Chemical synthesis and enzymatic, stereoselective hydrolysis of a functionalized dihydropyrimidine for the synthesis of β-amino acids

A novel substrate, 6-(4-nitrophenyl)dihydropyrimidine-2,4(1H,3H)-dione (pNO2PheDU), was chemically synthesized and analytically verified for the potential biocatalytic synthesis of enantiopure β-amino acids. The hydantoinase (EC 3.5.2.2) from Arthrobacter crystallopoietes DSM20117 was chosen to prove the enzymatic hydrolysis of this substrate, since previous investigations showed activities of this enzyme toward 6-monosubstituted dihydrouracils. Whole cell biotransformations with recombinant Escherichia coli expressing the hydantoinase showed degradation of pNO2PheDU. Additionally, the corresponding N-carbamoyl-β-amino acid (NCarbpNO2 βPhe) was chemically synthesized, an HPLC-method with chiral stationary phases for detection of this product was established and thus (S)-enantioselectivity toward pNO2PheDU has been shown. Consequently this novel substrate is a potential precursor for the enantiopure β-amino acid para-nitro-β-phenylalanine (pNO2 βPhe).