reaction:a.?-transaminase and carbonyl reductase cascade reactions;b.Whole cell reaction after culture of both species.After transaminase catalyzes the transfer of amine groups,chiral amines are obtained,and by-product acetophenone is converted into chiral alcohol compounds with high optical purity by carbonyl reductase,which removes the reaction balance and increases the product's high added value.