Asymmetric chemoenzymatic synthesis of N-acetyl-α-amino esters based on lipase-catalyzed kinetic resolutions through interesterification reactions |
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Authors: | Marcos Reinaldo da Silva Marcos Carlos de Mattos Maria da Conceição Ferreira de Oliveira Telma Leda Gomes de Lemos Nágila Maria Pontes Silva Ricardo Gonzalo de Gonzalo Iván Lavandera Vicente Gotor-Fernández Vicente Gotor |
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Institution: | 1. Departamento de Química Orgânica e Inorgânica, Universidade Federal do Ceará, 60451-970 Fortaleza, Ceará, Brazil;2. Departamento de Química Orgánica e Inorgánica, Instituto Universitario de Biotecnología de Asturias, Universidad de Oviedo, c/Julián Clavería 8, 33006 Oviedo, Spain |
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Abstract: | Several phenylalanine analogs have been synthesized through a four-step route starting from easily available ethyl acetamidocyanoacetate. In a first reaction, and making use of phase transfer catalysts, this compound reacted with several alkyl halides, being benzyltributylammonium chloride identified as the best one for the production of a series of quaternary amino acids in moderate to excellent yields (52–95%). Then, the corresponding N-acetyl-phenylalanine methyl and allyl ester derivatives were obtained through acidic hydrolysis, esterification, and N-acetylation. Rhizomucor miehei lipase was found as a versatile enzyme for the resolution of these amino esters, finding the best results through interesterification reactions with butyl butyrate in acetonitrile. A great influence in the stereoselectivity was found depending on the chemical structure of the compound, achieving for the non- or para-substituted in the phenyl ring excellent stereoselectivities, being moderate for the meta-nitro derivative, while the ortho-nitro amino ester did not react. |
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Keywords: | Amino acids Asymmetric synthesis Interesterification Kinetic resolution Lipases |
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