Enantioselectivity Enhancement in the Deacylation of N-Acyl Amino Acid Esters by Vesicular Systems of Long Chain Dipeptide Nucleophiles and a Cationic Double Chain Surfactant

Abstract

Abstract The enantioselective deacylation of short chain and long chain N-acyl amino acid p-nitrophenyl esters, CH3(CH2)nCONH\overset*CH(R)–CO2C6H4NO2-p (R=C6H5CH2, (CH3)2CHCH2, CH3; n=0, 8, 12), was carried out at 4–25°C (pH 7.68) with the vesicular systems composed of N,N-didodecyl-N,Ndimethylammonium bromide and long chain nucleophiles, Nα-dodecanoyl-l-histidine, Nα-(N-dodecanoyl-l-leucyl)-l-histidine(3a), Nα-(N-dodecanoyl-l-phenylalanyl)-l-histidine (3b), and N-(Nα-dodecanoyl-l-histidyl)-l-leucine (3c). Both the deacylation rate and the enantioselectivity were the largest in the deacylation of the substrates possessing a long N-acyl chain (n=8) with the efficient dipeptide nucleophiles (3a and 3b) including the l-histidine moiety in their terminal position, and the neighboring amino acid binding to the l-histidine in 3a, 3b, and/or 3c was found to play an important role in the enhancement of enantioselectivity. The lowering of the reaction temperature decreased the deacylation rate and increased the enantioselectivity. The maximum enantiomer rate ratio of 24.5 was obtained in the deacylation of p-nitrophenyl N-dodecanoylphenylalaninates with the dipeptide nucleophile 3b. The characteristic features of the present reaction are discussed on the basis of kinetic parameters (binding constants and activation parameters) and isokinetic relationships.