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

Article abstract of DOI:10.1021/acscatal.0c02790

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.

Full text of DOI:10.1021/acscatal.0c02790

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Research Article
Oxygen-Free Regioselective Biocatalytic Demethylation of Methyl-
phenyl Ethers via Methyltransfer Employing
Veratrol‑O‑demethylase
Christopher Grimm, Mattia Lazzarotto, Simona Pompei, Johanna Schichler, Nina Richter,
Judith E. Farnberger, Michael Fuchs, and Wolfgang Kroutil*
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*
sı Supporting Information
ABSTRACT: The cleavage of aryl methyl ethers is a common
reaction in chemistry requiring rather harsh conditions; con-
sequently, 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-demethy-
lase (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
,4-dimethoxy phenol as well as the monodemethylation of 1,3,5-trimethoxybenzene. The methyltransferase vdmB was also
3
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.
KEYWORDS: biocatalysis, biotransformation, ether cleavage, demethylation, methyltransferases, veratrol-O-demethylase
INTRODUCTION
aromatic ring or the spontaneous formation of polymerized
■
28
1
products. An alternative option avoiding molecular oxygen
involves the use of cobalamin-dependent methyltransferases
The demethylation of aryl methyl ethers is a common
transformation in organic chemistry to demask the phenol
2
9−31
2
−8
(MTases)
or O-demethylases originating from anaerobic
functionality.
Several phenolic compounds represent
32,33
3
,9
bacteria which utilize aryl methyl ethers as carbon source.
valuable pharmaceutical and natural products. In general,
chemical methods for ether cleavage require harsh reagents
A specific methyltransferase dhaf4610 from Desulfitobacterium
hafniense (D. hafniense) has been recently employed for the
methylation of catechols and demethylation of guaiacol
3
,4
such as strong acids and bases but may also be performed
5
,6
7,8
with metal catalysts and sodium thiolates. Nevertheless,
alternative approaches toward milder and selective demethy-
3
4−36
derivatives.
methionine (SAM)-dependent methyltransferases,
are restricted toward methylation only, this MTase
been shown to enable both methylation and demethylation in a
Unlike the well-investigated S-adenosyl
37−39
1
0,11
9,4w0hich
lation are demanded.
O-Demethylation of methyl aryl
2
11−14
has
ethers may also be achieved using biocatalysts:
For
such as di- and monoox-
1
5−18
example, oxidative enzymes
34,35
1
9−24
25−27
reversible manner.
Thereby, the MTase transfers the
ygenases
and fungal peroxygenases
catalyze the O-
demethylation by using molecular oxygen or hydrogen
peroxide as reagents. These enzymes are known for the
detoxification of organic compounds, degradation of lignin,
Received: June 25, 2020
Revised: August 17, 2020
25
21
and the biosynthesis of secondary metabolites. However, for
applications, the oxidative O-demethylation of protected
phenols at the expense of molecular oxygen may lead to
unwanted side products, for example, via hydroxylation at the
©
XXXX American Chemical Society
https://dx.doi.org/10.1021/acscatal.0c02790
1
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Research Article
methyl group from the cofactor methylcobalamin (Me-
In a next step, various pairs of methyl donors and acceptors
were analyzed to get a first idea of the substrate scope.
Thereby, the 1,3-phenyldiol orcinol 4n unexpectedly stood out
as methyl acceptor (Scheme 1, for not accepted methyl donors
see Supporting Information, Figure S7). This was a surprise
since the substitution pattern is not related to veratrol or its
demethylated product guaiacol 2a. Orcinol 4n was methylated
to 3-methoxy-5-methylphenol 2n. Furthermore, 3,4-dimethox-
ytoluene 1b differing to veratrol 1a by one methyl group, was
demethylated with better conversion compared to veratrol
(Scheme 1).
III 41−44
Cob )
to the substrate giving cobalt in the oxidation
I
state I (Cob ). Methylcobalamin was then regenerated by the
same MTase using a methyl donor like guaiacol 2a as
cosubstrate. Thus, for an overall methyl transfer reaction, a
methyl donor and a methyl acceptor are required. By using an
excess of one compound, the reaction may be shifted toward
demethylation or methylation. It is worthwhile to note that the
cobalamin is bound to a carrier protein, the corrinoid protein
(
CP), which was in the case above the corrinoid protein
dhaf4611 originating from the same organism.
Unfortunately, the MTase from D. hafniense is limited to
guaiacol derivatives as substrates for demethylation (i.e.,
methyl donor) and catechol derivatives as methyl acceptor.
Thus, in a typical reaction, the methyl transfer occurred from
the substrate guaiacol 2a as methyl donor to 3,4-dihydrox-
The methyltransfer reaction employing MT-vdmB/
dhaf4611 was optimized regarding the type of buffer salt,
2
+
pH, the concentration of Zn , temperature, cosolvents, and
the ratio between MT-vdmB and the carrier protein dhaf4611.
Best conversions were obtained at pH 6.5 in 50 mM HEPES,
MES, or MOPS buffer (Supporting Information, Figure S1).
Nevertheless, the biocatalyst also tolerated basic conditions in
CHES buffer (pH 9.5 and 10, Supporting Information, Figure
31,34,35
ybenzoic acid 4c as methyl acceptor.
Since many natural and pharmaceutical compounds
45,46
contain more than one protected methoxy group in close
proximity and due to the limitation of the substrate pattern of
the MTase from D. hafniense, alternative enzymes transforming
substrates with fewer restrictions are needed.
47
2+
S2). According to literature, the MT-vdmB is probably Zn
dependent due to a unique zinc-binding motif D-X -C-X -C.
2
7
39
Indeed, the highest conversion was obtained in the presence of
0 μM of ZnCl , which was about twice as much as in the
2
2
RESULTS AND DISCUSSION
2+
2+
■
absence of Zn ; higher concentrations (≥50 μM Zn ) led to
less conversion (Supporting Information, Figure S3). Fur-
thermore, the optimal temperature was found to be 35 °C
(Supporting Information, Figure S4).
As a starting point, we chose the methyltransferase veratrol-O-
32,47−49
demethylase (MT-vdmB)
and the carrier protein vdmA
both originating from the same organism, namely the
50,51
anaerobic bacterium Acetobacterium dehalogenans.
The
To improve the bioavailability of less water-soluble
substrates in buffer, DMSO was investigated as cosolvent at
different concentrations (0−10%). Interestingly, best con-
versions were obtained without addition of cosolvent (18%
conv.) when using substrate 1b (10 mM) and methyl acceptor
4n (20 mM); although solubility is not an issue for these
compounds at the concentration used, 2% v/v DMSO was
chosen as suitable value for the investigation of less soluble
substrates (17% conv., Supporting Information, Figure S5). In
comparison to other cosolvents such as MeOH, EtOH, 1,4-
dioxane and THF, DMSO performed the best (Supporting
Information, Figure S6). Finally, the optimal ratio of the
methyltransferase and the carrier protein was investigated.
Applying a 1:20 ratio of the MT-vdmB/carrier protein led to
highest conversion (30% conv., Supporting Information, Table
S1).
methyltransferase MT-vdmB is described to demethylate
veratrol 1a to guaiacol 2a (Scheme 1); thus, here two methoxy
Scheme 1. Biocatalytic Demethylation of the Model
Substrates 1a and 1b
Subsequently, the optimized conditions were applied for the
demethylation of veratrol 1a and a range of 1,2-dimethoxy
substituted substrates 1b-f using a 2-fold molar excess of
orcinol 4n as methyl acceptor. At these conditions, veratrol 1a
was preferentially monodemethylated to guaiacol 2a (54%
conv.), giving at this stage of the reaction a tiny amount of the
didemethylated product catechol 4a (1%, Table 1, entry 1).
Veratrol derivatives were efficiently demethylated with up to
77% conversion as observed for the 4-methyl substituted
substrate 1b (Table 1, entries 2−6).
For selected substrates mono- as well as didemethylation
was observed, like for 1a-c and 1f. On the other hand, for
substrates 1d and 1e exclusively monodemethylated products
were observed at the analyzed stage of conversion; to perform
exclusively monodemethylation is challenging if not impossible
by chemically means. Especially 3,4-dimethoxyphenol 1d is
worthwhile to mention, since the monodemethylation
occurred with perfect regioselectivity, namely in meta-position
to the phenolic OH of the substrate 1d leading exclusively to
4-methoxyresorcinol 3d with >99% regioselectivity. So far,
groups are present in 1,2-position. This type of substrate was
not accepted by the previously described MTase from D.
3
1,34−36
hafniense.
However, when MT-vdmB was used in
combination with the carrier protein vdmA from the same
organism as described in literature, only very low conversion
for demethylation of veratrol 1a (10 mM substrate
concentration) was observed (3%) when using a 5-fold
molar excess of 3,4-dihydroxybenzaldehyde 4c as a methyl
acceptor (Scheme 1). The acceptor was converted to the
regioisomers vanillin 2c and isovanillin 3c in a 3:1 ratio. Since
optimization studies did not improve the conversion, an
alternative carrier protein was considered. Aligning carrier
proteins from other hosts with vdmA, the carrier protein
dhaf4611 from Desulfitobacterium hafniense showed the highest
sequence identity with 72% (EMBOSS needle). Remarkably,
testing now the combination of MT-vdmB with dhaf4611 led
to a higher conversion of veratrol 1a (10% conv.) compared
with the reaction with the “natural” carrier protein vdmA from
the same organism (3% conv.).
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Research Article
Table 1. Biodemethylation of Substituted Veratrol
a
Derivatives
Figure 1. Time course of the mono- and didemethylation of 3,4-
dimethoxytoluene 1b. Reaction conditions: substrate 1b (10 mM, 1.5
mg/mL), methyl acceptor 4n (20 mM, 2.5 mg/mL), vdmB (40 mg/
mL cell-free extract, ≡ 0.077 mM vdmB), CP (31 mg/mL or 1.5 mM
pure CP loaded with methyl cobalamin) in HEPES buffer (50 mM,
a
Reaction conditions: substrate 1a-f (10 mM), methyl acceptor 4n
(
20 mM, 2.5 mg/mL), vdmB (40 mg/mL cell-free extract, ≡ 0.077
pH6.5, 150 mM KCl, 20 μM ZnCl ) at 35 °C, 800 rpm in Eppendorf
2
mM vdmB), CP (31 mg/mL or 1.5 mM pure CP loaded with methyl
Thermomixer (1.5 mL) for 24 h. Total volume 120 μL. The
cobalamin) in HEPES buffer (50 mM, pH 6.5, 150 mM KCl, 20 μM
conversions were analyzed on HPLC-UV using calibration curves.
ZnCl ) at either 25 or 35 °C, 800 rpm in Eppendorf Thermomixer
2
(1.5 mL), 24 h. Total volume 500 μL. The conversions were analyzed
Since all methyl donor substrates investigated so far
contained the 1,2-dimethoxy motif, the spectrum was extended
to the 1,2,3-trimethoxy compound 1g (Table 2, entry 1). This
on HPLC-UV using calibration curves.
compound 3d was until now chemically accessible either via
(
a multistep synthesis, and (iii) by the oxidation of 5-hydroxy-
52
i) the oxidation of isovanillin 3c by the Dakin reaction, (ii)
Table 2. Product Formation of 1,3-Dimethoxybenzene
53
a
Derivatives
2
+
2
-methoxyphenyl acetate using a Cu -ascorbic acid O
2
54
system. It was also obtained by hydroxylation of guaiacol
a with a toluene 4-monooxygenase with 87% conv. at 1 mM
2
5
5
substrate concentration. The here presented enzymatic
reaction opens an alternative one-step procedure to convert
a commercially available substrate to a more valuable product.
To analyze the regioselectivity of the demethylation in more
detail, the transformation of 1b was followed over time (Figure
1
). Initially, the monodemethylated regioisomer in para-
position to the methyl group 2b (green squares) was formed
about 1.6 times faster than the corresponding regioisomer 3b
(
blue dots). After 6 h, the didemethylated product 4b started
to be formed reaching 23% after 20 h (purple triangles). From
the graph it can also be concluded that the second
demethylation step to give 4b occurs from both possible
precursors 2b and 3b, whereby it seems that 2b is preferred, as
the difference between 2b and 3b gets smaller over time. Thus,
the monodemethylation of 1b gives compound 2b with a slight
preference, which is also the preferred substrate for the second
demethylation step. A similar regioselectivity as for 1b was
observed for the benzaldehyde derivative 1c (81% para 2c,
Table 1).
a
Reaction conditions: substrate 1g-i (10 mM), methyl acceptor 4n
(20 mM, 2.5 mg/mL), vdmB (40 mg/mL cell-free extract, ≡ 0.077
mM vdmB), CP (31 mg/mL or 1.5 mM pure CP loaded with methyl
cobalamin) in HEPES buffer (50 mM, pH 6.5, 150 mM KCl, 20 μM
ZnCl ) at either 25 or 35 °C, 800 rpm in Eppendorf Thermomixer
2
(
1.5 mL) for 24 h. Total volume 500 μL. The conversions were
analyzed on HPLC-UV using calibration curves.
The temperature did not have a significant influence on the
regioselectivity when comparing biotransformations at 25 and
3
5 °C (Supporting Information, Table S2 and S3); thus, the
preference remained comparable. Nevertheless, the temper-
ature effected the amount of product formation leading in most
cases to higher conversion at higher temperature and, if a
second demethylation occurred, a higher amount of the
didemethylated product (4b, 4c, and 4g, see Supporting
Information, Table S2 and S3). The only exception was
observed in the case of the formation of 4f which was highest
at 25 °C (Supporting Information, Table S2).
motif was demethylated about 2 times faster at position 1
compared with position 2, which corresponds to the
statistically expected value. Nevertheless, after 24 h, the
didemethylated product 4g was the main compound formed
under these conditions. Since in this experiment a phenol was
formed bearing two methoxy groups in ortho-position
(compound 3g), it was investigated whether 3g is demethy-
lated as well to give 4g. Indeed, the experiment showed that
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6
0
demethylation of 3g leads exclusively to compound 4g (Entry
product is rac-yatein 1k, which is an antimicrobial and
61
2
), thus leaving one single methoxy group intact.
In a next step to extend the substrate scope even further,
antiproliferative compound against cancer cells possessing
three methoxy groups (Scheme 2 B). Interestingly, rac-yatein
1k was demethylated regioselectively at position 2 of the 1,2,3-
trimethoxy motif leading to rac-4-demethylyatein 2k. This is
actually in contrast with the observed regioselectivity in the
case of 1,2,3-trimethoxybenzene 1g, which was preferentially
demethylated at position 1. The demethylated product 2k is
found in T. occidentalis and may act as a precursor of
etoposide and teniposide, which are chemotherapeutical
agents and part of the WHO’s list of essential medicines.
compounds were investigated bearing a 1,3-dimethoxy motif
instead of the 1,2-dimethoxy motif. Surprisingly, even this type
of pattern was accepted as shown for 1,3,5-trimethoxybenzene
1
h (Entry 3). The latter was exclusively monodemethylated to
give compound 2h as a single product. Introducing an
additional methyl group as in substrate 1i, showed that again
exclusively monodemethylation occurred, whereby the two
regioisomers 2i/3i were formed in a ratio of ∼2:1
corresponding to the statistical value.
62
63
64
As the 1,2-dimethoxy as well as the 1,2,3-trimethoxy are
regular motifs found in a plethora of natural products, we
turned our attention in a next step to these more complex
molecules. The regioselective demethylation of natural
products may enable diversification to access other or even
new derivatives in a selective manner and may be a tool to
valorize natural and pharmaceutical compounds by deprotect-
ing reactive hydroxyl moieties. Since the demethylation is
performed in the absence of molecular oxygen, oxidation-
sensitive functionalities present in the substrates and/or
products will be preserved. The first natural substrate
investigated was papaverine 1j which is produced by the
CONCLUSIONS
■
The cobalamin-dependent methyltransferase MT-vdmB (vera-
trol-O-demethylase from A. dehalogenans) in combination with
the cobalamin carrier protein dhaf4611 from D. hafniense
demethylated 1,2- and 1,3-dimethoxy as well as 1,2,3-
trimethoxy derivatives under inert atmosphere via methyl
transfer. The MT-vdmB accepts a wide range of aromatic
substrates with two methoxy moieties either in close proximity
to each other (1,2-position) such as in 3,4-dimethoxytoluene
1
b or in 1,3-position such as in 2,6-dimethoxyphenol 3g. The
MT-vdmB showed clear regioselectivity for the demethylation
of the methoxy moiety located in the para-position to the
substituent like in 3,4-dimethoxytoluene 1b and 3,4-dimethox-
ybenzaldehyde 1c. For other substrates, like 3,4-dimethox-
yphenol 1d, perfect regioselectivity was observed leading
exclusively to 4-methoxyresorcinol 3d with >99% regioselec-
tivity. Natural products such as papaverine 1j and rac-yatein 1k
were demethylated in a regioselective fashion. The demethy-
lation of these natural compounds indicates that the
biocatalytic methyltransfer approach paves the way to
alternative, environmentally benign, oxygen-free demethylation
methods to possible novel bioactive agents/pharmaceuticals.
56
opium plant Papaver somniferum. Papaverine 1j contains
twice the 1,2-dimethoxybenzene motif, thus in total four
methoxy groups (Scheme 2A). Papaverine 1j was preferentially
Scheme 2. Biotransformation of Pharmaceutical Relevant
Compounds (A) Papaverine and (B) Rac-yatein
ASSOCIATED CONTENT
sı Supporting Information
The Supporting Information is available free of charge at
https://pubs.acs.org/doi/10.1021/acscatal.0c02790.
■
*
Results of the optimization study, experimental
procedures for enzyme expression and purification, set
up of biotransformations, and analytical methods (PDF)
AUTHOR INFORMATION
Corresponding Author
■
Wolfgang Kroutil − Institute of Chemistry, University of Graz,
NAWI Graz, 8010 Graz, Austria; Field of Excellence
BioHealth, University of Graz, 8010 Graz, Austria;
BioTechMed Graz, 8010 Graz, Austria; orcid.org/0000-
monodemethylated regioselectively to 6-desmethylpapaverine
2
j which was isolated and confirmed by 2D-NMR experi-
0
002-2151-6394; Email: wolfgang.kroutil@uni-graz.at
57
ments (see Supporting Information for details). Thus, the
enzymatic transformation allowed us to demethylate selectively
in one out of the four possible positions. The obtained
monodemethylated product 2j was demethylated further to the
didemethylated product 4′,6-didesmethylpapaverine 4j; thus,
the second slower demethylation step took place at the second
benzene ring of the molecule. Both demethylated products 2j
and 4j are valuable biomarkers which are used to improve the
Authors
Christopher Grimm − Institute of Chemistry, University of
Graz, NAWI Graz, 8010 Graz, Austria
Mattia Lazzarotto − Institute of Chemistry, University of Graz,
NAWI Graz, 8010 Graz, Austria
Simona Pompei − Institute of Chemistry, University of Graz,
NAWI Graz, 8010 Graz, Austria
Johanna Schichler − Institute of Chemistry, University of Graz,
NAWI Graz, 8010 Graz, Austria
58
detection time of the drug heroin. Since papaverine 1j is used
4
5,46
as a drug to relax smooth muscles
and to inhibit human
59
prostate cancer cell growth, the demethylated derivatives
may be tested for similar applications as well. Another natural
Nina Richter − ACIB GmbH, Petersgasse 14, 8010 Graz,
Austria, c/o Institute of Chemistry, 8010 Graz, Austria
1
0378
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Research Article
Judith E. Farnberger − Institute of Chemistry, University of
Graz, NAWI Graz, 8010 Graz, Austria; ACIB GmbH,
Petersgasse 14, 8010 Graz, Austria, c/o Institute of Chemistry,
(14) Prier, C. K.; Kosjek, B. Recent Preparative Applications of
Redox Enzymes. Curr. Opin. Chem. Biol. 2019, 49, 105−112.
(
15) Dong, J. J.; Fernandez-Fueyo, E.; Hollmann, F.; Paul, C. E.;
́
Pesic, M.; Schmidt, S.; Wang, Y.; Younes, S.; Zhang, W. Biocatalytic
8
010 Graz, Austria
Oxidation Reactions: A Chemist’s Perspective. Angew. Chem., Int. Ed.
Michael Fuchs − Institute of Chemistry, University of Graz,
NAWI Graz, 8010 Graz, Austria; orcid.org/0000-0001-
2
(
018, 57, 9238−9261.
16) Nestl, B. M.; Hammer, S. C.; Nebel, B. A.; Hauer, B. New
6
757-7638
Generation of Biocatalysts for Organic Synthesis. Angew. Chem., Int.
Ed. 2014, 53, 3070−3095.
Complete contact information is available at:
https://pubs.acs.org/10.1021/acscatal.0c02790
(17) Sun, H.; Zhang, H.; Ang, E. L.; Zhao, H. Biocatalysis for the
Synthesis of Pharmaceuticals and Pharmaceutical Intermediates.
Bioorg. Med. Chem. 2018, 26, 1275−1284.
Funding
(
18) Bucko, M.; Gemeiner, P.; Schenkmayerova, A.; Krajcovic, T.;
̌ ́ ̌ ̌
Austrian Science Fund (FWF), Project P30920-B21 and
P31276-B21.
Rudroff, F.; Mihovilovic,
technological Approach. Appl. Microbiol. Biotechnol. 2016, 100, 6585−
599.
19) Hagel, J. M.; Facchini, P. J. Dioxygenases Catalyze the O-
̌
M. D. Baeyer-Villiger Oxidations: Bio-
6
(
Notes
The authors declare no competing financial interest.
Demethylation Steps of Morphine Biosynthesis in Opium Poppy. Nat.
Chem. Biol. 2010, 6, 273−275.
ACKNOWLEDGMENTS
(20) Lanfranchi, E.; Trajkovic, M.; Barta, K.; de Vries, J. G.; Janssen,
́
■
(
D. B. Exploring the Selective Demethylation of Aryl Methyl Ethers
This study was financed by the Austrian Science fund
P30920-B21), which is gratefully acknowledged. M.L. and
with a Pseudomonas Rieske Monooxygenase. ChemBioChem 2019,
2
0, 118−125.
21) Mallinson, S. J. B.; Machovina, M. M.; Silveira, R. L.; Garcia-
Borras, M.; Gallup, N.; Johnson, C. W.; Allen, M. D.; Skaf, M. S.;
M.F. are grateful for a grant of the Austrian Science Fund
FWF, P 31276-B21). The following COMET center is
(
(
̀
thanked for initial funding: acib: Next Generation Biopro-
duction is funded by BMK, BMDW, SFG, Standortagentur
Tirol, Government of Lower Austria und Vienna Business
Agency in the framework of COMET - Competence Centers
for Excellent Technologies. The COMET-Funding Program is
managed by the Austrian Research Promotion Agency FFG.
Crowley, M. F.; Neidle, E. L.; Houk, K. N.; Beckham, G. T.; Dubois,
J. L.; McGeehan, J. E. A Promiscuous Cytochrome P450 Aromatic O-
Demethylase for Lignin Bioconversion. Nat. Commun. 2018, 9, 1−12.
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22) Reisky, L.; Buchsenschutz, H. C.; Engel, J.; Song, T.; Schweder,
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T.; Hehemann, J.-H.; Bornscheuer, U. T. Publisher Correction:
Oxidative Demethylation of Algal Carbohydrates by Cytochrome
P450 Monooxygenases. Nat. Chem. Biol. 2018, 14, 342−344.
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