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Enzymatic separation of cis and trans isomers of alicyclic alcohols
Authors:Alexander M Klibanov  Akella Chendrasekhar  Barbara N Alberti
Institution:Laboratory of Applied Biochemistry, Department of Nutrition and Food Science, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
Abstract:It has been discovered that phosphatases alkaline phosphatase, orthophosphoric-monoester phosphohydrolase (alkaline optimum), EC 3.1.3.1, and acid phosphatase, orthophosphoric-monoester phosphohydrolase (acid optimum), EC 3.1.3.2] display a remarkable geometric specificity in the hydrolysis of cis and trans isomers of monoorthophosphate esters of substituted alicy clicalcohols. While steric hindrances prevent potato acid phosphatase from hydrolysing cis-2-methylcyclohexyl and cis-2-methylcyclopentyl phosphates, the corresponding trans isomers are readily hydrolysed by the enzyme (non-enzymatic, acid-catalysed or base-catalysed hydrolyses of the cis and trans isomers occur at similar rates). Cis isomers of methylcyclohexyl phosphates, in which the methyl group is remote from the hydrolysed ester bond, 3- or 4-, have nearly the same reactivities to phosphatases as their trans counterparts. However, if the methyl group in position 4 is replaced by a bulky substituent, e.g. tert-butyl, phosphatases again hydrolyse only the trans and not the cis isomer. These phenomena afford a simple method for preparative separation of cis and trans isomers of alicyclic alcohols: a mixture of the isomers is first phosphorylated with POCl3 and then hydrolysed by phosphatase. The trans alcohol formed is extracted with CCl4, followed by alkaline hydrolysis of the remaining cis-tester and subsequent extraction of the cis alcohol produced.
Keywords:Alcohols  isomers  phosphatase  bioseparations  enzyme specificity
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