Enzymatic resolution for the preparation of enantiomerically enriched D-beta-heterocyclic alanine derivatives using Escherichia coli aromatic L-amino acid transaminase.
An enzymatic resolution was carried out for the preparation of enriched beta-heterocyclic D-alanine derivatives using Escherichia coli aromatic L-amino acid transaminase. The excess of pyrazole, imidazole, or 1,2,4-triazole reacted with methyl-2-acetamidoacrylate in acetonitrile in the presence of potassium carbonate at 60 degrees C, directly leading to make the potassium salt of the corresponding N-acetyl-beta-heterocyclic alanine derivatives. After the acidic deprotection of the N-acetyl group, 10 mM of racemic pyrazolylalanine, triazolylalanine, and imidazolylalanine were resolved to D-pyrazolylalanine, D-triazolylalanine, and D-imidazolylalanine with 46% (85% ee), 42% (72% ee), and 48% (95% ee) conversion yield in 18 h, respectively, using E. coli aromatic L-amino acid transaminase (EC 2.6.1.5). Although the three beta-heterocyclic L-alanine derivatives have similar molecular structures, they showed different reaction rates and enantioselectivities. The relative reactivities of the transaminase toward the beta-heterocyclic L-alanine derivatives could be explained by the relationship between the substrate binding energy (E, kcal/mol) to the enzyme active site and the distance (delta, A) from the nitrogen of alpha-amino group of the substrates to the C4' carbon of PLP-Lys258 Schiff base. As the ratio of the substrate binding energy (E) to the distance (delta) becomes indicative value of k(cat)/K(M) of the enzyme to the substrate, the relative reactivities of the beta-heterocyclic L-alanine derivatives were successfully correlated with E/delta, and the relationship was confirmed by our experiments.
Cho
Byung-Kwan
BK
School of Chemical Engineering and Institute of Molecular Biology and Genetics, Seoul National University, Seoul 151-742, Korea.
Park
Hyung-Yeon
HY
Seo
Joo-Hyun
JH
Kinnera
Koteshwar
K
Lee
Bon-Su
BS
Kim
Byung-Gee
BG
D000409:Alanine / Q000138:chemical synthesis*; D001142:Aromatic-L-Amino-Acid Decarboxylases; D001665:Binding Sites; D003198:Computer Simulation; D004789:Enzyme Activation; D004926:Escherichia coli / Q000201:enzymology*; D006571:Heterocyclic Compounds / Q000138:chemical synthesis*; D007700:Kinetics; D008956:Models, Chemical; D008958:Models, Molecular; D011485:Protein Binding; D013237:Stereoisomerism; D014444:Tyrosine Transaminase / Q000032:analysis* / Q000737:chemistry*
D006571:Heterocyclic Compounds; D014444:Tyrosine Transaminase; D001142:Aromatic-L-Amino-Acid Decarboxylases; D000409:Alanine