Oxygen-Free Regioselective Biocatalytic Demethylation of Methyl-phenyl Ethers via Methyltransfer Employing Veratrol-O-demethylase

Abstract

The cleavage of aryl methyl ethers is a common reaction in chemistry requiring rather harsh conditions; consequently, it is prone to undesired reactions and lacks regioselectivity. Nevertheless, O -demethylation of aryl methyl ethers is a tool to valorize natural and pharmaceutical compounds by deprotecting reactive hydroxyl moieties. Various oxidative enzymes are known to catalyze this reaction at the expense of molecular oxygen, which may lead in the case of phenols/catechols to undesired side reactions (e.g., oxidation, polymerization). Here an oxygen-independent demethylation via methyl transfer is presented employing a cobalamin-dependent veratrol- O -demethylase (vdmB). The biocatalytic demethylation transforms a variety of aryl methyl ethers with two functional methoxy moieties either in 1,2-position or in 1,3-position. Biocatalytic reactions enabled, for instance, the regioselective monodemethylation of substituted 3,4-dimethoxy phenol as well as the monodemethylation of 1,3,5-trimethoxybenzene. The methyltransferase vdmB was also successfully applied for the regioselective demethylation of natural compounds such as papaverine and rac -yatein. The approach presented here represents an alternative to chemical and enzymatic demethylation concepts and allows performing regioselective demethylation in the absence of oxygen under mild conditions, representing a valuable extension of the synthetic repertoire to modify pharmaceuticals and diversify natural products.

First and Second Sphere Interactions Accelerate Non-Native N-Alkylation Catalysis by the Thermostable, Methanol-Tolerant B12-Dependent Enzyme MtaC

“…This finding shows how first and second sphere interactions in a protein scaffold can play a significant role in directing the utility of different proteins for non-native catalysis. Combined with our previous report of non-native styrene alkylation using CarH* 14 and studies exploring the substrate scope of B12-depenent methyl transferases, 22,23 this study highlights the utility of corrinoid proteins for biocatalysis and how structure-based homology searches can be used to identify enzymes for this purpose.…”

Controlling Non-Native B12 Reactivity and Catalysis in the Transcription Factor CarH

“…B12-dependent enzymes are underutilized in biocatalysis relative to other metalloenzymes. Recent examples exploring the substrate scope of native B12-dependent enzyme catalysis 4,34 and the broad range of reactions catalyzed by B12 cofactors 7 suggest that suitable systems could find broader application in biocatalysis. This study establishes that a B12-dependent enzyme can catalyze a transformation distinct from its native reaction.…”

Thiols Act as Methyl Traps in the Biocatalytic Demethylation of Guaiacol Derivatives

“…The one pot protocol was shown to be applicable for a broad scope of substituted guaiacol derivatives, whereby many of them were transformed with a conversion exceeding 90 %, at 30 °C and mild pH (pH 6.5) in buffer. Furthermore, the approach should be extendable to other cobalamin dependent methyltransferases possessing different preference for the substrate pattern [27] . We envisage that the substrate scope could be broadened by enzyme engineering.…”