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Stereochemistry and Fate of Hydrogen Atoms in the Diol‐Dehydratase‐Catalyzed Dehydration of meso ‐Butane‐2,3‐diol
Author(s) -
Manitto Paolo,
Speranza Giovanna,
Fontana Gabriele,
Galli Antonietta
Publication year - 1998
Publication title -
helvetica chimica acta
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.74
H-Index - 82
eISSN - 1522-2675
pISSN - 0018-019X
DOI - 10.1002/(sici)1522-2675(19981111)81:11<2005::aid-hlca2005>3.0.co;2-2
Subject(s) - chemistry , butane , diol , hydrogen atom , stereochemistry , catalysis , dehydration reaction , methyl group , dehydratase , alcohol , medicinal chemistry , organic chemistry , enzyme , group (periodic table)
The transformation of meso ‐butane‐2,3‐diol into butan‐2‐ol by a strain of Lactobacillus brevis occurs through a diol‐dehydratase‐catalyzed conversion of the diol into butan‐2‐one, which is then reduced to the secondary alcohol by dehydrogenases. Experiments performed with deuterated meso ‐butane‐2,3‐diols showed that the dehydration reaction brings about an inversion of configuration at the ( R )‐configured C‐atom of meso ‐butane‐2,3‐diol as a consequence of the substitution of the OH group by a H‐atom; at the same time, the H‐atom already bound to the ( R ) C‐atom is retained in the resulting methylene group. The H‐atom replacing the OH group was assessed to come from the medium since the H‐atom at the ( S )‐configured C‐atom was completely lost. By contrast, in the case of the conversion of ( RS )‐propane‐1,2‐diol into propan‐1‐ol under the same fermentation conditions, an extensive H‐transfer ( ca . 80%) from the primary‐alcohol function to the adjacent C‐atom was observed. This fact is taken as an indication of different modes in which the two substrates are processed by the enzyme (despite the same stereochemical outcome). A speculative hypothesis is presented to interpret such a dissimilarity.