6070-14-0Relevant articles and documents
Biocatalytic enantiomeric resolution of L-menthol from an eight isomeric menthol mixture through transesterification
Brady,Reddy,Mboniswa,Steenkamp,Rousseau,Parkinson,Chaplin,Mitra,Moutlana,Marais,Gardiner
scheme or table, p. 1 - 10 (2012/03/27)
The four diastereomers of menthol and their enantiomers, namely dl-menthol, dl-neomenthol, dl-neoisomenthol and dl-isomenthol, were synthesised by the hydrogenation of thymol to yield an eight isomer liquid menthol. A suitably selective lipase was sought to preferentially esterify l-menthol in organic solvent, hence simplifying separation from the diasteromeric mix through distillation. From an initial screen a commercial Pseudomonas fluorescens lipase (Amano AK) was selected, and vinyl acetate was chosen as a suitable irreversible acyl donor for transesterification. The reaction reagent ratios were optimised, and an enantiomeric excess (ee) of l-menthol of greater than 95% was reproducibly achievable at a conversion of 30% dl-menthol (0.68 M) at ≤50°C. On the basis of the composition of liquid menthol the reaction had a diastereomeric excess (de) of 82%. The enzyme was recycled 150 times in 5 ml batch reactions using liquid menthol and achieving an overall yield of 184.3 g dl-menthol/g commercial enzyme preparation. The by-product acetic acid, formed by hydrolysis of menthyl acetate, was found to cause a high degree of enzyme inactivation. The resolution reaction was scaled up 400 fold to 2 L and the enzyme recycled 38 times with an average conversion of the available l-menthol of 59% and a volumetric productivity of 1.2 g/L/h.
Candida Rugosa lipase: Enantioselectivity enhancements in organic solvents
Persichetti, Rose A.,Lalonde, Jim J.,Govardhan, Chandrika P.,Khalaf, Nazer K.,Margolin, Alexey L.
, p. 6507 - 6510 (2007/10/03)
Chiral resolutions of carboxylic acids (1-3) and alcohol (4) were carried out through esterification or transesterification in organic solvents using cross-linked enzyme crystals (CLEC) of Candida rugosa lipase (CRL). Comparison of these results with those of crude CRL reveal significant differences. As was seen in resolution through hydrolysis, a marked improvement in enantioselectivity is realized with the CLEC. Additionally, the stability afforded the enzyme in CLEC form leads to a higher activity in organic solvent.
