Nitrile Biotransformations for the Synthesis of Highly Enantioenriched β-Hydroxy and β-Amino Acid and Amide Derivatives: A General and Simple but Powerful and Efficient Benzyl Protection Strategy To Increase Enantioselectivity of the Amidase

Abstract

Biotransformations of a number of racemic beta-hydroxy and beta-amino nitrile derivatives were studied using Rhodococcus erythropolis AJ270, the nitrile hydratase and amidase-containing microbial whole cell catalyst, under very mild conditions. The overall enantioselectivity of nitrile biotransformations was governed predominantly by the amidase whose enantioselectivity was switched on remarkably by an O- and a N-benzyl protection group of the substrates. While biotransformations of beta-hydroxy and beta-amino alkanenitriles gave low yields of amide and acid products of very low enantiomeric purity, introduction of a simple benzyl protection group on the beta-hydroxy and beta-amino of nitrile substrates led to the formation of highly enantioenriched beta-benzyloxy and beta-benzylamino amides and acids in almost quantitative yield. The easy protection and deprotection operations, high chemical yield, and excellent enantioselectivity render the nitrile biotransformation a useful protocol in the synthesis of enantiopure beta-hydroxy and beta-amino acids.

Overexpression of a recombinant amidase in a complex auto-inducing culture: purification, biochemical characterization, and regio- and stereoselectivity

“…Two hundred microliters of isopropyl alcohol was added to resolve the precipitation after a process of ether extraction (700 ll) and blowdrying. Five microliters of the solution was used in the high-performance liquid chromatography (HPLC) assay as previously reported [23,24,44]. All products were characterized by their spectral data.…”

“…Substrate engineering, as an alternative method, seems to be useful in improving the efficiency and selectivity of biocatalysis. Ma et al [22][23][24] found that using the O-benzyl and N-benzyl protection/ docking method dramatically enhanced the enantioselectivity of biotransformations. The results of the current study indicate that, compared with free b-hydroxy and b-amino phenylpropionamides, the enzyme that catalyzed the hydrolysis of O-benzyl and N-benzyl phenylpropionamides afforded remarkably high enantioselective biotransformations.…”

“…The results of the current study indicate that, compared with free b-hydroxy and b-amino phenylpropionamides, the enzyme that catalyzed the hydrolysis of O-benzyl and N-benzyl phenylpropionamides afforded remarkably high enantioselective biotransformations. The remote chiral recognition mechanism, which asserts that the chiral recognition site of the enzyme may be located far from the catalytic center, can explain this phenomenon [23]. Considering the easy protection and deprotection operations, this enzyme provides good resolution for the biosynthesis of compounds with free b-hydroxy and b-amino amides and acids, as well as their derivatives.…”

“…Nitriles are successively transformed by nitrile hydratase and amidase into the corresponding amides and carboxylic acid derivatives. Rhodococcus erythropolis AJ270, isolated from a disused industrial site on the banks of the River Tyne in northeast England [1,2], hydrates numerous nitriles to the corresponding amides and carboxylic acids with high regio-and stereoselectivity [23,35,41,42]. Although nitrile hydratase shows enantioselectivity with some substrates, such enantioselectivity, is largely due to amidase [43].…”

Enantioselective hydrolysis of (R)-2, 2-dimethylcyclopropane carboxamide by immobilized cells of an R-amidase-producing bacterium, Delftia tsuruhatensis CCTCC M 205114, on an alginate capsule carrier

“…Production of economically important chiral carboxyl acid and its amide derivatives by biotransformation of nitrile using nitrile-converting enzymes (nitrile hydratase, amidase and nitrilase) has become a promising chiral synthesis method [3,5,14,15,[18][19][20]33]. With the ability to hydrolyze amides to corresponding optical pure compounds with high enantioselectivity, mild reaction conditions and environmental compatibility, amidases (EC 3.5.1.4) have been intensively studied [2,4,7,8,10,12,13,16,17,21,22,26,30].…”