Resolution Of 2-octanol By Lipases In Ionic Liquid

Chiral is a universal phenomenon in the natural world.Organisms constitute the basic material,such as amino acids,proteins,nucleic acids,carbohydrates and other biological molecules are chiral molecules.Apart from a few exceptions,almost all amino acids are L-type,polysaccharides and nucleic acid in sugar is D-type.Many drugs,physical substances,pesticides and herbicides are also optically active compounds.When the optical compound goes into the body,its pharmacological and physiological role relate with the match of target molecule between molecular recognition and ability.Enantiomerically pure alcohols and their derivatives are important synthetic intermediates,which have been widely used in many fields such as liquid crystals,medicaments,agricultural chemicals and organic non-linear materials.Kinetic resolution catalyzed by lipases show high enantioselectivity.In addition,there are many merits in lipases-catalyzed reaction of organic synthesis, such as their much milder reaction conditions,friendly environments,quick rate and high selectivity.Although nonaqueous enzymatic reaction workup easily,the conventional organic reaction media restrict enzyme activity and stability.Over the past decade,many groups attempted to resolve the problems of enzyme immobility and deactivation in organic solvent.Recently many groups was interested in application of room temperature ionic liquid as novel solvents replace of conventional organic reaction media in enzyme-catalyzed reaction.Room temperature ionic liquids consist of an organic cation and inorganic anion, the ions do not pack well and remain liquid at room temperature.They are low-melting(＜100℃),and the properties of ionic liquids largely depend on the cation and anion.Different kind of enzyme,especially lipase that tolerate organic solvent well,have unusual exhibition in ionic liquid,whose activity is generally comparable with,or better than those observed in organic reaction media.In addition, because of their particular molecule frame the ionic liquid acts as a reservoir for enzyme suspended in them,which could reduce the enzyme deactivation and advance enantioseletivity.At present,[RMIM]⁺[PF₆]^-and[RMIM]⁺[BF₄]^-were chosen reaction media of enzymatic reaction in ionic liquid since enzyme's activity and stability were improved in them.The resolution of 2-octanol in ionic liquids was investigated using Pseudomonas S.P.Lipase(PSL) as biocatalyst.In the meantime, some methods that can increase selectivity of lipase in ionic liquids were also explored.The optimum resolution conditions were as followings:acyl doner:vinyl acetate,reaction medium:[C₆MIM][BF₄],temperature:40℃,PH:7.0,a_w:0.28, content of PSL:10 mg,substrate ratio(2-octanol:vinyl acetate):1:2.As an environmentally benign method,the applications of ultrasound in organic chemistry have developed rapidly in recent years.Because the mechanical effect of the acoustic waves could enhance the velocity of heterogeneous reactions,ultrasound is also a useful tool in nonaqueous enzymology.Although study on ultrasound-promoted lipase-catalyzed reaction was reported in the world in recent years.However,experts have different ideas.Based on the resolution of 2-octanol in ionic liquids,this paper studied the effect of ultrasound on the lipase-catalyzed reaction and the possible mechanism of ultrasound have also been discussed.Our result shows that ultrasound can play an important role in lipase-catalyzed reaction. Low energy ultrasound can increases the reaction rate.However,high energy ultrasound is not beneficial to the reaction.The best of methods of ultrasound is the interval ultrasound.The effect of temperature is also obvious under the ultrasound, because the molecules shake more drastically.In addition,the use of time under ultrasound can also change the optimum temperature.The optimum resolution conditions:20 KHz,temperature:30℃,with the power of 80 Watt irratiating 30 seconds,followed by an interval of 60 seconds.