Enhancing the enantioselectivity of the lipase from Burkholderia cepacia LTEB11 towards the resolution of secondary allylic alcohols

Burkholderia cepacia LTBE11 lipase was used in the kinetic resolution of four secondary allylic alcohols by transesterification reactions with vinyl acetate: rac-1 [1-phenylprop-2-en-1-ol], rac-2 [1-(4-chlorophenyl)prop-2-en-1-ol], rac-3 [1-(3-methoxyphenyl)prop-2-en-1-ol] and rac-4 [5-methylhex-1-en-3-ol]. Greater enantioselectivities, expressed as the enantiomeric ratio (ERS or ESR, as appropriate), were obtained with the addition of the lipase immobilized on a polypropylene support (Accurel) than with the addition of a powdered free enzyme preparation. The fast-reacting enantiomer was the R-enantiomer for the alcohols with aromatic substituents (rac-1, rac-2 and rac-3) and the S-enantiomer for the alcohol with an aliphatic substituent (rac-4). The ERS values obtained for rac-1, rac-2 and rac-3 were greater than the ESR value obtained for rac-4. With the increasing temperature, ERS decreased for rac-2 and rac-3, while ESR increased for rac-4. Thermodynamic analysis of the difference in activation energies based on the temperature data showed that ΔR−SΔH# and ΔR−SΔS# were negative in all cases. For rac-2 and rac-3, the selectivity for the R-enantiomer was due to a predominance of enthalpic effects (i.e. ∣ΔR−SΔH#∣>∣TΔR−SΔS#∣). For rac-4, the selectivity for the S-enantiomer was due to a predominance of entropic effects (i.e. ∣TΔR−SΔS#∣>∣ΔR−SΔH#∣). The resolution of rac-2 was investigated in different solvents. ERS enhanced with the increasing values of log P and molecular volume of the solvent but decreased with the increasing dielectric constant. The highest ERS value, 110, was obtained in n-heptane. This elevated enantioselectivity suggests that the lipase of B. cepacia LTBE11 has good potential for the application in the resolution of secondary allylic alcohols.