title: Chemoenzymatic Kinetic resolution of (R)-malathion in aqueous media.
abstract: BACKGROUND
  Malathion (R,S)-diethyl-2-[(dimethoxyphosphorothioyl)sulfanyl]butanedioate is a chiral organophosphorus compound used widely as pesticide for suppression of harmful insects such as mosquitoes. It is well known that in biological systems (R)-malathion is the active enantiomer, therefore a sustainable approach could be the use of only the biologically active enantiomer. The resolution of the commercial racemic mixture to obtain the pure active enantiomer combined with a recycling of the undesired enantiomer through a racemization process could be an attractive alternative to reduce the environmental impact of this pesticide. Thus, this work evaluates the use of four commercially available lipases for enantioselective hydrolysis and separation of malathion enantiomers from the commercial racemic mixture.
  
  
  RESULTS
  Several lipases were methodologically assessed, considering parameters such as enzyme concentration, temperature and reaction rates. Among them, Candida rugosa lipase exhibited the best performance, in terms of enantioselectivity, E = 185 (selective to the (S)-enantiomer). In this way, the desired unreacted (R)-enantiomer was recovered in a 49.42 % yield with an enantiomeric excess of 87 %. The monohydrolized (S)-enantiomer was recovered and racemized in basic media, followed by esterification to obtain the racemic malathion, which was recycled. In this way, an enantioenriched mixture of (R)-malathion was obtained with a conversion of 65.80 % considering the recycled (S)-enantiomer.
  
  
  CONCLUSIONS
  This work demonstrated the feasibility of exploiting Candida rugosa lipase to kinetically resolve racemic malathion through an environmentally friendly recycling of the undesired (S)-enantiomer. Graphical AbstractLipase catalyzed enantioselective resolution of (R)-malathion in aqueous solvent.
authors.affiliation: Facultad de Ciencias Químicas, Universidad Autónoma de Chihuahua, Circuito No.1 Campus Universitario, Chihuahua, Arboledas, Chihuahua 31125 Apartado Postal 669, , México.
authors.forename: Carlos A
authors.initials: CA
authors.lastname: Enríquez-Núñez
authors.affiliation: Facultad de Ciencias Químicas, Universidad Autónoma de Chihuahua, Circuito No.1 Campus Universitario, Chihuahua, Arboledas, Chihuahua 31125 Apartado Postal 669, , México.
authors.forename: Alejandro A
authors.initials: AA
authors.lastname: Camacho-Dávila
authors.affiliation: Facultad de Ciencias Químicas, Universidad Autónoma de Chihuahua, Circuito No.1 Campus Universitario, Chihuahua, Arboledas, Chihuahua 31125 Apartado Postal 669, , México.
authors.forename: Víctor H
authors.initials: VH
authors.lastname: Ramos-Sánchez
authors.affiliation: Facultad de Ciencias Químicas, Universidad Autónoma de Chihuahua, Circuito No.1 Campus Universitario, Chihuahua, Arboledas, Chihuahua 31125 Apartado Postal 669, , México.
authors.forename: Gerardo
authors.initials: G
authors.lastname: Zaragoza-Galán
authors.affiliation: Facultad de Ciencias Químicas, Universidad Autónoma de Chihuahua, Circuito No.1 Campus Universitario, Chihuahua, Arboledas, Chihuahua 31125 Apartado Postal 669, , México.
authors.forename: Lourdes
authors.initials: L
authors.lastname: Ballinas-Casarrubias
authors.affiliation: Facultad de Ciencias Químicas, Universidad Autónoma de Chihuahua, Circuito No.1 Campus Universitario, Chihuahua, Arboledas, Chihuahua 31125 Apartado Postal 669, , México.
authors.forename: David
authors.initials: D
authors.lastname: Chávez-Flores
keywords: Enantiomer; Enzymatic; Malathion; Resolution