Open AccessLevetiracetam analogs: chemoenzymatic synthesis, absolute configuration assignment and evaluation of cholinesterase inhibitory activities
Author(s) -
Cíntia D. F. Milagre,
Bruno S. do Amaral,
João M. Batista,
Adriana Ferreira Lopes Vilela,
Carmen L. Cardoso,
Humberto M. S. Milagre
Publication year - 2022
Publication title -
eclética química
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.177
H-Index - 19
eISSN - 1678-4618
pISSN - 0100-4670
DOI - 10.26850/1678-4618eqj.v47.2.2022.p36-73
Subject(s) - chemistry , nitrile , absolute configuration , enantiomer , enantiomeric excess , kinetic resolution , circular dichroism , stereochemistry , combinatorial chemistry , organic chemistry , enantioselective synthesis , catalysis
A chemoenzymatic approach for the synthesis of ?-N-heterocyclic ethyl- and phenylacetamides, levetiracetam analogs, is described. Eight nitrile substrates were prepared through the N-alkylation of heterocycles (2-pyrrolidinone, 2-piperidinone, 2-oxopiperazine and 1-methylpiperazine) directly from hydroxyl group of ethyl and phenyl ?-hydroxynitriles with yield of 35?71% after 12 h. Twenty nitrile hydratases (NHases) were screened and showed that the N-derivatives lactam substrates led to their correspondent amides by Co-type NHase with conversion and enantiomeric excess of up to 47.5 and 52.3% for (S)-enantiomer, while the piperazine substrates underwent spontaneous decomposition by retro-Strecker reaction. In order to avoid a retro-Strecker reaction of ?-aminonitriles, ionic liquids and polyethylene glycol (PEG400) were evaluated as alternative green solvents to aqueous buffered solutions in different proportions. Temperature was another parameter investigated during reaction-medium engineering for process optimization. However, unconventional reaction media and low temperature significantly reduced the NHase activity. The absolute configuration of ?-N-heterocyclicethyl- and phenylacetamides, some of which were new compounds, was determined using electronic circular dichroism (ECD) spectroscopy. Additionally, their potential as cholinesterases inhibitors was evaluated.