Penicillin G acylase-mediated kinetic resolution of racemic 1-(N-acylamino)alkylphosphonic and 1-(N-acylamino)alkylphosphinic acids and their esters

• Penicillin G acylase-mediated kinetic resolution of N-acylated phosphorus analogues of α-amino acids was developed.
• The initial hydrolytic deacylation rates rapidly decrease with the increasing steric effect of the substituent at the α-position.
• Bulky substituents at phosphorus hinder the enzymatic hydrolysis to a much lesser degree.
• Penicillin G acylase exhibited stereochemical preference for the (R)-substrate.

Extensive studies on the penicillin G acylase-mediated kinetic resolution of N-acylated 1-aminoalkylphosphonic and 1-aminoalkylphosphinic acids as well as their esters were carried out to recognise the relationships between the substrate structure, reaction conditions, and the enzymatic hydrolytic deacylation efficiency and stereoselectivity. Reactivity of 1-(N-acylamino)alkylphosphonic and 1-(N-acylamino)alkylphosphinic acids and their esters in the penicillin G acylase-mediated hydrolytic deacylation reaction depends strongly on the kind of their N-acyl group, with high preference to the hydrolytic splitting of the N-phenylacetyl moiety. The initial hydrolysis rates of 1-(N-phenylacetylamino)alkylphosphonic acid dimethyl esters 2 are mostly distinctly lower in comparison with the corresponding free acids 3 and rapidly decrease with the increasing steric effect of the substituent at the α-position. In contrary to the substituents at the α-carbon, bulky substituents at the phosphorus hinder the enzymatic hydrolysis to a much lesser degree. The penicillin G acylase-mediated stereospecific hydrolysis of N-acyl group of both racemic 1-(N-acylamino)alkylphosphonic acids 3 and their dimethyl esters 2 proved to be, in most cases, a highly effective method for the kinetic resolution of these compounds. High enzyme enantioselectivity E-values exceeding 100, or synthetically useful E-values exceeding 20 (in two cases) were obtained for the N-acylated phosphonic acid analogues of alanine, phenylalanine, valine, leucine, and asparagine, as well as for their dimethyl esters, with the exception of the dimethyl ester of phosphonic analogue of valine 2e, that E-value was low (E = 1.2). Also for the N-acylated H-phosphinic acid analogues of alanine, as well as phenylphosphinic acid analogue of alanine, high enzyme enantioselectivity values exceeding 100 were obtained. In contrary, E-values for both diastereomers of ethyl ester of phenylphosphinic analogue of alanine 2k were low (E = 7 and 13). For the all accomplished assignments penicillin G acylase exhibited stereochemical preference for the (R)-substrate.

Figure optionsDownload as PowerPoint slide