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Ecl�tica Qu�mica Journal, 2(47), p. 36-73, 2022

DOI: 10.26850/1678-4618eqj.v47.2.2022.p36-73

Ecl�tica Qu�mica Journal, 2(47), p. 17-35, 2022

DOI: 10.26850/1678-4618eqj.v47.2.2022.p17-35

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Levetiracetam analogs: chemoenzymatic synthesis, absolute configuration assignment and evaluation of cholinesterase inhibitory activities

This paper is made freely available by the publisher.
This paper is made freely available by the publisher.

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Abstract

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-heterocyclic�ethyl- and phenylacetamides, some of which were new compounds, was determined using electronic circular dichroism (ECD) spectroscopy. Additionally, their potential as cholinesterase�s inhibitors was evaluated.