title: Stereochemistry and Mechanism of Enzymatic and Non-Enzymatic Hydrolysis of Benzylicsec-Sulfate Esters.
abstract: The substrate scope of inverting alkylsulfatase Pisa1 was extended towards benzylicsec-sulfate esters by suppression of competing non-enzymatic autohydrolysis by addition of dimethyl sulfoxide as co-solvent. Detailed investigation of the mechanism of autohydrolysis in18O-labeled buffer by using an enantiopuresec-benzylic sulfate ester as substrate revealed that from the three possible pathways (i) inverting SN2-type nucleophilic attack of [OH-] at the benzylic carbon represents the major pathway, whereas (ii) SN1-type formation of a planar benzylic carbenium ion leading to racemization was a minor event, and (iii) Retaining SN2-type nucleophilic attack at sulfur took place at the limits of detection. The data obtained are interpreted by analysis of Hammett constants ofmetasubstituents.
authors.affiliation: Department of Chemistry, Organic & Bioorganic Chemistry, University of Graz, Heinrichstrasse 28, 8010 Graz, Austria.
authors.forename: Michael
authors.initials: M
authors.lastname: Toesch
authors.affiliation: Department of Chemistry, Organic & Bioorganic Chemistry, University of Graz, Heinrichstrasse 28, 8010 Graz, Austria.
authors.forename: Markus
authors.initials: M
authors.lastname: Schober
authors.affiliation: Department of Organic Chemistry, Graz University of Technology, Stremayrgasse 9, 8010 Graz, Austria.
authors.forename: Rolf
authors.initials: R
authors.lastname: Breinbauer
authors.affiliation: Department of Chemistry, Organic & Bioorganic Chemistry, University of Graz, Heinrichstrasse 28, 8010 Graz, Austria.
authors.forename: Kurt
authors.initials: K
authors.lastname: Faber
keywords: Configuration determination; Enzyme catalysis; Hammett constant; Hydrolysis; Reaction mechanisms; Synthetic methods