Stereochemical Insights into the Anaerobic Degradation of 4-Iso-propylbenzoyl-CoA in the Denitrifying Bacterium Strain pCyN1


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marvin.doerries [ at ] hifmb.de

Abstract

The constitutions and absolute configurations of two so far unknown intermediates, (1S,2S,4S)-2-hydroxy-4-isopropylcyclohexane-1-carboxylate and (S)-3-isopropylpimelate, of anaerobic degradation of p-cymene in the bacterium "Aromatoleum aromaticum" pCyN1 are reported. These intermediates (as CoA esters) are involved in the further degradation of 4-isopropylbenzoyl-CoA formed by methyl group hydroxylation and subsequent oxidation of p-cymene. Proteogenomics indicated 4-isopropylbenzoyl-CoA degradation to involve (i) a novel member of class I benzoyl-CoA reductase (BCR) as known from Thauera aromatica K172 and (ii) a modified β-oxidation pathway yielding 3-isopropylpimeloyl-CoA analogously to benzoyl-CoA degradation in Rhodopseudomonas palustris. Reference standards of all four diastereoisomers of 2-hydroxy-4-isopropylcyclohexane-1-carboxylate as well as both enantiomers of 3-isopropylpimelate were obtained by stereoselective syntheses via methyl 4-isopropyl-2-oxocyclohexane-1-carboxylate. The stereogenic center carrying the isopropyl group was established using a rhodium-catalyzed asymmetric conjugate addition. X-ray crystallography revealed that the thermodynamically most stable stereoisomer of 2-hydroxy-4-isopropylcyclohexane-1-carboxylate is formed during p-cymene degradation. Our findings imply that the reductive dearomatization of 4-isopropylbenzoyl-CoA by the BCR of "A. aromaticum" pCyN1 stereospecifically forms (S)-4-isopropyl-1,5-cyclohexadiene-1-carbonyl-CoA



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Eprint ID
48868
DOI 10.1002/chem.201805837

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Christoffers, J. , Küppers, J. , Becker, P. , Jarling, R. , Dörries, M. , Cakic, N. , Schmidtmann, M. , Rabus, R. and Wilkes, H. (2019): Stereochemical Insights into the Anaerobic Degradation of 4-Iso-propylbenzoyl-CoA in the Denitrifying Bacterium Strain pCyN1 , Chemistry . doi: 10.1002/chem.201805837


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