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

[摘要]：Biotransformations of a no. of racemic b-hydroxy and b-amino nitrile derivs. were studied using Rhodococcus erythropolis AJ270, the nitrile hydratase and amidase-contg. 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 b-hydroxy and b-amino alkanenitriles gave low yields of amide and acid products of very low enantiomeric purity, introduction of a simple benzyl protection group on the b-hydroxy and b-amino of nitrile substrates led to the formation of highly enantioenriched b-benzyloxy and b-benzylamino amides and acids in almost quant. yield. The easy protection and deprotection operations, high chem. yield, and excellent enantioselectivity render the nitrile biotransformation a useful protocol in the synthesis of enantiopure b-hydroxy and b-amino acids.

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