C-chiral alkyl sulfates 11, which are sulfate esters of secondary alcohols, are hydrolytically cleaved by the enzymes sulfatases.30 Interestingly, there are two types of sulfatases - the one which cleaves the S-O bond31 and the second which cleaves the C-O bond.32 The former does not alter the configuration at the stereogenic carbon atom (Equation 9), acting in the stereochemical sense like lipases, esterases and proteases; the latter causes inversion of configuration at the carbon chirality centre (Equation 10). In the first case, a normal kinetic resolution of the racemic sulfate can be performed to give unreacted sulfate 11 and the alcohol 12, both having opposite absolute configurations at the stereogenic carbon atom. In the second case, starting from the racemic substrate a mixture of the unreacted substrate 11 and the alcohol 12 is obtained, each of them having the same absolute configuration. Such a result makes it possible to use this type of sulfatase in a deracemization process, in which a racemic substrate is converted into a single enantiomer of a product. This approach was used by Faber and coworkers32 for deracemization of secondary alcohols. It should be added that the final transformation of 11 into 12 was stereospecifically performed by hydrolysis using p-toluenesulfonic acid in aqueous t-butyl methyl ether-dioxane.32e
Arylsulfatase from Pseudomonas aeruginosa3'13 Sulfatase from Rhodopimllula baltica31b
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