Asymmetric bioreduction of keto groups of 4- and 5-Oxodecanoic acids/esters with a new carbonyl reductase

Article abstract of DOI:10.1016/j.catcom.2017.08.023

A novel carbonyl reductase from Serratia marcescens, SmCR, was successfully cloned and overexpressed in Escherichia coli. SmCR could catalyze the asymmetric reduction of long-chain keto acids/esters containing remote carbonyl groups, such as 4-oxo- and 5-oxodecanoic acids, yielding chiral γ- and δ-decalactones with high enantiopurity (up to 99% ee). This is the first report of enzymatic synthesis of (R)-γ- and (R)-δ-decalactones starting from γ-, δ-keto acids using free enzymes.

Full text of DOI:10.1016/j.catcom.2017.08.023

CatalysisCommunications102(2017)35–39
Contents lists available at ScienceDirect
Catalysis Communications
journal homepage: www.elsevier.com/locate/catcom
Short communication
Asymmetric bioreduction of keto groups of 4- and 5-Oxodecanoic acids/
esters with a new carbonyl reductase
Chao Zhang, Jiang Pan, Chun-Xiu Li, Yun-Peng Bai⁎, Jian-He Xu⁎
State Key Laboratory of Bioreactor Engineering, Shanghai Collaborative Innovation Center for Biomanufacturing, East China University of Science and Technology, 130
Meilong Road, Shanghai 200237, China
A R T I C L E I N F O
A B S T R A C T
Keywords:
A novel carbonyl reductase from Serratia marcescens, SmCR, was successfully cloned and overexpressed in
Escherichia coli. SmCR could catalyze the asymmetric reduction of long-chain keto acids/esters containing remote
carbonyl groups, such as 4-oxo- and 5-oxodecanoic acids, yielding chiral γ- and δ-decalactones with high en-
antiopurity (up to 99% ee). This is the first report of enzymatic synthesis of (R)-γ- and (R)-δ-decalactones starting
from γ-, δ-keto acids using free enzymes.
4-Oxodecanoic acid
5-Oxodecanoic acid
(R)-γ-Decalactone
(R)-δ-Decalactone
Carbonyl reductase
Asymmetric reduction
1. Introduction
In contrast to chemical catalysts, the asymmetric reduction of keto
acids/esters through biocatalysis is considered to be environmentally
Optically pure aliphatic hydroxy acids and their derivatives have
been extensively studied as versatile chiral building blocks for the
preparation of many valuable bioactive compounds and natural pro-
ducts [1–4]. For instance (R)-(+)-γ- and (R)-(+)-δ-decalactones, one
class of flavors and fragrances that are widely used in the food industry,
can be readily synthesized by the direct cyclization of (R)-4-hydro-
xydecanoic acid and (R)-5-hydroxydecanoic acid, respectively [5,6].
Because of their high application potential, the production of chiral
hydroxy acids has attracted increasing attention. For example, the hy-
drolysis of biopolymer polyhydroxyalkanoate (PHA) is one of the major
biotechnological sources of chiral hydroxy acids, and a lot of achieve-
ments have been made in this area [7,8]. In terms of synthesis, the
asymmetric reduction of keto acids has been demonstrated to be one of
the most efficient and atom economic routes to chiral hydroxy acids.
However, although many chemical catalysts have been developed in the
last few decades, the highly enantioselective reduction of remote car-
bonyl groups in keto acids (or esters) is still challenging because the
majority of the substrates that have been studied have been limited to
α-/β-aromatic or short-chain aliphatic keto acids (esters) [9–15]. Re-
cently, Lin and co-workers developed a chiral surfactant-type catalyst
for the asymmetric transfer hydrogenation of long-chain aliphatic keto
esters in water [16]. However, this method was not applied for keto
acids and the enantioselectivity was not satisfactory. Furthermore, the
transition metals employed are expensive and inappropriate for appli-
cations in the food industry.
friendly and highly stereoselective. In the early 1960s, the wild-type
Saccharomyces cerevisiae was found to be capable of converting γ- and δ-
keto acids into optically pure hydroxy acids [17,18]. Later, it was em-
ployed to produce chiral lactones that were confirmed to have the R
configuration, which is the enantiomer that is used widely in the food
industry [19–22]. However, attempts to clone and express the enzyme
that was responsible for the conversion from the genome of Sacchar-
omyces cerevisiae were not successful. Currently, nothing is known about
the exact enzyme catalyzing the reduction of the remote carbonyl
groups in long-chain alkyl substituted (R)-lactones, despite a huge
number of carbonyl reductases reported in the literature [23–28]. Re-
cently, a number of chemo- or chemoenzymatic methods for preparing
enantioenriched γ- and δ-lactones were reported; however, the sub-
strates were still limited to short-chain alkyl or aryl substituted keto
acids/esters [29–34].
In this work, we report a novel carbonyl reductase with high en-
antioselectivity toward γ- and δ- long-chain keto acids/esters and an
efficient enzymatic route for the synthesis of optically pure (R)-(+)-γ-
and (R)-(+)-δ-decalactones (Scheme 1). The benefit of using a carbonyl
reductase is that the molecular structure of the functional enzyme is
known. Therefore, the activity and stereoselectivity can be further en-
hanced by protein engineering, which is impossible to achieve by
whole-cell biocatalysis employing wild-type microorganisms.
⁎
Corresponding authors.
E-mail addresses: ybai@ecust.edu.cn (Y.-P. Bai), jianhexu@ecust.edu.cn (J.-H. Xu).
http://dx.doi.org/10.1016/j.catcom.2017.08.023
Received 4 June 2017; Received in revised form 8 August 2017; Accepted 15 August 2017
Availableonline18August2017
1566-7367/©2017ElsevierB.V.Allrightsreserved.

C. Zhang et al.
CatalysisCommunications102(2017)35–39
Scheme 1. Carbonyl reductase catalyzed asymmetric re-
duction of γ- and δ-keto acids/esters into chiral hydroxy
acids/esters and lactones.
2. Experimental
cured product was purified by column chromatography eluting with
petroleum ether and ethyl acetate (10:1).
2.1. Materials
4-Oxodecanoic acid, methyl 4-oxodecanoate, ethyl 4-oxodecanoate,
5-oxodecanoic acid, methyl 5-oxodecanoate and ethyl 5-oxodecanoate
were obtained from Xiamen Bestally Biotechnology Co., Ltd. (Fujian,
China). Racemic γ-decalactone and δ-decalactone were purchased from
TCI (Shanghai, China). All other chemicals and reagents were obtained
commercially. E. coli DH5α and E. coli BL21 (DE3) were used as the
cloning and expression hosts, respectively. Plasmid pET-28a (+) was
used for heterogeneous expression.
3. Results and discussion
3.1. Cloning and expression of carbonyl reductase
Previously, we discovered a carbonyl reductase (CpAR2) that can
efficiently reduce the ε-carbonyl group in ethyl 8-chloro-6-ox-
ooctanoate [28]. This enzyme was initially tested to transform 4-ox-
odecanoic acid, but the product was confirmed to be (S)-4-hydro-
xydecanoic acid, which was not the desired enantiomer. Because no
similar enzymes have been reported, we decided to search for new
carbonyl reductases from microbes. Thousands of single bacterial co-
lonies from environmental soil samples were screened, resulting in a
bacterial strain, Pseudomonas panipatensis, which could convert 4-ox-
odecanoic acid into (R)-4-hydroxydecanoic acid with 97% ee. A novel
carbonyl reductase was cloned from Pseudomonas panipatensis, desig-
nated as PpCR, and expressed by E. coli BL21. PpCR displayed a specific
activity of 1.44 U/g toward 4-oxodecanoic acid with 99% ee (Table 1,
entry 1).
To discover more enzymes, the gene sequence of PpCR was used as
the template to perform pBLAST searching in UniProt. On the basis of
the results, we selected 16 bacterial strains stored in our lab and cloned
the corresponding carbonyl reductases (SI, Table S1) that consist of a
toolbox of 20 recombinant enzymes expressed in E. coli BL21 (DE3).
These carbonyl reductases have moderate sequence identities (40–70%)
compared with the template enzyme. Of them, nine reductases ex-
hibited excellent stereoselectivity (> 99% ee) and various activities
(from 0.196 to 3.32 U/g protein), as shown in the asymmetric reduction
of 4-oxodecanoic acid (Table 1). SmCR (from Serratia marcescens),
which displayed the highest activity of 3.32 U/g and had a 47% amino
acid identity to PpCR, was chosen for further studies.
2.2. Cloning and expression of carbonyl reductase in E. coli
The genes of carbonyl reductases were amplified by PCR using the
primers listed in Table S1 (see Supporting information). The amplified
DNA were then inserted into expression plasmid pET-28a (+). The
recombinant plasmids were then transformed into E. coli BL21 (DE3).
The cells were cultivated at 37 °C in 100 mL LB medium containing
50 mg/L Kanamycin. The expression of encoding genes were induced
by the addition of IPTG to a final concentration of 0.2 mM at OD600 of
0.6. After addition of IPTG, the cultures were grown at 16 °C for another
24 h.
2.3. Enzyme assays
The reductase activity was determined by monitoring the decrease
in the absorbance of NADPH at 340 nm. The assay was performed in a
96-well half-area plate. Each reaction contained a final concentration of
0.1 mM NADPH, 0.2 mM substrate, 100 mM sodium phosphate buffer
(pH 7.0) and an appropriate amount of enzyme. Absorbance reading
were taken every 2 min at 30 °C for 60 min using a PowerWave XS2
spectrophotometer (BioTek, USA). One unit of enzyme activity was
defined as the amount of enzyme that catalyzed the oxidation of 1 μmol
NADPH per minute under above conditions.
Table 1
Enzyme screening for the reduction of 1a.
2.4. Preparative procedures
Entry
Enzyme
Amino acid identity (%)
Specific activity (U/g)a
ee (%)b
For cell-catalyzed reaction, the reaction mixture was composed of
0.2 mmol substrate, 1 mmol glucose, 0.05 mmol NADP+, 5 g wet cells
of E. coli/SmCR, 0.5 g lyophilized E. coli/BmGDH and 100 mL of sodium
phosphate buffer (100 mM, pH 6.0). For enzyme-catalyzed reaction,
substrate (25–75 mM), glucose (5 equivalents of substrate), 0.5 mM
NADP+, 150 mg/mL lyophilized cell-free extracts of E. coli/SmCR, and
10 mg/mL lyophilized E. coli/BmGDH were mixed in a 500 mL sodium
phosphate buffer (100 mM, pH 6.0). The reaction was performed at
30 °C and the pH was controlled at 6.0 with addition of 1.0 mol/L
NaOH solution. GC was used to monitor the reaction progress. After
16 h, the mixture was acidified to pH 2.0 with 20% H2SO4 and heated
at 90 °C for 2 h. The mixture was extracted with ethyl acetate, dried
over Na2SO4, filtered and concentrated under reduced pressure. The
1
2
3
4
5
6
7
8
9
PpCR
SmCR
LgCR
ArCR
CnCR
VpCR
AaCR
RpCR
CbCR
VbCR
100
47
51
56
63
56
56
65
63
66
1.44
3.32
2.76
2.67
> 99 (R)
> 99 (R)
> 99 (R)
> 99 (R)
> 99 (R)
> 99 (R)
> 99 (R)
> 99 (R)
> 99 (R)
> 99 (R)
1.53
0.838
0.658
0.490
0.451
0.196
10
a
Specific activity was determined spectrophotometrically in sodium phosphate buffer
(100 mM, pH 7.0) containing 2 mM substrate 1a, 0.1 mM NADPH, and a proper amount
of purified enzymes at 30 °C.
b
The ee values were determined by chiral GC analysis of the corresponding lactones.
36

C. Zhang et al.
CatalysisCommunications102(2017)35–39
3.2. Effects of pH and temperature on enzyme activity and stability
keto acid, from 75% to 99% ee (Table 2). SmCR showed the highest
enantioselectivity (99% ee) toward 4-oxodecanoic acid. This suggested
that the active pocket of SmCR may have a higher binding affinity to-
ward the keto ester substrate, which adopts a flexible conformation
during the reaction, leading to a higher activity but a lower stereo-
selectivity. The kinetic parameters were consistent with this assump-
tion, as SmCR has a lower Km toward the keto esters than toward the γ-
keto acid (Table 2). Furthermore, the kcat values of SmCR against the γ-
keto esters were one order of magnitude higher than those against the γ-
keto acids (Table 2), which results in higher catalytic efficiencies.
The same changes in activity and stereoselectivity were also ob-
served for the δ-keto acids/esters (Table 2, substrates 1d–f). However,
the position of the carbonyl group in the carbon chain also influenced
the catalytic efficiency, as the specific activity and specificity constant
(kcat/Km) of the δ-keto acids/esters were both lower than those of the
corresponding γ-keto acids/esters. Notably, the stereoselectivity of
SmCR toward methyl 5-oxodecanoate (1e) and ethyl 5-oxodecanoate
(1f) was reversed, as the reaction yielded more methyl (S)-5-hydro-
xydecanoate and ethyl (S)-5-hydroxydecanoate. For the reduction of
aryl substituted ketones, enzymes in the SDR family usually have two
pockets - the large pocket hosting the aromatic ring and the small
pocket hosting the alkyl side chain, which determines the face of the
hydride attack on the carbonyl group and the corresponding enzyme
stereoselectivity [35]. Therefore, the observed reversion of the se-
lectivity of SmCR toward 1e and 1f should be attributed to the substrate
binding in the two pockets. This issue is under investigation in our la-
boratory, which is beyond the scope of this paper.
To investigate the intrinsic properties of SmCR, the recombinant
enzyme was purified to homogeneity from the cell free extract of re-
combinant E. coli (SI, Fig. S1) with a Ni-NTA column and characterized
to determine the optimal catalytic conditions for the conversion of
substrate 4-oxodecanoic acid. The pH profile highlighted the maximum
activity was at pH 6.0 in sodium phosphate buffer (SI, Fig. S2 A). The
activity was found to be the highest at 40 °C, at which it was 30% faster
than at room temperature (SI, Fig. S2 B). We monitored the enzymatic
activity as a function of time and observed satisfactory half-lives of
90 h, 50 h and 15 h at 30 °C, 40 °C and 50 °C, respectively (SI, Fig. S2
C). Although SmCR is not comparable to other high thermostable en-
zymes in the short-chain dehydrogenases/reductases (SDR) family, its
already high activity at low temperature enables it to be a good can-
didate in industrial applications. In addition, its thermostability can be
further improved by protein engineering in the future.
3.3. Time course of the asymmetric reduction of 4-oxodecanoic acid
Subsequently, the asymmetric reduction of 4-oxodecanoic acid by E.
coli/SmCR was performed at 30 °C in a 10-mL reaction mixture. To
ensure a sufficient supply of NADPH, E. coli expressing a glucose de-
hydrogenase from Bacillus megaterium (E. coli/BmGDH) was added for
the regeneration of cofactor NADPH by catalyzing the oxidation of
glucose. Substrate 4-oxodecanoic acid was reduced into product (R)-4-
hydroxydecanoic acid in 12 h with 97% conversion, and after simple
workup (R)-4-hydroxydecanoic acid was readily cyclized into (R)-γ-
decalactone in 99% ee (SI, Fig. S2 D).
3.5. Chemoenzymatic preparation of (R)-(+)-γ- and (R)-(+)-δ-
decalactones
3.4. Substrate specificity
To the best of our knowledge, this is the first report of an isolated
carbonyl reductase that can reduce γ−/δ- carbonyl groups in long-
chain aliphatic keto acids/esters with high enantioselectivity. To fur-
ther demonstrate its advantage for the synthesis of optically pure chiral
lactones, we employed SmCR for the preparative synthesis of 3a and 3d
through a one-pot cascade chemoenzymatic route (Table 3). After the
asymmetric reduction, the reaction mixture was acidified with 20%
H2SO4 and heated for intramolecular cyclization to convert the corre-
sponding hydroxy acids into optically pure lactones. In a 100 mL pre-
parative experiment, 2 mM substrate 1a or 1d was transformed by the
whole-cell catalyst E. coli/SmCR. After 16 h (R)-γ-decalactone (3a) was
obtained in 99% ee and 79% yield, whereas (R)-δ-decalactone (3d) was
Of special interest, we focused on employing SmCR to asymme-
trically reduce aliphatic γ- and δ-keto acids/esters, which has not been
reported using isolated enzymes. Therefore, we explored and compared
the specific activity and kinetic parameters of SmCR toward substrates
1a–f, which contain carbonyl groups far from the carboxylate/ester
groups (Table 2). For the γ-keto acids/esters (substrates 1a–c), SmCR
shows the highest activity (156 U/g) toward ethyl 4-oxodecanoate (1c).
Interestingly, an increase in specific activity was observed when the
substrates were changed from γ-keto acids to methyl or ethyl γ-keto
esters (Table 2, column 5). In contrast, the enantiopurity of the (R)-
decalactone increased in the reverse order from the ethyl ester to the γ-
Table 2
Asymmetric reduction of γ-, δ-keto acids/esters with SmCR.
Substrate
n
R1
R2
Specific activity (U/g)a
Km (mM)
kcat (min−1
)
kcat/Km (min−1 mM−1
)
ee (%)b
1a
1b
1c
1d
1e
1f
1
1
1
2
2
2
C6H13
C6H13
C6H13
C5H11
C5H11
C5H11
H
3.32
143
156
2.07
101
114
1.26
0.659
0.528
1.86
1.69
1.12
0.128
4.68
4.89
0.124
4.52
3.89
0.102
7.10
9.26
0.066
2.67
3.47
99 (R)
90 (R)
75 (R)
95 (R)
31 (S)
40 (S)
CH3
C2H5
H
CH3
C2H5
a
Specific activity was determined spectrophotometrically in sodium phosphate buffer (100 mM, pH 7.0) containing 2 mM substrate, 0.1 mM NADPH, and an appropriate amount of
purified enzymes at 30 °C.
b
The ee values were determined by chiral GC analysis of the corresponding lactones.
37

C. Zhang et al.
CatalysisCommunications102(2017)35–39
Table 3
SmCR-catalyzed reduction of keto acids.
Entry
Substrate
Substrate loading (mM)
Catalyst loading (mg/mL)
Time (h)a
Conv. (%)a
Yield (%)b
ee (%)a
1
2
3
4
5
6
7
1a
1a
1a
1a
1d
1d
1d
2
50c
16
8
97
98
95
82
90
92
73
79 (3a)
77 (3a)
73 (3a)
74 (3a)
76 (3d)
75 (3d)
72 (3d)
> 99
> 99
> 99
> 99
95
25
50
75
2
50
75
150d
150d
150d
50c
16
24
16
16
24
150d
150d
95
95
a
Determined by GC analysis. The ee values were determined by chiral GC analysis of the corresponding lactones.
Yields are determined for lactones isolated after flash column chromatography.
b
c
Reaction conditions: substrate (2 mM), glucose (10 mM), NADP+ (0.5 mM), wet cells of E. coli/SmCR (50 mg/mL), lyophilized E. coli/BmGDH (5 mg/mL), 100 mL sodium phosphate
buffer (100 mM, pH 6.0), 30 °C.
d
Reaction conditions: substrate (25–75 mM), glucose (5 equivalents of substrate), NADP+ (0.5 mM), lyophilized cell-free extracts of E. coli/SmCR (150 mg/mL), lyophilized E. coli/
BmGDH (10 mg/mL), 500 mL sodium phosphate buffer (100 mM, pH 6.0), 30 °C.
harvested in 95% ee and 76% yield (Table 3, entries 1 and 5). Then, to
enhance the substrate loading, the preparative experiments were car-
ried out in the presence of a constant amount of lyophilized enzyme
powders (150 mg/mL) in 500 mL reaction systems. 25 mM 1a was
successfully transformed into 3a with 98% conversion and > 99% ee
after 8 h (Table 3, entry 2), which was more efficient than the cell-
catalyzed transformation. However, when the substrate loading was
further increased up to 50 and 75 mM, the conversion decreased to 95%
and 82%, respectively, although the reaction time was prolonged
(Table 3, entries 3 and 4). The same tendency was also observed for
preparing 3d of 95% ee, in which 92% and 73% conversion were ob-
tained for 50 mM and 75 mM 1d loading, respectively (Table 3, entries
6–7). As a reference, δ-keto acids have been reported not to undergo
asymmetric reduction with a chemical catalyst [10]. The recently de-
veloped chiral surfactant-type catalyst was also not applied for keto
acids [16]. In our work, we have demonstrated that the novel SmCR can
reduce the remote carbonyl groups in keto acids with high enantios-
electivity, which is difficult to achieve with chemical catalysts.
and Development of China (2016YFA0204300), National Natural
Science Foundation of China (Nos. 21505044, 21536004 & 21776085)
Shanghai Pujiang Program (15PJ1401200) and the Fundamental
Research Funds for the Central Universities (222201714026).
Appendix A. Supplementary data
Supplementary data to this article can be found online at http://dx.
doi.org/10.1016/j.catcom.2017.08.023.
References
[1] M.C. Warner, A. Nagendiran, K. Bogár, J.E. Bäckvall, Org. Lett. 14 (2012)
5094–5097.
[2] P. Kumar, N. Dwivedi, Acc. Chem. Res. 46 (2013) 289–299.
[3] A. Yajima, Tetrahedron Lett. 55 (2014) 2773–2780.
[4] J. Staroń, J.M. Dąbrowski, E. Cichoń, M. Guzik, Crit. Rev. Biotechnol. (2017) 1–14,
http://dx.doi.org/10.1080/07388551.2017.1332571.
[5] E. Brenna, C. Fuganti, F.G. Gatti, S. Serra, Chem. Rev. 111 (2011) 4036–4072.
[6] Y. Gounaris, Flavour Fragr. J. 25 (2010) 367–386.
[7] Q. Ren, K. Ruth, L. Thöny-Meyer, M. Zinn, Appl. Microbiol. Biotechnol. 87 (2010)
41–52.
[8] J. Radivojevic, S. Skaro, L. Senerovic, B. Vasiljevic, M. Guzik, S.T. Kenny, V. Maslak,
J. Nikodinovic-Runic, K.E. O'Connor, Appl. Microbiol. Biotechnol. 100 (2016)
161–172.
4. Conclusion
We have discovered a novel, robust and distinct carbonyl reductase
SmCR that can perform the asymmetric reduction of long-chain ali-
phatic γ- and δ-keto acids/esters with high enantioselectivity. In
500 mL gram-scale preparative experiments, 25–75 mM γ- and δ-keto
decanoic acids were reduced to (R)-hydroxy acids, which were readily
cyclized into the optically pure (R)-γ-decalactone in 99% ee and (R)-δ-
decalactone in 95% ee and 72–77% yields. The reduction of γ- and δ-
keto acids proceeded under mild conditions with a high conversion of
up to 98%, making SmCR a promising candidate for application as an
industrial biocatalyst. As the first isolated enzyme for such reaction,
SmCR not only provides a good base for further enzyme engineering but
it can also be used as a template to gain a better understanding of the
still largely unknown functional enzymes in eukaryotes such as
Saccharomyces cerevisiae. The sequence features of SmCR can also be
exploited to identify new and diverse enzymes to process relatively
longer aliphatic keto acids/esters containing remote carbonyl groups.
[9] K. Everaere, J.F. Carpentier, A. Mortreux, M. Bulliard, Tetrahedron Asymmetry 9
(1998) 2971–2974.
[10] P.V. Ramachandran, H.C. Brown, S. Pitre, Org. Lett. 3 (2001) 17–18.
[11] J.W. Yang, B. List, Org. Lett. 8 (2006) 5653–5655.
[12] D. Cartigny, K. Püntener, T. Ayad, M. Scalone, V. Ratovelomanana-vidal, Org. Lett.
12 (2010) 3788–3791.
[13] M.A. Ariger, E.M. Carreira, Org. Lett. 14 (2012) 4522–4524.
[14] C.G. Goodman, D.T. Do, J.S. Johnson, Org. Lett. 15 (2013) 2446–2449.
[15] J.M. Tukacs, B. Fridrich, G. Dibó, E. Szekely, L.T. Mika, Green Chem. 17 (2015)
5189–5195.
[16] Z.C. Lin, J.H. Li, Q.F. Huang, Q.Y. Huang, Q.W. Wang, L. Tang, D.Y. Gong, J. Yang,
J. Zhu, J.G. Deng, J. Organomet. Chem. 80 (2015) 4419–4429.
[17] G. Tuynenburg Muys, B. van der Ven, A.P. de Jonge, Nature 194 (1962) 995–996.
[18] A. Francke, Nature 197 (1963) 384–385.
[19] A. Francke, Biochem. J. 95 (1965) 633–640.
[20] M. Utaka, H. Watabu, A. Takeda, Chem. Lett. (1985) 1475–1476.
[21] M. Utaka, H. Watabu, A. Takeda, J. Organomet. Chem. 52 (1987) 4363–4368.
[22] Y. Naoshima, H. Hasegawa, T. Saeki, Agric. Biol. Chem. 51 (1987) 3417–3419.
[23] Y. Ni, J.H. Xu, Biotechnol. Adv. 30 (2012) 1279–1288.
[24] D. Kalaitzakis, J.D. Rozzell, S. Kambourakis, I. Smonou, Org. Lett. 7 (2005)
4799–4801.
[25] N.D. Shen, Y. Ni, H.M. Ma, L.J. Wang, C.X. Li, G.W. Zheng, J.H. Xu, Org. Lett. 14
(2012) 1982–1985.
Acknowledgments
[26] G.A. Applegate, R.W. Cheloha, D.L. Nelson, D.B. Berkowitz, Chem. Commun. 47
(2011) 2420–2422.
This work was financially sponsored by the National Key Research
38

C. Zhang et al.
CatalysisCommunications102(2017)35–39
[27] G.C. Xu, H.L. Yu, Z.J. Zhang, J.H. Xu, Org. Lett. 15 (2013) 5408–5411.
[28] Y.J. Zhang, W.X. Zhang, G.W. Zheng, J.H. Xu, Adv. Synth. Catal. 357 (2015)
1697–1702.
Symp. Ser. 1212 (2015) 59–75.
[32] T. Fisher, J. Pietruszka, Adv. Synth. Catal. 354 (2012) 2521–2530.
[33] T. Classen, M. Korpak, M. Schölzel, J. Pietruszka, ACS Catal. 4 (2014) 1321–1331.
[34] Y. Liu, Z. Sun, C. Huang, T. Tu, Chem. Asian. J. 12 (2017) 355–360.
[35] A. Dudzik, W. Snoch, P. Borowiecki, J. Opalinska-Piskorz, M. Witko, J. Heider,
M. Szaleniec, Appl. Microbiol. Biotechnol. 99 (2015) 5055–5069.
[29] A. Díaz-Rodríguez, W. Borzęcka, I. Lavandera, V. Gotor, ACS Catal. 4 (2014)
386–393.
[30] B. Hasdemir, Synth. Commun. 45 (2015) 1082–1088.
[31] E. Brenna, M. Crotti, F.G. Gatti, F. Parmeggiani, A. Pugliese, S. Santangelo, ACS
39