Stereoconvergent Reduction of Activated Alkenes by a Nicotinamide Free Synergistic Photobiocatalytic System

Article abstract of DOI:10.1021/acscatal.0c02489

There is a growing interest in developing cooperative chemoenzymatic reactions to harness the reactivity of chemical catalysts and the selectivity of enzymes for the synthesis of nonracemic chiral compounds. However, existing chemoenzymatic systems with m

Full text of DOI:10.1021/acscatal.0c02489

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Article
Stereoconvergent Reduction of Activated Alkenes by a
Nicotinamide Free Synergistic Photobiocatalytic System
Yajie Wang, Xiaoqiang Huang, Jingshu Hui, Lam Tung Vo, and Huimin Zhao
ACS Catal., Just Accepted Manuscript • DOI: 10.1021/acscatal.0c02489 • Publication Date (Web): 24 Jul 2020
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ACS Catalysis
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Stereoconvergent Reduction of Activated Alkenes by a Nicotinamide
Free Synergistic Photobiocatalytic System
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1,2,3,4*
Yajie Wang , Xiaoqiang Huang , Jingshu Hui , Lam Tung Vo , Huimin Zhao
1Institute for Sustainability, Energy, and Environment, University of Illinois at Urbana-Champaign, Urbana, IL 61801
2Department of Chemical and Biomolecular Engineering, University of Illinois at Urbana-Champaign, Urbana, IL
6
1801
3Department of Chemistry, University of Illinois at Urbana-Champaign, Urbana, IL 61801
4Carl R. Woese Institute for Genomic Biology, University of Illinois at Urbana-Champaign, Urbana, IL 61801
*To whom correspondence should be addressed
Phone: (217) 333-2631. Fax: (217) 333-5052. E-mail: zhao5@illinois.edu.
KEYWORDS: Cooperative chemoenzymatic catalysis, biocatalysis, photoinduced electron transfer, photosensitized energy
transfer, selectivity, alkene reduction
ABSTRACT: There is a growing interest in developing cooperative chemoenzymatic reactions to harness the reactivity of
chemical catalysts and the selectivity of enzymes for the synthesis of non-racemic chiral compounds. However, existing
chemoenzymatic systems with more than one chemical reaction and one enzymatic reaction working cooperatively are rare.
Moreover, the application of oxidoreductases in cooperative chemoenzymatic reactions is limited by the necessity of using
expensive and unstable redox equivalents such as nicotinamide cofactors. Here we report a light-driven cooperative
chemoenzymatic system comprised of a photoinduced electron transfer reaction (PET) and a photosensitized energy transfer
reaction (PEnT) with enzymatic reduction in one-pot to synthesize chiral building blocks of bioactive compounds. As a proof
of concept, ene-reductase was directly regenerated by PET in the absence of external cofactors. Meanwhile, enzymatic
reduction worked cooperatively with photocatalyst-catalyzed energy transfer that continuously replenished the reactive
isomer from the less reactive one. The whole system stereoconvergently reduced E/Z mixtures of alkenes to the enantiopure
products. Additionally, enantioselective enzymatic reduction worked competitively with photocatalyst-catalyzed racemic
background reaction and side reactions to channel the overall electron flow to the single enantiopure product. Such a light-
driven cooperative chemoenzymatic system holds great potential for asymmetric synthesis using inexpensive petroleum or
biomass derived alkenes.
Enzymes have been increasingly used as catalysts for
chemical synthesis in both academia and industry owing to
their high selectivity and mild reaction conditions.
cofactors NAD(P)H of enzymes (Figure 1b). The
transformation with multiple cooperative chemoenzymatic
reactions is rare (Figure 1c), but attractive since it largely
1
-4
8
Notably, there is a growing interest in developing
cooperative chemoenzymatic processes that combine the
high selectivity of enzymes with the diverse reactivity of
mimics the simultaneous reactions catalyzed by compatible
and selective enzymes to synthesize complex metabolites in
vivo in a highly efficient manner and has great potential to
11
5-10
chemical catalysts.
enzymatic reactions,
Unlike building artificial multistep
performing cooperative
precisely control the selective synthesis of abiotic chemicals
1
2
in a clean and cost-effective way. However, compared with
the single cooperative chemoenzymatic reaction, it is more
challenging to deal with compatability issues arising from
multilple chemical catalysts and enzymes in one-pot and
optimize the system by increasing the selectivity of the
desired products and reducing the formation of side
products.
chemoenzymatic synthesis is challenging because chemical
catalysis and biocatalysis are generally conducted under
very different conditions. Up to now, cooperative
chemoenzymatic reactions normally consist of a reversible
reaction catalyzed by a chemical catalyst in combination
with an irreversible enzymatic reaction (Figure 1a), such as
dynamic kinetic resolution of amines and alcohols5 or
chemical catalysts used to regenerate the nicotinamide
Recently, we developed a cooperative photoenzymatic
system by coupling alkene isomerization catalyzed by a
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photocatalyst with enzymatic reduction catalyzed by an
oxidoreductase called ene-reductase (ER) to synthesize
Figure 1. Cooperative chemoenzymatic reactions. a-c,
Types of cooperative chemoenzymatic reactions. ER is the
abbreviation of ene-reductase. “red” and “ox” indicate the
reduction and oxidation state of enzyme. d, Combination of PET,
PEnT, and enzymatic reduction of alkenes without using
NAD(P)H. The asterisk indicates the chiral center; Ar, aryl;
Chem Cat, chemical catalyst; PEnT, photosensitized energy
transfer reaction; PET, photoinduced electron transfer reaction
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enantiopure products.
Although oxidoreductases are
versatile catalysts for asymmetric synthesis due to their
intrinsic enantioselectivity and specificity,14
their
application in cooperative chemoenzymatic transformation
is limited by using expensive and unstable nicotinamide
cofactors such as reduced nicotinamide adenine
1
5
dinucleotide (phosphate), NAD(P)H. Various methods
such as enzymatic, chemical, electrochemical, and
photochemical approaches have been developed to
As a proof of concept, we sought to build a light-driven
stereoconvergent reduction of an isomeric mixture of
acceptor-substituted alkenes. Model substrate 2-
phenylbut-2-enedioic acid dimethyl ester 1 was used to set
up reactions to investigate suitable photocatalysts and
electron donors for the direct regeneration of FMN by PET
without compromising ERs’ selectivity (Table S1). YersER
was used since it exclusively reduced (E)-1 to dimethyl 2-
phenylsuccinate (1p) in high yield with excellent
enantiomeric excess (ee) in the presence of a glucose
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6-17
regenerate the reduced nicotinamide cofactors.
Among
them, the enzymatic method is still the only strategy
industrially employed due to its high turnover frequency
and is the most common methods used in chemoenzymatic
7
, 13
transformations to regenerate the oxidoreductases.
Inspired by recent works using photochemical strategies to
directly activate oxidoreductase without involving
1
8-25
+
NAD(P)H,
we aimed to develop a chemoenzymatic
dehydrogenase (GDH), NADP , and glucose for FMN
2
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27
system consisting of multiple reactions working
synergistically to stereoconvergently reduce a mixture of
alkenes to a single enantiopure product without using
nicotinamide cofactors (Figure 1c & d).
regeneration. Notably, although Eosin Y was used to
activate ER for asymmetric reduction of 2-
1
9
methylcyclohexone under an aerobic condition , it cannot
efficiently regenerate YersER for the more challenging
substrate (E)-1(Table 1, entry 1). Additionally, the excited
2
8
In this study, we describe a photobiocatalytic system that
consists of multiple reactions working in a synergistic
manner: photoinduced electron transfer (PET) for the
regeneration of the ligand of ER, flavin mononucleotide
state of Eosin Y is a strong reductant and can directly reduce
2
9
activated C=C bond to the racemic products, which
interfered with the enantioselective enzymatic reduction
step (entries 2-4 & 11). Unlike Eosin Y, flavins, especially
flavin adenine dinucleotide (FAD) could reactivate YersER
-
(
FMNH ), photosensitized energy transfer (PEnT) for alkene
isomerization from the less reactive one (typically Z-
alkenes) to reactive isomer (typically E-alkenes), and ER-
catalysed stereoconvergent reduction of C=C bond.
Meanwhile, the enzymatic reduction works competitively
with the photocatalyst-catalysed racemic background
reduction and other side reactions to ensure high yields and
high enantiomeric excess of the reduced products. This
represents a novel cooperative chemoenzymatic system in
which more than one chemical reaction works
cooperatively with enzymatic reaction, and chemical
catalysis and enzymatic catalysis benefit from each other
simultaneously.
in
the
presence
of
electron
donor
ethylenediaminetetraacetic acid (EDTA) to reduce (E)-1 to
1p in high yield with excellent ee (entry 5) comparable to
the enzymatic reduction with well-developed GDH
1
3
catalyzed NADPH regeneration system (Table S1).
However, the enzymatic system with FAD alone was not
able to reduce (Z)-1 to 1p in high yield (entry 12) because
very few (Z)-1 was isomerized to (E)-1 in the presence of
the electron donor EDTA (entries 13-14). This might be
because in the presence of EDTA, the photoexcited FAD
preferred to catalyze the photoredox reaction rather than
3
0-32
the energy transfer reaction.
Differently, 1% cationic
iridium complex [Ir(dmppy)
2
(dtbbpy)]PF (Ir-16) could
6
Cooperative Chemoenzymatic Reaction
isomerize (Z)-1 to (E)-1 efficiently in the presence of EDTA
Chem Cat
Enzyme
through PEnT mechanism (Figure S4, S5 & S14), but it could
a
b
Starting material
Intermediate
Enzyme
Product
-
not regenerate FMNH of YersER under blue light
Starting material
Product 1
illumination (entries 7-8 & 15-16). The enzymatic system
with 9.4% FAD and 1% (Ir-16) could efficiently reduce (Z)-
1 to 1p with 99% ee within 12 hours (entry 17, Figure S9),
NAD(P)+
NAD(P)H
Starting material
Product 2
-
where FAD executed electron transfer to regenerate FMNH
Chem Cat
and Ir-16 isomerized (Z)-1 to (E)-1 in the presence of blue
light. Little or no products were produced when the
reactions were performed without YersER but under blue
light (entry 18) or in the dark condition (entry 19). We
further tested the stability of photocatalysts by increasing
the concentration of (Z)-1 up to 20 mM while keeping the
total amount of photocatalysts (0.47 mM FAD and 0.05 mM
Ir-16) and enzyme (0.025 mM) unchanged. The yield of 1p
dropped to 26% and all unreduced 1 was E isomers (Table
S4). Adding more enzymes or FAD in the system after 24
hours did not improve the yield further, which indicated the
degradation and damage of YersER and FAD, respectively.
However, the low yield was mainly due to the low turnover
Chem Cat
c
Starting material
Intermediate
ERred
Starting material
Product 1
ERox
Product 2
Chem Cat
d
Ir(III)-catalyzed
R1
Ar
R1
Ar
R1
*
Ar
PEnT
Ene-reductase
R2
Blue light
R2
FAD-
catalyzed
PET
R2
Blue light
up to 90% yield
99% ee
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rate of YersER. Further increasing the YersER to 0.1 mM
reduction of less reactive isomers, either Z or E, to enantiopure
products with high yields and ee’s could be a strong proof of
the above-mentioned criteria 3 for a successful light-driven
enzymatic reduction system. As shown in Figure 2, our system
could convert unreactive Z isomers of aryl-diesters with either
electron withdrawing groups (Z)-2 and (Z)-3 or electron
donating group (Z)-4 to reduced products 2p, 3p and 4p with
high yields and at good to excellent ee’s with FAD and Ir-16 as
photocatalysts, EDTA as electron donors and different ERs.
The light-driven enzymatic system would also give high yields
and enantioselectivities with alkenes containing diverse
combinations of functional groups, including -cyano-,
unsaturated ester (Z)-6, -cyano-, unsaturated ester (Z)-7 and
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improved the yield to 68% (Table S4). The more detailed
discussion can be found in SI.
Next, we evaluated the performance of the light-driven
enzymatic reduction system with 12 additional 2-aryl
1
3
substituted alkenes and their corresponding ERs that
preferentially reduce E isomers of 2 to 12 and Z isomers of 13
to the enantioenriched reduced product. A successful light-
driven enzymatic reduction system should consist of a
photocatalyst and an electron donor that can: 1) quickly
regenerate the enzymatic cofactor FMN without interfering
with enzymatic activity and selectivity; 2) isomerize the less
reactive isomer to the more reactive isomer; and 3) ensure
appropriate reaction kinetics where the cooperative enzymatic
reduction step must be much faster than the background
reactions including FAD catalyzed alkene reduction. Therefore,
we first tested the light-driven enzymatic reduction on
additional reactive isomers (Table S2) and the isomerization of
less reactive isomers in the presence of FAD, Ir-16, and EDTA
or TEOA under the blue light, respectively (Table S3). For all
tested ERs, FAD could efficiently catalyze PET to regenerate
ER-FMNred for enantioselective reduction of reactive alkene
isomers at high yields and ee’s. For all tested substrates, less
reactive isomers could be isomerized to active isomers under
the blue light and in the presence of FAD. However, additional
Ir-16 was still preferred to achieve faster isomerization and
obtain more active isomers at the photostationary phase.
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(E/Z)-8, cyanoketone (Z)-9, -ketone-, unsaturated ester (Z)-
10, -ketone-, unsaturated ester (Z)-11, amidoacrylate (Z)-
12 and trifluoromethylcyanate (E)-13. Except for (Z)-6, for
which CaCl in TEOA solution was used as electron donor, all
2
other reactions were performed in 100 mM sodium phosphate
buffer at pH 7.4, with EDTA as the electron donor. For (Z)-10,
2
CaCl in TEOA solution can result in the reduced product at
relatively lower yield 65% but excellent ee (>99%). (E/Z)-5p
can undergo enzymatic reduction with FAD as the single
photocatalyst by using EDTA as the electron donor and under
blue light irradiation. Without ene-reductases, racemates and
side products were generated for most of the substrates. The
enantioenriched products that were obtained from the light-
driven enzymatic reduction system have the potential to be
transformed into a variety of biologically active molecules and
valuable synthetic intermediates as illustrated in our previous
Although it is not straightforward to measure the kinetics of
every chemical reaction occurring in the system, enzymatic
1
3
study.
Table 1. Reaction development and condition optimization
O
O
O
O
a
0
.5% YersER , Photocatalyst,
O
O
O
blue light
O
O
O
or
b
Buffer , 10% DMSO (v/v%),
N , ~15 h, RT
O
O
2
(
E)-1
(Z)-1
(R)-1p
Yield of
e- donor
ee of
1p
Entry
Substrate
Enzyme
Photocatalyst
E/Zc
1p
1d
2
3
4
5
6
7
8
9
(E)-1
(E)-1
(E)-1
(E)-1
(E)-1
(E)-1
(E)-1
(E)-1
(E)-1
(E)-1
(Z)-1
(Z)-1
(Z)-1
(Z)-1
(Z)-1
(Z)-1
(Z)-1
(Z)-1
(Z)-1
YersER
YersER
YersER
1% Eosin Y
1% Eosin Y
9.4% Eosin Y
1% Eosin Y
9.4% FAD
9.4% FAD
1% Ir-16
TEOA
TEOA
TEOA
TEOA
EDTA
EDTA
EDTA
EDTA
EDTA
EDTA
TEOA
EDTA
EDTA
-
34%
75%
60%
78%
86%
0%
-
-
-
63%
47%
0%
99%
-
-
-
99%
-
4%
43%
-
-
-
-
-
-
-
-
YersER
-
YersER
-
0%
0%
83:17
82:18
-
88:12
-
1% Ir-16
YersER 9.4% FAD & 1% Ir-16
74%
3%
50%
40%
0%
0%
0%
0%
88%
2%
10
-
9.4% FAD & 1% Ir-16
9.4% Eosin Y
9.4% FAD
11
12
YersER
YersER
0
1
1
1
1
1
1
3
4
5
6
7
8
-
-
9.4% FAD
9.4% FAD
1% Ir-16
1% Ir-16
7:93
83:17
82:18
85:15
-
YersER
-
EDTA
EDTA
EDTA
EDTA
EDTA
YersER 9.4% FAD & 1% Ir-16
99%
-
-
-
-
9.4% FAD & 1% Ir-16
85:15
0
e
19
various
0%
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aWithout specifications, all % means molar percentage, bSolution with 200 mM triethanolamine (TEOA), 10
1
2
3
4
5
6
7
8
9
1
1
1
1
1
1
1
1
1
1
2
2
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2
2
2
2
2
2
2
3
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3
3
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5
5
5
5
5
5
5
5
5
6
c
mM CaCl
2
at pH 7.5 or solution with 25 mM EDTA, 100 mM sodium phosphate buffer (KPi), at pH 7.2. The E/Z
d
e
ratio of the remaining substrates after reaction. Aerobic reaction. Control reactions were performed under
dark with FAD, Ir-16 or FAD & Ir-16, respectively.
(w/ or w/o) 0.5% ER, 9.4% FAD,
Ar
R1
R2
Ar
R1
(
w/ or w/o) 1% Ir-16, blue light
*
25 mM EDTA, 100 mM KPi at pH 7.2
R2
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
(or 10 mM CaCl , 200 mM TEOA at pH 7.5)
2
1-13
10% DMSO (v/v%),
1p-13p
N , 15 h, RT
2
MeO
F
CF3
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
1p
2p
3p
4p
FAD & Ir-16, EDTA
FAD & Ir-16, EDTA
FAD & Ir-16, EDTA
FAD & Ir-16, EDTA
YersER: 82% yield, 99% ee XenB: 85% yield, 99% ee
YersER: 83% yield, 95% ee YersER: 80% yield, 98% ee
w/o: 3% yield, 64% conv.
O
w/o: 11% yield, 35% conv.
w/o: 2% yield, 10% conv.
w/o: 0% yield, 0% conv.
N
O
N
O
O
O
O
O
O
O
N
Cl
5
p
O
6p
7p
8p
FAD, EDTA
FAD & Ir-16, TEOA
FAD & Ir-16, EDTA
FAD & Ir-16, EDTA
OYE2: 82% yield, 90% ee
w/o: 6% yield, 53% conv.
OPR1: 77% yield, >99% ee TOYE: 64% yield, 93% ee OYE2: 94% yield, 95% ee
w/o: 0% yield, 67% conv. w/o: 14% yield, 74% conv. w/o: 9% yield, 96% conv.
N
CF3
O
O
O
O
O
O
O
O
O
O
O
N
N
9
p
13p
1
0p
11p
FAD & Ir-16, EDTA
12p
FAD & Ir-16, EDTA
FAD & Ir-16, EDTA
FAD & Ir-16, EDTA
FAD & Ir-16, EDTA
OYE2: 78% yield, 92% ee OPR1: 92% yield, 93% ee YersER: 74% yield, 91% ee OPR1: 60% yield, >99% ee OYE2: 78% yield, 89% ee
w/o: 40% yield, 60% conv. w/o: 79% yield, 95% conv. w/o: 3% yield, 24% conv. w/o: 7% yield, 100% conv. w/o: 1% yield,76% conv.
Figure 2. Substrate scope of light-driven, photoenzymatic reduction of less or non-reactive alkenes of isomers to
enantioenriched products. Substrate 5 is a mixture of isomers with 62:38 E/Z ratio and 8 is a mixture of isomers with 23:77
E/Z ratio where Z isomers cannot be reduced by ERs for both cases. The starting material of 13 is the E isomer. The starting
materials of other substrates are Z isomers. The yields of 7p, 8p, and 13p were determined by NMR, while the yields of others
were determined by GC-MS. Abbreviations: w/o: without adding enzymes; conv.: conversion.
Our light-driven cooperative enzymatic system is able to
fully convert non-reactive or less reactive alkene isomers
that are usually the major products from organic synthesis
to enantiopure products without using external cofactors. It
is also able to stereoconvergently reduce mixtures of E/Z
alkenes in the tested substrates, such as a 62:38 E/Z mixture
of 5 and 23:77 E/Z mixture of 8, to the reduced products
with high yields and ee’s. In the presence of an electron
donor, more than half of the substrates only have 60% or
less reactive isomers generated at the photostationary
phase. The cooperative enzymatic reductions of those
substrates such as (Z)-7 and (E)-13 shown in Figure 3
highlighted the advantage of a cooperative system over two
sequential reactions. The photoisomerization of non-
reactive isomer (Z)-7 or (E)-13 with Ir-16 resulted in E/Z
mixtures in which active isomers were less than 10%. As a
result, low yields were observed if isomerization and
reduction were performed in a sequential manner (Figure
3). In this study, ERs preferentially reduce E isomers rather
than Z isomers to the enantioenriched products with the R
configuration for most cases, but OYE2 selectively reduces
(Z)-13 to (S)-13p with 89% ee. So, another advantage of the
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ACS Catalysis
cooperative system is that the dynamic equilibrium enables
V and -1.315 versus SCE for (Z)-9 and (Z)-10, respectively).
However, under blue light, FAD mediated photoreduction of
activated alkenes may occur with electron donor and result
in the reduced racemic products (Figure 2, 9p and 10p).
Additionally, without adding ERs, the substrate is relatively
unstable in the presence of the photocatalysts and blue light
irradiation. Most of the substrates were consumed with less
than 10% racemic target products generated (Figure 2, 1p,
1
2
3
4
5
6
7
8
9
the isomerization of either E or Z isomer with simultaneous
enzymatic reduction of the Z or E respectively to the
enantioenriched product in high yields.
3
7
Furthermore, in our light-driven cooperative enzymatic
system, the enzymatic reduction works not only
cooperatively
with
the
photocatalyst-catalyzed
isomerization reaction (Figure 4, route 2), but also
competitively with photoinduced racemic reduction (route
5-8p & 10p). Based on the time course study of light-driven
cooperative enzymatic reduction of (Z)-1 versus reactions
without YersER (Figure S9 & S10), It showed that the rate of
route 2 was much faster than that of route 1 and other
background reactions, which ensure the high yield and ee of
the reduced product. Generally speaking, with ERs, all other
substrates should be also preferentially reduced by the
1
) and other background reactions (Supporting Information
GC-MS traces). Under illumination, FAD is excited to high-
redox-potential FAD that is capable of oxidizing EDTA to
1
1
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0
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0
*
form semi-quinones, FADH Synproportionation of two
FADH generates fully reduced flavin FADH
2
that could
proportionate with FMN further in ene-reductase to
-
33-34
2
regenerated ER-FMNH into enantioenriched products
regenerate ER-FMNH (route 2, Figures S13).
2
FADH is a
3
8
through hydride transfer mechanism (route 2 & Figure 2).
moderate reductant (E1/2 = ~ -0.6 V versus saturated
calomel electrode (SCE))35-36 and thermodynamically
unable to transfer electron(s) to the substrate (E1/2 = -1.055
Sequential isomerization and reduction
N
O
N
N
9.4% FAD
O
O
1
% Ir-16
0.5% OYE2
O
O
O
blue light
25 mM EDTA, 100 mM KPi
buffer, pH 7.2
blue light, N2,
15 h, RT
Cl
Cl
Cl
(23:77 E/Z)-8
E:Z = 6:94
8p: 30% yield
10% DMSO, N2, 15 h, RT
9
.4% FAD
CF3
CF3
CF3
N
1% Ir-16
0.5% OYE2
blue light
blue light, N2,
15 h, RT
2
5 mM EDTA, 100 mM KPi
N
N
buffer, pH 7.2
(E)-13
10% DMSO, N2, 15 h, RT
E:Z = 97:3
13p: 23% yield
Concurrent/cooperative isomerization and reduction
N
O
N
O
O
0
.5 mol% OYE2, 9.4% FAD, 1% Ir-16
O
25 mM EDTA, 100 mM KPi buffer, pH 7.2
10% DMSO, N2, 15 h, RT, blue light
Cl
Cl
(
23:77 E/Z)-8
8p: 82% yield, 90% ee
CF3
CF3
N
0
.5 mol% OYE2, 9.4% FAD, 1% Ir-16
2
5 mM EDTA, 100 mM KPi buffer, pH 7.2
10% DMSO, N2, 15 h, RT, blue light
N
(E)-13
13p: 78% yield, 89% ee
Figure 3. Comparison of sequential isomerization and enzymatic reduction versus cooperative isomerization and reduction.
Route 1: photoinduced PET
Ar R1
rac-p
R2
2
e- + H+
FAD
Ar R1
Blue light
R2
E or Z
Route 2: Cooperative photoenzymatic reduction
Ar R1
R2
FADH-
ER_FMNH-
(R) or (S)-p
2
e- + H+
PET
Ar R1 Blue light
Ar R1
Blue light
FAD
ER_FMN
R2
R2
PEnT
Reactive isomer
Nonreactive isomer
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Figure 4. Proposed pathways: FAD-catalyzed directed electron transfer illustrated in route 1 versus cooperative photoenzymatic
reduction illustrated in route 2.
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In conclusion, we developed a light-driven cooperative
chemoenzymatic system to synthesize value-added chiral
molecules from a mixture of alkenes without the use of
expensive external nicotinamide cofactors. Under blue light
background racemic reduction and other side reactions to
ensure the high yields and ee’s of the products. More
generally, this study demonstrates the feasibility of building
cooperative chemoenzymatic reactions consisting of more
than one chemical reaction and one enzymatic reaction, as
well as the potential of combining photocatalysts with
-
irradiation, FAD regenerates FMNH ERs by directly
transferring electrons from cheap electron donors to the
FMN, and Ir-16 isomerizes the unreactive isomer to the
reactive isomer for enzymatic reduction through the energy
transfer machinery. Meanwhile, cooperative enzymatic
reduction competes with photocatalyst-catalyzed direct
oxidoreductases to develop
a wide range of new
cooperative chemoenzymatic transformations without
adding extra expensive nicotinamide cofactors.
0
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3
4
5
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9
0
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3
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9
0
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.
.
Straathof, A. J. J., Transformation of biomass into commodity
chemicals using enzymes or cells, Chem. Rev. 2014, 114,
ASSOCIATED CONTENT
1
871-1908.
Ciriminna, R.; Pagliaro, M., Green chemistry in the fine
chemicals and pharmaceutical industries, Org. Process. Res.
Dev. 2013, 17, 1479-1484.
AUTHOR INFORMATION
Corresponding Author
5. Verho, O.; Bäckvall, J.-E., Chemoenzymatic dynamic kinetic
resolution: powerful tool for the preparation of
A
Huimin Zhao - Department of Chemical and Biomolecular
Engineering, Univeristy of Illinois at Urbana-Champaign, 215
RAL, 600 S. Mathews Avenue, Urbana, IL 61802. Email:
zhao5@illinois.edu
enantiomerically pure alcohols and amines, J. Am. Chem. Soc.
2015, 137, 3996-4009.
Wang, Y.; Zhao, H., Tandem reactions combining biocatalysts
and chemical catalysts for asymmetric synthesis, Catalysts
2016, 6, 194-216.
6
.
7. Wang, Y.; Ren, H.; Zhao, H., Expanding the boundary of
biocatalysis: design and optimization of in vitro tandem
catalytic reactions for biochemical production, Crit. Rev.
Biochem. Mol 2018, 53, 115-129.
8. Rudroff, F.; Mihovilovic, M. D.; Gröger, H.; Snajdrova, R.; Iding,
H.; Bornscheuer, U. T., Opportunities and challenges for
combining chemo- and biocatalysis, Nat. Catal. 2018, 1, 12-
Author Contributions
YW and HZ conceived the work, designed and conducted
experiments, interpreted the data and wrote the manuscript.
HS, XH, and LV performed partial of the experiments. All
authors reviewed and approved the manuscript.
Funding Sources
2
2.
9
.
Denard, C. A.; Huang, H.; Bartlett, M. J.; Lu, L.; Tan, Y. C.; Zhao,
H. M.; Hartwig, J. F., Cooperative tandem catalysis by an
organometallic complex and a metalloenzyme, Angew. Chem.
Int. Ed. 2014, 53, 465-469.
This work was supported by the U.S. Department of Energy,
Office of Science, Office of Biological and Environment
Research, under award number DE-SC001842. Some of this
data was collected in the IGB Core on a 600MHz NMR funded
by NIH grant number S10-RR028833
10. Huang, X.; Cao, M.; Zhao, H., Integrating biocatalysis with
chemocatalysis for selective transformations, Curr. Opin.
Chem. Biol. 2020, 55, 161-170.
Supporting Information
1
1. Lee, S. Y.; Kim, H. U.; Chae, T. U.; Cho, J. S.; Kim, J. W.; Shin, J. H.;
Kim, D. I.; Ko, Y.-S.; Jang, W. D.; Jang, Y.-S., A comprehensive
metabolic map for production of bio-based chemicals, Nat.
Catal. 2019, 2, 18-33.
The Supporting Information is available free of charge on the
ACS Publications website.
1
2. Gröger, H., Metals and metal complexes in cooperative
catalysis with enzymes within organic-synthetic one-pot
processes. In Cooperative Catalysis, 2015; pp 325-350.
Figures S1-S14 and Tables S1-S4 , materials and methods,
detailed optimization studies, experimental procedures,
mechanistic rationales, GC-MS spectra, HPLC spectra and NMR
spectra.
13. Litman, Z. C.; Wang, Y.; Zhao, H.; Hartwig, J. F., Cooperative
asymmetric reactions combining photocatalysis and
enzymatic catalysis, Nature 2018, 560, 355-359.
14. Hollmann, F.; Arends, I. W. C. E.; Holtmann, D., Enzymatic
reductions for the chemist, Green. Chem. 2011, 13, 2285-
2314.
ACKNOWLEDGMENT
Prof. Kurt Faber is acknowledged for the gift of plasmid
pET21a-OPR1. Prof. Uwe T. Bornscheuer is acknowledged for
the gift of plasmid pGaston-XenB. Prof. Nigel S. Scrutton is
acknowledged for the gift of plasmid pET21b_TOYE. Jianan Li
and Linzixuan Zhang are acknowledged for their help in
protein purification.
1
5. Wu, H.; Tian, C.; Song, X.; Liu, C.; Yang, D.; Jiang, Z., Methods for
the regeneration of nicotinamide coenzymes, Green. Chem.
2013, 15, 1773-1789.
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6. Liu, W.; Wang, P., Cofactor regeneration for sustainable
enzymatic biosynthesis, Biotechnol. Adv. 2007, 25, 369-84.
7. van der Donk, W. A.; Zhao, H., Recent developments in
pyridine nucleotide regeneration, Curr. Opin. Biotech. 2003,
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