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Stereochemistry and Mechanism of Enzymatic and Non‐Enzymatic Hydrolysis of Benzylic sec ‐Sulfate Esters
Author(s) -
Toesch Michael,
Schober Markus,
Breinbauer Rolf,
Faber Kurt
Publication year - 2014
Publication title -
european journal of organic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.825
H-Index - 155
eISSN - 1099-0690
pISSN - 1434-193X
DOI - 10.1002/ejoc.201402211
Subject(s) - chemistry , enzymatic hydrolysis , enzyme , mechanism (biology) , hydrolysis , stereochemistry , sulfate , organic chemistry , enzyme catalysis , philosophy , epistemology
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 18 O‐labeled buffer by using an enantiopure sec ‐benzylic sulfate ester as substrate revealed that from the three possible pathways (i) inverting S N 2‐type nucleophilic attack of [OH – ] at the benzylic carbon represents the major pathway, whereas (ii) S N 1‐type formation of a planar benzylic carbenium ion leading to racemization was a minor event, and (iii) Retaining S N 2‐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.