Inverting the Regioselectivity of the Berberine Bridge Enzyme by Employing Customized Fluorine‐Containing Substrates

Verena Resch,Horst Lechner,Karl Gruber,Silvia Wallner,Wolfgang Kroutil,Peter Macheroux,Joerg H Schrittwieser

doi:10.1002/chem.201201895

Verena Resch, Horst Lechner + Show 5 more

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https://doi.org/10.1002/chem.201201895

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Journal: Chemistry	Publication Date: Sep 7, 2012
Citations: 29	License type: unspecified-oa

Affiliation: University of Graz, Graz University of Technology

Abstract

Fluorine is commonly applied in pharmaceuticals to block the degradation of bioactive compounds at a specific site of the molecule. Blocking of the reaction center of the enzyme-catalyzed ring closure of 1,2,3,4-tetrahydrobenzylisoquinolines by a fluoro moiety allowed redirecting the berberine bridge enzyme (BBE)-catalyzed transformation of these compounds to give the formation of an alternative regioisomeric product namely 11-hydroxy-functionalized tetrahydroprotoberberines instead of the commonly formed 9-hydroxy-functionalized products. Alternative strategies to change the regioselectivity of the enzyme, such as protein engineering, were not applicable in this special case due to missing substrate–enzyme interactions. Medium engineering, as another possible strategy, had clear influence on the regioselectivity of the reaction pathway, but did not lead to perfect selectivity. Thus, only substrate tuning by introducing a fluoro moiety at one potential reactive carbon center switched the reaction to the formation of exclusively one regioisomer with perfect enantioselectivity.

Highlights

Enzymes are regio- and enantioselective catalysts, which makes them more frequently applied complementary tools in organic synthesis.[1,2]. Their excellent selective nature is sometimes considered as a limitation to their substrate and reaction spectrum
To promote the formation of 11-hydroxy-functionalized tetrahydroprotoberberines instead of the commonly formed 9hydroxy-functionalized products from 1,2,3,4-tetrahydroisoquinolines catalyzed by berberine bridge enzyme (BBE), a customized substrate strategy was successfully applied
Introducing fluoro substituents is a common strategy to avoid the degradation of pharmaceuticals.[17]

Summary

Introduction

Enzymes are regio- and enantioselective catalysts, which makes them more frequently applied complementary tools in organic synthesis.[1,2] their excellent selective nature is sometimes considered as a limitation to their substrate and reaction spectrum. The wild-type enzyme BBE transformed the racemic substrate rac-1 b to a 91:9 mixture of the regioisomers 2 b/3 b in toluene/buffer 70:30 (pH 9).

Results

Conclusion