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ИСТИНА ЦЭМИ РАН |
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Penicillin acylase from Escherichia coli and its mutants stabilized to inactivation in alkaline medium and by high substrate concentrations have been used for preparative stereoselective synthesis of substituted and unsubstituted 2-hydroxyacyl derivatives of alpha-amino acids which then after activation of their carboxyl group by N,N’-dicyclohexylcarbodiimide were subjected to intramolecular cyclization to produce corresponding 2,5-diketomorpholines. Biocatalytic acylation in aqueous alkaline medium was very effective: for example at pH 9.5 acylation of 0.1 M DL-phenylalanine by 0.2 M (R)-mandelamide was 99% (yield calculated per amount of L-enantiomer of amino acid, synthesis/hydrolysis ratio 35). Due to the high stereoselectivity of enzyme to nucleophile (E ≈ 1000) N-(R)-mandelyl-(S)-phenylalanine (e.e. 99.9%) was produced. Using this methodology different cyclodidepsipeptides were synthesized with a good overall yield.