Stereochemistry and Mechanism of Enzymatic and Non-Enzymatic Hydrolysis of Benzylic sec-Sulfate Esters.

ABSTRACT: The substrate scope of inverting alkylsulfatase Pisa1 was extended towards benzylic sec-sulfate esters by suppression of competing non-enzymatic autohydrolysis by addition of dimethyl sulfoxide as co-solvent. Detailed investigation of the mechanism of autohydrolysis in ¹⁸O-labeled buffer by using an enantiopure sec-benzylic sulfate ester as substrate revealed that from the three possible pathways (i) inverting S_N2-type nucleophilic attack of [OH^-] at the benzylic carbon represents the major pathway, whereas (ii) S_N1-type formation of a planar benzylic carbenium ion leading to racemization was a minor event, and (iii) Retaining S_N2-type nucleophilic attack at sulfur took place at the limits of detection. The data obtained are interpreted by analysis of Hammett constants of meta substituents.

SUBMITTER: Toesch M 

PROVIDER: S-EPMC4163651 | biostudies-literature |

REPOSITORIES: biostudies-literature