Production of enantiomerically enriched chiral carbinols using whole-cell biocatalyst

Article abstract of DOI:10.1080/10242422.2020.1837782

Biocatalytic asymmetric reduction of ketone is an efficient method for the production of chiral carbinols. The study indicates selective bioreduction of different ketones (1–8) to their respective (R)-alcohols (1a–8a) in low to high selectivity (0- >99%) with good yields (11–96%). In this work, whole-cell of Lactobacillus kefiri P2 catalysed enantioselective reduction of various prochiral ketones was investigated. (R)-4-Phenyl-2-butanol 2a, which is used as a precursor to antihypertensive agents and spasmolytics (anti-epileptic agents), was obtained using L kefiri P2 in 99% conversion and 91% enantiomeric excess (ee). Moreover, bioreduction of 2-methyl-1-phenylpropan-1-one substrate 8, containing a branched alkyl chain and difficult to asymmetric reduction with chemical catalysts as an enantioselective, to (R)-2-methyl-1-phenylpropan-1-ol (8a) in enantiomerically pure form was carried out in excellent yield (96%). The gram-scale production was carried out, and 9.70 g of (R)-2-methyl-1-phenylpropan-1-ol (8a) in enantiomerically pure form was obtained in 96% yield. Also especially, the yield and gram scale of (R)-2-methyl-1-phenylpropan-1-ol (8a) synthesised through catalytic asymmetric reduction using the biocatalyst was the highest report so far. The efficiency of L kefiri P2 for the conversion of the substrates and ee of products were markedly influenced by the steric factors of the substrates. This is a cheap, clean and eco-friendly process for production of chiral carbinols compared to chemical processes.

Full text of DOI:10.1080/10242422.2020.1837782

Biocatalysis and Biotransformation
ISSN: (Print) (Online) Journal homepage: https://www.tandfonline.com/loi/ibab20
Production of enantiomerically enriched chiral
carbinols using whole-cell biocatalyst
Yasemin Baydaş , Erbay Kalay & Engin Şahin
To cite this article: Yasemin Baydaş , Erbay Kalay & Engin Şahin (2020): Production of
enantiomerically enriched chiral carbinols using whole-cell biocatalyst, Biocatalysis and
Biotransformation, DOI: 10.1080/10242422.2020.1837782
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BIOCATALYSIS AND BIOTRANSFORMATION
https://doi.org/10.1080/10242422.2020.1837782
RESEARCH ARTICLE
Production of enantiomerically enriched chiral carbinols using whole-cell
biocatalyst
a
b
c
Yasemin Bayda s¸ , Erbay Kalay and Engin S¸ ahin
a
b
Faculty of Engineering, Department of Food Engineering, Bayburt University, Bayburt, Turkey; Kars Vocational School, Kafkas
c
University, Kars, Turkey; Faculty of Health Sciences, Department of Nutrition and Dietetics, Bayburt University, Bayburt, Turkey
ABSTRACT
ARTICLE HISTORY
Biocatalytic asymmetric reduction of ketone is an efficient method for the production of chiral
carbinols. The study indicates selective bioreduction of different ketones (1–8) to their respective
Received 22 June 2020
Revised 27 August 2020
Accepted 12 October 2020
(R)-alcohols (1a–8a) in low to high selectivity (0- >99%) with good yields (11–96%). In this work,
whole-cell of Lactobacillus kefiri P2 catalysed enantioselective reduction of various prochiral
ketones was investigated. (R)-4-Phenyl-2-butanol 2a, which is used as a precursor to antihyper-
tensive agents and spasmolytics (anti-epileptic agents), was obtained using L kefiri P2 in 99%
conversion and 91% enantiomeric excess (ee). Moreover, bioreduction of 2-methyl-1-phenylpro-
pan-1-one substrate 8, containing a branched alkyl chain and difficult to asymmetric reduction
with chemical catalysts as an enantioselective, to (R)-2-methyl-1-phenylpropan-1-ol (8a) in
enantiomerically pure form was carried out in excellent yield (96%). The gram-scale production
was carried out, and 9.70 g of (R)-2-methyl-1-phenylpropan-1-ol (8a) in enantiomerically pure
form was obtained in 96% yield. Also especially, the yield and gram scale of (R)-2-methyl-1-phe-
nylpropan-1-ol (8a) synthesised through catalytic asymmetric reduction using the biocatalyst
was the highest report so far. The efficiency of L kefiri P2 for the conversion of the substrates
and ee of products were markedly influenced by the steric factors of the substrates. This is a
cheap, clean and eco-friendly process for production of chiral carbinols compared to chemical
processes.
KEYWORDS
Asymmetric reduction;
whole-cell biocatalysts;
Lactobacillus kefiri; chiral
carbinol; biocatalytic
transformation
GRAPHICAL ABSTRACT
Introduction
chiral specific catalysts that are derived from transition
metals such as Rh-complexes with different nitrogen
containing compounds, chiral Lewis acid, metal-ligand
complexes and oxazaborolidine (Touchard et al. 1999;
He et al. 2014; Matsunami et al. 2018). However, there
are several drawbacks associated with chemical proc-
esses such as requirement of expensive chiral ligands
and hazardous metals, harsh conditions, low conver-
sion and low enantioselectivity, and formation of
byproducts. In addition to these chemical method,
several procedures are available for obtaining optically
pure alcohols like enzymatic resolution and catalytic
reduction of ketones with biocatalysts ( S¸ ahin 2020a).
Biocatalytic methods can offer highly selective, envir-
onmentally benign and energy effective solution for
production of optically active compounds ( S¸ ahin and
Dertli 2019; S¸ ahin 2020b). Biocatalytic asymmetric
reduction of prochiral ketones was reported to give
>99% theoretical conversion with excellent ee as com-
pared to other catalytic processes (Goldberg et al.
Chirality is important in living organisms due to the
asymmetric nature of basic molecular building blocks,
such as amino acids and sugars (Patel 2013).
Enantiopure secondary alcohols possess significant
importance as precursors for synthesis of complex
active pharmaceutical intermediates, agrochemicals
and other fine chemicals (Devendran and Yadav 2014;
Gandomkar et al. 2015). In terms of biological effects,
enantiomers of chiral compounds generally behave
quite differently. Since most drugs act as single enan-
tiomers, the synthesis of enantiomerically pure com-
pounds is extremely important. The functional groups
of chiral secondary alcohols can be easily converted to
other functional groups without racemation (Hollmann
et al. 2011). Several chemical processes are used to
synthesise secondary alcohols such as chromatography
separation, enantioselective crystallisation and asym-
metric reduction of prochiral substrate using different
CONTACT Engin S¸ ahin
esahin@bayburt.edu.tr
Faculty of Health Sciences, Department of Nutrition and Dietetics, Bayburt University, 69000,
Bayburt, Turkey
Supplemental data for this article can be accessed here.
ß 2020 Informa UK Limited, trading as Taylor & Francis Group

2
Y. BAYDAŞ ET AL.
2
007). Enantioselective bioreduction can be carried
chiral alcohols with this L kefiri P2 using the optimisa-
tion conditions we obtained using the model sub-
strate acetophenone in our previous study (Baydas¸
et al. 2020). Moreover, to the best of our knowledge,
it is the first report showing that (R)-2-methyl-1-phe-
nylpropan-1-ol 8a is obtained as the enantiopure form
using biocatalyst in the highest yield and maximum
amount. In addition, the effects of different groups in
substrates on selectivity and transformation were eval-
uated. The current study offers a practical method for
preparation of chiral secondary alcohols.
out by using either isolated enzymes or whole-cells.
The bioreduction using microbial whole-cells as bioca-
talysts are advantageous than the purified enzymes,
since the former contains multiple reductase enzymes
and can accept a wide variety of unnatural substrates
and synthesise necessary co-factors needed for bio-
transformation in-situ (Mandal et al. 2004). Enzymes
usually require expensive co-factors for their activity,
whereas whole-cell biocatalysts do not need them
since they themselves have sufficient amount of co-
factors. The use of whole-cell biocatalysts avoids a
number of expensive methods required for isolation
and purification of specific enzymes, and enzymes are
also stable within the cells (Patel et al. 2004). The
whole-cell biocatalysts during asymmetric reduction
reaction is considered to be better than the purified
enzymes (Rocha et al. 2009). Moreover, discovering
new microbial strains is necessary to meet the
demand of whole-cell biocatalyst in the industry.
There are a limited number of effectively useful
Lactobacillus kefiri in the production of chiral carbinols
which have been described in the literature. For
instance, pure ADH enzyme isolated from Lactobacillus
kefiri was used as biocatalyst for asymmetric reduction
of aromatic ketones and different prochiral ketones to
corresponding chiral secondary alcohols with high ee
and conversion (Weckbecker and Hummel 2006). Ethyl
Materials and methods
General
The substrates, solvents and the growth medium of
bacteria (MRS) were purchased from Fluka and Sigma-
Aldrich. Purification of 1a–8a were carried out by col-
umn chromatography and the alcohols were obtained
using ethyl acetate/hexane: (15:85, v/v) solvent mix-
ture. Progress of reaction was checked by Thin layer
chromatography (TLC), using ethyl acetate: hexane
(10:90, v/v) as the mobile phase. All the racemic alco-
hols (1a–8a) were prepared by reducing the corre-
sponding ketones with sodium borohydride in
methanol. HPLC analysis was performed on an Agilent
chromatograph (Model no: 1260). The product charac-
terisation was determined by Bruker NMR spectros-
copy (Bruker Ltd., Germany). Bellingham þ Stanley
(S)-4-chloro-3-hydroxybutanoate with high ee and
yield was obtained by Amidjojo et al. using
Lactobacillus kefiri as a whole-cell biocatalyst (Amidjojo
and Weuster-Botz 2005). Asymmetric bioreduction of
(ADP220, 589 nm) spectropolarimeter was used for the
optical rotation of the product. Conversion was deter-
mined by the HPLC using comparison of the ketone
peak with the alcohol peak after HPLC analysis of the
crude product.
(2,5)-hexanedione to enantiomerically pure (5 R)-
hydroxyhexane-2-one (ee >99%) with whole-cell
immobilised Lactobacillus kefiri was carried out by Tan
et al (Tan et al. 2006). Whole-cell Lactobacillus kefiri
was not extensively studied for the asymmetric reduc-
tion of prochiral ketones to corresponding chiral sec-
ondary alcohols, which can be drug precursors.
Considering the value of chiral carbinols, it will be
increasingly important to identify biocatalysts that can
be employed in the asymmetric bioreduction of differ-
ent substrates. Thus in this work, we have investigated
Culture medium and bacterial strain
L kefiri P2 strain used in this study was previously iso-
lated from kefir and this strain was grown in MRS
broth as described previously (Bayda s¸ et al. 2020).
General procedure for asymmetric bioreduction
the reducing capacity of
ous substrates.
L
kefiri P2 on vari-
L kefiri P2 was added from its glycerol stock by inocu-
lation to 10 mL MRS medium (MgSO .7H O 11.5% (w/
4
2
Previous work shows that the L kefiri P2 is an
important catalyst in the asymmetric reduction of vari-
ous aromatic prochial ketones (Bayda s¸ et al. 2020).
Therefore, this study was aimed at increasing the sub-
strate profile that L kefiri P2 can reduce, using previ-
ously achieved optimised conditions. Various prochiral
substrates were reduced to corresponding secondary
v), K HPO 2 g/L, pepton [Oxoid] 10 g/L, yeast extract
2 4
2% glucose, [Difco] 5 g/L, C H NaO2.3H O 5 g/L, salt
2
3
2
solution [MgSO4.7H2O 11.5% (w/v), triamonium citrate
2 g/L], Tween 80 1 mL/L) followed by 48 h growth at
ꢀ
37 C. From this mixture, overnight grown bacterial
cells were inoculated to 100 mL MRS mixture at 10%
concentration and then pH was adjusted to 4.5

BIOCATALYSIS AND BIOTRANSFORMATION
3
using1M HCI. After adjusting the pH, the mixture was
incubated again at 25 C, 150 rpm in an incubator-
shaker for 2 h. Then, 1 mmol of substrates (1–8) were
Chattopadhyay 2016); HPLC conditions: Chiralcel OD
column, 254 nm, and flow rate: 1.0 mL/min, i-PrOH/n-
hexane 5:95, tR (R) 14.5, (S) 21.8 min. HPLC analysis
condition of ketone 2 is the same as alcohol (R)-2a
and retention time of substrate was determined
as 9.3 min.
ꢀ
added to the reaction medium and the reactions were
ꢀ
incubated again at 25 C, 150 rpm in an incubator-
shaker for 64 h. The supernatant was extracted with
CH Cl and saturated with NaCl, then the product was
(R)-1-(naphthalen-2-yl)ethanol (3a) (Wu et al.
2
2
1
obtained and tested as described previously (Baydas¸
et al. 2020). HPLC analysis was applied for the deter-
mination of the ee of the products and the yields
were determined following the purification process in
column chromatography.
2016): Colourless oil, H-NMR (400 MHz, CDCl
)
3
d ¼ 7.85 (m, 4H), 7.52 (m, 3H), 5.07 (q, J ¼ 6.5 Hz, 1H),
1
3
2.21 (bs, OH), 1.60 (d, J ¼ 6.4 Hz, 3H);
(100 MHz, CDCl
)) ) d ¼ 143.2, 133.3, 132.9, 128.3,
128.0, 127.7, 126.2, 125.8, 123.9, 123.8, 70.5, 25.2;
C-NMR
3
2
5
25
[
a]D ¼ þ30.6 (c 0.50, CH Cl ), 82% ee; Lit. [a]
¼
2
2
D
þ37.0 (c 0.50, CH Cl , 99% ee for R enantiomer) (Wu
2
2
Gram scale synthesis of (R)-2-methyl-1-
phenylpropan-1-ol (8a)
et al. 2016); HPLC conditions: Chiralcel AS-H column,
30 nm, flow rate: 1.0 mL/min, i-PrOH/n-hexane 3:97, tR
2
L kefiri P2 was added from its glycerol stock by inocu-
(R) 19.7, (S) 23.4 min. HPLC analysis condition of
ketone 3 is the same as alcohol (R)-3a and retention
time of substrate was determined as 15.8 min.
lation to 10 mL MRS medium followed by 48 h growth
ꢀ
at 37 C. From this mixture, overnight grown bacterial
cells were inoculated to 2 L MRS medium at 10% con-
centration and incubation for 2 h under optimisation
conditions. Then the pH of the mixture was adjusted
to 4.5 by 1 M HCI. Following the 2 h of incubation,
substrate 8 (10 g) was added to the mixture and incu-
(R)-cyclohexyl(phenyl)methanol (4a) (Carlos et al.
2015): White solid, M.p.: 64–66 C; H-NMR (400 MHz,
ꢀ
1
CDCl ) d ¼ 7.36–7.28 (m, 5H), 4.39 (d, J ¼ 7.2 Hz, 1H),
3
1
3
2.01–1.61 (m, 6H), 1.42–0.94 (m, 6H);
C-NMR
(100 MHz, CDCl ) d ¼ 143.6, 128.2, 127.4, 126.6, 79.4,
3
ꢀ
25
bated on an incubator-shaker at 25 C, 150 rpm for
45.0, 29.3, 28.8, 26.4, 26.1, 26.0; [a]
CH Cl ), 28% ee; Lit. [a]
¼ ꢁ11 (c 0.50,
D
25
D
64 h. The product was obtained from the culture
¼ ꢁ28 (c 0.50, CH Cl , %71
2
2
2
2
supernatant
purified
and
characterised
as
ee for R enantiomer) (Carlos et al. 2015); HPLC condi-
tions: Chiralcel OD-H column, 254 nm, flow rate:
1.0 mL/min, i-PrOH/n-hexane 1:99, tR (R) 25.5, (S)
19.9 min. HPLC analysis condition of ketone 4 is the
same as alcohol (R)-4a and retention time of substrate
was determined as 5.9 min.
described above.
(
R)-2-bromo-1-(naphthalen-2-yl)ethanol
(1a)
ꢀ
1
(
(
4
Kang et al. 2017): White solid, M.p.: 66-68 C, H-NMR
400 MHz, CDCl ) d ¼ 7.88–7.79 (m, 3H), 7.52–7.43 (m,
3
H), 5.04 (dd, J ¼ 4.1, 2.6 Hz, 1H), 3.72 (dd, J ¼ 5.4,
4
.1 Hz, 1H), 3.60 (dd, J ¼ 5.4, 2.6 Hz, 1H), 2.75 (d,
(R)-2,3-dihydro-1H-inden-1-ol (5a) (Guo et al.
13
ꢀ
1
J ¼ 2.6 Hz, 1H (OH));
C-NMR (100 MHz, CDCl )
2015): White solid, M.p.: 68–69 C; H-NMR (400 MHz,
3
d ¼ 135.0, 133.3, 128.4, 127.9, 127.8, 126.4, 126.3,
CDCl ) d ¼ 7.46–7.37 (m, 1H), 7.30–7.20 (m, 3H),
3
2
5
1
26.1, 125.2, 122.6, 72.8, 39.9; [a]
¼ þ15.4 (c 1.1,
5.29–5.20 (m, 1H),3.06–2.99 (m, 1H), 2.89–2.74 (m, 1H),
D
25
13
CHCl ), 32% ee; Lit. [a]
ee for R enantiomer) (Kang et al. 2017); HPLC condi-
¼ þ47.1 (c 1.1, CHCl , 98%
2.56–2.38 (m, 1H), 2.05–1.82 (m, 1H);
C-NMR
3
D
3
(100 MHz, CDCl ) d ¼ 145.0, 143.3, 128.3, 126.7, 124.9,
3
25
D
tions: Chiralcel AS-H column, 254 nm, flow rate:
124.2, 59.5, 35.9, 29.7; [a]
¼ ꢁ16.1 (c 0.88, CHCl ),
3
25
1
1
.0 mL/min, i-PrOH/n-hexane 5:95, tR (R) 18.7, (S)
6.2 min (Figure S10). HPLC analysis condition of
52% ee; Lit. [a]D ¼ ꢁ30.7 (c 0.88, CHCl , %98.9 ee
3
for R enantiomer) (Guo et al. 2015); HPLC conditions:
Chiralcel AS-H column, 220 nm, flow rate: 0.5 mL/min,
i-PrOH/n-hexane 1:99, tR (R) 51.3, (S) 36.3 min. HPLC
analysis condition of ketone 5 is the same as alcohol
(R)-5a and retention time of substrate was determined
as 34.6 min.
ketone 1 is the same as alcohol (R)-1a and retention
time of substrate was determined as 20.8 min
(
Supporting information).
R)-4-phenylbutan-2-ol
Chattopadhyay 2016): Colourless oil,
(
(2a)
(Salvi
and
H-NMR
1
(
2
(
400 MHz, CDCl ) d ¼ 7.29–7.21 (m, 5H), 3.83 (m, 1H),
(4-nitrophenyl)(phenyl)methanol
(Karthikeyan et al. 2010): White solid, M.p.: 76–78 C;
(6a)
3
ꢀ
.75–2.67 (m, 2H), 1.77–1.64 (M, 2H), 1.42 (s, 1H), 1.23
1
3
1
d, J ¼ 6.0 Hz, 3H);
C-NMR (100 MHz, CDCl ))
H-NMR (400 MHz, CDCl ) d ¼ 8.18 (dd, J ¼ 8.8 Hz, 2H),
3
3
25
d ¼ 142.0, 128.4, 125.8, 67.5, 40.8, 32.1, 23.6; [a]
¼
7.56 (d, J ¼ 8.8 Hz, 2H), 7.29–7.37 (m, 5H), 5.90 (s, 1H),
D
25
D
13
ꢁ
15.5 (c 0.57, CHCI ), 91% ee; Lit. [a]
¼ þ16.5 (c
2.50 (s, 1H);
C-NMR (100 MHz, CDCl ) d ¼ 150.7,
3
3
0
.57, CHCl , 96.4% ee for S enantiomer) (Salvi and
142.7, 128.9, 128.8, 128.4, 127.0, 126.7, 123.7, 75.5;
3

4
Y. BAYDAŞ ET AL.
2
5
25
[
0
a]D ¼ 0 (c 0.30, CHCI ), 0% ee; Lit. [a]
¼ þ57.7 (c
et al. 2007; Wei et al. 2011; Bosak et al. 2012).
Enantiopure alcohol 1a, which is 2-haloethanols, was
obtained by kinetic resolution of the corresponding
racemic alcohol 1a (Hiratake et al. 1988) and asym-
metric transfer hydrogenation of 2-halo ketones 1
with a chemical catalyst (Zhou et al. 2016). The L kefiri
P2 mediated bioreduction of substrate 1 was reduced
to the corresponding (R)-carbinol 1a in 65% yield and
with 32% ee (Table 1, entry 1). Bioreductive products
3
D
.30, CHCl , %93 ee for S enantiomer) (Karthikeyan
et al. 2010); HPLC conditions: Chiralcel OD-H column,
50 nm, flow rate: 0.9 mL/min, i-PrOH/n-hexane 20:80,
tR (R) 11.1, (S) 12.2 min. HPLC analysis condition of
ketone 6 is the same as alcohol 6a and retention time
of substrate was determined as 10.6 min.
3
2
(
R)-4-phenylbut-3-en-2-ol (7a) (Chen et al. 2017):
1
Yellow oil, H-NMR (400 MHz, CDCl ) d ¼ 7.39–7.27 (m,
3
5
H), 6.57 (d, J ¼ 15.8 Hz, 1H), 6.28 (d, J ¼ 15.9 Hz, 1H),
.48 (m, 1H), 2.6 (bs, 1H (OH)), 1.39 (d, J ¼ 6.4 Hz, 3H);
of ketones type Ar(CH )nCOR (n > 0, R ¼ alkyl) are syn-
2
4
thetically important because the aryl moiety of the
resultant chiral alcohols can be oxidatively cleaved to
furnish chiral hydroxyl acids (Carlsen et al. 1981),
which are present in various bioactive natural prod-
ucts (White and Amedio 1989). 4-Phenyl-2-butanol is
also important to the pharmaceutical industry because
it is used as a precursor to antihypertensive agents
and spasmolytics (anti-epileptic agents) (Liese et al.
2000). The reduction of 2 had been previously
reported using different microbial strain such as
Geotrichum candidum (Matsuda et al. 2006), recombin-
ant diketoreductase (Wu et al. 2009), and purified
ketoreductases (KREDs) (Cicco et al. 2018) with high
selectivity. The L kefiri P2 mediated bioreduction of
substrate 2, with two-atom spacer between the phenyl
and ketone groups, was reduced to the (R)-4-phenyl-
butan-2-ol 2a in 99% yield and with 91% ee (Table 1,
entry 2). The asymmetric synthesis of aryl methyl car-
binols, a highly versatile and fascinating group of
chiral building blocks for the synthesis of molecules
with desirable biological activities was carried out
extensively (Patel 2002; Panke and Wubbolts 2005).
Tozlu et al. reported that enantiomerically enriched
(S)-1-(naphthalene-2-yl)ethanol 3a using Weissella par-
amesenteroides was obtained with 72% ee and 77%
yield (Tozlu et al. 2019). Besides, the enantioselective
reduction of the prochiral aryl methyl ketone deriva-
tive 3 was performed with high selectivity, using dif-
ferent biocatalysts by many research groups (Maczka
and Mironowicz 2002; Yadav et al. 2002; Homann
et al. 2004; Muthineni et al. 2016). Here, (R)-1-(naph-
thalen-2-yl)ethanol 3a was obtained with L kefiri P2 in
82% ee and 68% yield (Table 1, entry 3). There are
numerous studies involving enantioselective reduction
of cyclohexyl (phenyl) methanone 4 with chemical cat-
alysts (Hayes et al. 2005; Bigler et al. 2015; Slagbrand
et al. 2015), but there are limited studies involving the
bio-reduction of this compound ( S¸ ahin et al. 2019).
Ema et al. reported that (S)-4a was obtained with 59%
ee by the lipase enzyme (Ema et al. 2009). Chartrain
et al. demonstrated that cyclohexyl(phenyl)methanone
4 is reduced to (R)-4a by 75% ee and 55% conversion
1
3
C-NMR (100 MHz, CDCl ) d ¼ 136.8, 133.7, 129.2,
3
25
D
1
28.6, 127.6, 126.5, 68.8, 23.4; [a]
¼ þ7.2 (c 1.0,
25
D
CHCl ), 22% ee; Lit. [a]
9% ee for S enantiomer) (Chen et al. 2017); HPLC
conditions: Chiralcel OD-H column, 254 nm, flow rate:
.0 mL/min, i-PrOH/n-hexane 10:90, tR (R) 9.2, (S)
4.1 min. HPLC analysis condition of ketone 7 is the
same as alcohol (R)-7a and retention time of substrate
was determined as 8.3 min.
R)-2-methyl-1-phenylpropan-1-ol (8a) (Yu et al.
017): Colourless oil, purified yield 96%, H NMR
¼ ꢁ32.6 (c 1.0, CHCl ) for
3
3
9
1
1
(
1
2
(
400 MHz, CDCl ) d ¼ 7.36–7.25 (m, 5H), 4.36 (dd,
3
J ¼ 6.8, 3.1 Hz, 1H), 2.00–1.90 (m, 1H), 1.87 (d,
J ¼ 3.1 Hz, 1H), 1.62 (bs, 1H, (OH)), 1.00 (d, J ¼ 6.8 Hz,
13
3
H), 0.80 (d, J ¼ 6.8 Hz, 3H); C NMR (100 MHz, CDCl )
3
d ¼ 143.6, 128.2, 127.4, 126.5, 80.0, 35.3, 19.0, 18.2;
2
D
5
[a]
¼ 41.6 (c ¼ 1, CHCl ) >99% ee; Lit. (R)-2-methyl-
3
20
D
1
9
-phenylpropan-1-ol, [a]
9%ee) (Yu et al. 2017); HPLC conditions: Chiralcel OD-
H column, 220 nm, flow rate: 1 mL/min, n-hexane/i-
PrOH 98:2, t (R) 13.8 min. HPLC condition of substrate
is the same as alcohol (R)-8a and retention time of
substrate was determined as 5.0 min.
¼ 41.6 (c ¼ 1, CHCl , for
3
R
8
Results and discussion
In this study, the biocatalytic reactions were carried
out using 1 mmol substrates (1–8) under optimised
conditions which is obtained in the previous study
(
Table 1). In our previous study, asymmetric reduction
reaction conditions were optimised using the model
substrate acetophenone with L kefiri P2 and optimisa-
tion conditions were obtained as pH 4.5, time 64 h,
ꢀ
temperature 25 C, agitation speed 150 rpm (Baydas¸
et al. 2020). Enantiomerically enriched chiral 2-haloe-
thanols are applied extensively, as these building
blocks can be readily converted into various b-adren-
ergic receptor agonists and blockers (Ye et al. 2015).
Nifenalol, pronethalol, metaproterenol, and fenoterol
are among important medicines prepared from aryl-
substituted 2-haloethanols (Kapoor et al. 2005; Jozwiak

BIOCATALYSIS AND BIOTRANSFORMATION
5
Table 1. Asymmetric bioreduction of various prochiral ketones (1–8) using L kefiri P2.
a
b
c
d
Entry
1
Substrate
Product
ee (%) (R)
Conversion(%)
68
Yield (%)
65
32
91
82
28
2
3
4
99
71
14
94
68
11
5
6
52
99
14
95
12
Racemic
7
8
22
94
91
96
>99
>99
a
a
b
Determined by HPLC using Chiral column, Determination of absolute configuration was carried out by comparison of the sign of
c
d
optical rotation relative to the values in the literature, The conversions were determined by chiral HPLC, isolated yield.
with yeast Candida magnolia (Chartrain et al. 1997). In
this study, cyclohexyl(phenyl)methanone was
reduced to (R)-cyclohexyl(phenyl)methanol 4a with
8% ee and 14% conversion (Table 1, entry 4). The
analog of indanol-(1S,2R)-1-amino-2-indanol is used as
a precursor in the production of Indinavir (CrixivanVR ),
which acts as the HIV protease inhibitor in antiretro-
viral therapy (M a˛ czka et al. 2019). Numerous biocata-
lysts were used for the stereoselective reduction of
the prochiral 1-indanone 5 having a cyclic structure,
however 1-indanol 5a was obtained at low yield with
high selectivity (Caron et al. 2005; Yadav et al. 2009;
Nagai et al. 2018). It has also been reported in the lit-
erature that fused cyclic ketones such as substrate 5
are difficult to reduce with biocatalysts (Sun et al.
activity, relaxes the bronchial musculature (Schmidt
et al. 2006; Magnus et al. 2007; Wujkowska et al.
2016). The asymmetric hydrogen transfer to diaryl
ketones were performed to form diarylmethanols with
high selectivity; however, these reactions have serious
drawbacks for large-scale production in their potential
application (Touge et al. 2016). Biocatalysts have been
demonstrated to be stereoselective in the reduction of
some diaryl ketones that are difficult to reduce with
chemical catalysts. Truppo et al. have shown that
many diaryl ketones consisting of mono and disubsti-
tuted benzophenones have been successfully reduced
to their respective diarylmethanols with moderate to
excellent selectivity and small scale by using commer-
cially available ketoreductase enzyme (Truppo et al.
2007). Sahin studied the reduction of a series of diaryl
aromatic ketones catalysed by whole-cell of C. zeyla-
noides P1, wherein he has obtained excellent ee and
yield ( S¸ ahin 2020c). When the asymmetric reduction of
biaryl ketone 6 with L kefiri P2, 6a was obtained with
racemate and low conversion (Table 1, entry 6). This
low conversion and selectivity can be explained by
4
2
2016). Here, substrate 5 was reduced to (R)-2,3-dihy-
dro-1H-inden-1-ol 5a in 99% conversion and with 52%
ee (Table 1, entry 5). Diaryl carbinols are important
synthetic building blocks in the manufacturing of
pharmaceuticals, such as (R)-orphenadrine, (R)-neobe-
nodine, (S)-cetirizine, carbinoxamine, and L-cloperas-
tine, which possesses antitussive and antiedemic

6
Y. BAYDAŞ ET AL.
the sterically large substrate. a, b-Unsaturated sec-
onder alcohol 7a is used as a precursor in the total
synthesis of Chatenaytrienin-2 that is a group of fatty
acid type natural products that shown to possess
interesting and important bioactivities, significantly
the antitumor effects, and growth inhibitory action
against multidrug-resistant cancer cells (Kunkalkar and
Fernandes 2019). Chemical chiral ligands are generally
used for preparing chiral allylic alcohols through asym-
metric 1,2-reduction of enones. As an alternative to
these chemical methods, effective enzymatic methods
have been developed for the preparation of this chiral
alcohols (Nishihara et al. 2017; Kadotani et al. 2019).
Among them, enzymatic kinetic resolution of racemic
alcohols and asymmetric reduction of enzyme-cata-
lysed prochiral ketones are the main approaches. The
theoretical maximum yield of the enzymatic kinetic
resolution is 50%, which greatly limits the application
of this method. Cai et al. described that bioreduction
of substrate 7 using Perakine Reductase as biocatalyst
was carried out to give (S)-carbinol 7a in >99% ee
and 60% yield (Cai et al. 2019). The L kefiri P2 medi-
ated bioreduction of substrate 7 was reduced to the
corresponding (R)-carbinol 7a in 91% yield and with
Figure 1. Gram scale synthesis of (R)-2-methyl-1-phenylpro-
pan-1-ol (8a).
of (R)-2-methyl-1-phenylpropan-1-ol 8a and this bioca-
talyst can be used industrially. Low conversion was
observed with the bulkier substrates 4 and 6 (Table 1,
entry 4, 6). The reason for the low conversion of sub-
strates 4 and 6 may be due to the low solubility of
these substrates in water. However, it was observed
that there were no changes in the conversion and ee
in using organic solvents such as 5% ethyl alcohol, iso-
propyl alcohol and DMSO under optimised conditions.
These results shows that solubility is not the cause for
low conversion and ee for these substrates. The low
conversion rate for these substrates can be explained
by the inability of bulky groups to interact with the
enzyme active site. When substrate 2 and 7 are com-
pared, it is seen that the conversion is high for both
substrates. However, the selectivity obtained in sub-
strate 2 is quite high compared to 7 (Table 1, entry 2,
22% ee (Table 1, entry 7). (S) or (R)-2-methyl-1-phenyl-
propan-1-ol (8) was synthesised in the high ee using
different chemical process such as asymmetric reduc-
tion of ketone with chiral ligand and asymmetric alkyl-
ation of the corresponding aldehyde (Ling et al. 2018;
Sato et al. 2000). However, there is only one study in
which 2-methyl-1-phenylpropan-1-one (8a) was
obtained in enantiomerically pure form reduced from
corresponding ketone by using biocatalyst in the lit-
erature ( S¸ ahin 2020d). The L kefiri P2 mediated biore-
7
). This shows that substrate 2 interacts better with
the enzyme active site. When the substrates 1 and 3
are compared, 1a was obtained with lower conversion
and ee. This observation can be explained in terms of
steric hindrance of the substituent. Alsafadi and co-
workers has previously reported a similar trend
(Alsafadi et al. 2017). These results show that the
reduction and selectivity efficiency of L kefiri P2 varies
depending on the steric activity of the substrates.
duction of substrate
corresponding (R)-8a in 96% yield and with >99% ee
Table 1, entry 8). Since 8 afforded excellent enantio-
8
was reduced to the
Conclusion
(
selectivity and conversion for the reduction on a small
scale, we decided to conduct the transformation of 8
to (R)-8a on a large scale to demonstrate the viability
of the present system as industrially feasible (Figure
In conclusion, we have investigated the use of L kefiri
P2 for the production of chiral carbinols with high ee
and yields. We have shown that L kefiri P2 isolated
from kefir effectively catalyses the enantioselective
reduction of a various ketones (1–8) to give the (R)-
form of carbinols (1a–8a) with up to 0–99% ee. (R)-2-
methyl-1-phenylpropan-1-ol 8a, which is difficult to
reduce with chemical catalysts as an enantioselective
in the literature, was synthesised in gram scale, excel-
lent yield and enantiomerically pure form using L kefiri
P2. These results showed that current process has sig-
nificant potential for the green synthesis of (R)-2-
methyl-1-phenylpropan-1-ol 8a at an industrial scale.
This efficient and eco-friendly method was found to
be a versatile and promising tool for the clean
1
). The best ee (>99%) of product and complete con-
version were achieved with 67.4 mmol/2L concentra-
tion of substrate 8 (Figure 1). Under optimised
conditions, substrate 8 (76.4 mmol, 10.0 g) was con-
verted to (R)-2-methyl-1-phenylpropan-1-ol 8a (9.70 g)
using L kefiri P2 in 96% yield with >99% ee and con-
version. Compared with the past report, which used
biocatalyst, 2-methyl-1-phenylpropan-1-one 8 was bio-
reduced to (R)-2-methyl-1-phenylpropan-1-ol 8a in
higher yield and gram scale. These results show that L
kefiri P2 is an important biocatalyst for the production

BIOCATALYSIS AND BIOTRANSFORMATION
7
production of chiral secondary alcohols. The results
are promising the suitability of L kefiri P2 as a valuable
biocatalyst for the synthesis of chiral carbinols of
pharmaceutical interest. At the same time, asymmetric
reduction studies of substrates that may be important
for the pharmaceutical industry with this biocatalyst
continue in our laboratory.
cyclohexylphenyl alcohol by the yeast Candida magnoliae
MY 1785. J Ferment Bioeng. 83(4):395–396.
Chen F, Zhang Y, Yu L, Zhu SJAC. 2017. Enantioselective
NiH/Pmrox-catalyzed 1, 2- reduction of a, b-unsaturated
ketones. Angew Chem. 129(8):2054–2057.
ꢀ
Cicco L, R ꢀı os-Lombard ꢀı a N, Rodr ꢀı guez-Alvarez MJ, Mor ꢀı s F,
ꢀ
Perna FM, Capriati V, Garc ꢀı a-Alvarez J, Gonz ꢀa lez-Sab ꢀı n J.
2
018. Programming cascade reactions interfacing biocatal-
ysis with transition-metal catalysis in deep eutectic sol-
vents as biorenewable reaction media. Green Chem.
20(15):3468–3475.
Acknowledgements
Devendran S, Yadav GD. 2014. Lipase-catalyzed kinetic reso-
lution of (±)-1-(2-Furyl) ethanol in nonaqueous media.
Chirality. 26(6):286–292.
Devendran S, Yadav GD. 2014. Microwave assisted enzymatic
kinetic resolution of (±)-1-phenyl-2-propyn-1-Ol in nona-
queous media. Biomed Res Int. 2014:482678–482679.
Ema T, Ura N, Yoshii M, Korenaga T, Sakai T. 2009. Empirical
method for predicting enantioselectivity in catalytic reac-
tions: demonstration with lipase and oxazaborolidine.
Tetrahedron. 65(46):9583–9591. -
_
The authors thanks Dr. Enes DERTLI (Yildiz Technical
University, Turkey) for provided the bactaria strain used in
this study.
Disclosure statement
No potential conflict of interest was reported by
the author(s).
Gandomkar S, Habibi Z, Mohammadi M, Yousefi M, Salimi S.
2015. Enantioselective resolution of racemic ibuprofen
esters using different lipases immobilized on epoxy-func-
tionalized silica. Biocatal Agric Biotechnol. 4(4):550–554.
Goldberg K, Schroer K, L u€ tz S, Liese A. 2007. Biocatalytic
Ketone reduction-a powerful tool for the production of
chiral alcohols-part I: processes with isolated enzymes.
Appl Microbiol Biotechnol. 76(2):237–248.
References
Alsafadi D, Alsalman S, Paradisi F. 2017. Extreme halophilic
alcohol dehydrogenase mediated highly efficient synthe-
ses of enantiopure aromatic alcohols. Org Biomol Chem.
15(43):9169–9175.
Amidjojo M, Weuster-Botz D. 2005. Asymmetric synthesis of
the chiral synthon ethyl (S)-4-chloro-3-hydroxybutanoate
using Lactobacillus Kefiri. Tetrahedron Asymmetry. 16(4):
Guo J, Chen J, Lu Z. 2015. Cobalt-catalyzed asymmetric
hydroboration of aryl ketones with pinacolborane. Chem
Commun (Camb). 51(26):5725–5727.
899–901.
Bayda s¸ Y, Dertli E, S¸ ahin E. 2020. Green synthesis of chiral
aromatic alcohols with Lactobacillus kefiri P2 as a novel
biocatalyst. Synth Commun. 50(7):1035–1045.
Bigler R, Huber R, Mezzetti A. 2015. Highly enantioselective
transfer hydrogenation of ketones with chiral (NH)2 P2
macrocyclic iron(II) complexes. Angew Chem Int Ed Engl.
Hayes AM, Morris DJ, Clarkson GJ, Wills MA. 2005. A class of
ruthenium(II) catalyst for asymmetric transfer hydrogena-
tions of ketones. J Am Chem Soc. 127(20):7318–7319.
He P, Zheng H, Liu X, Lian X, Lin L, Feng X. 2014.
Asymmetric Reduction of a-amino ketones with a KBH4
solution catalyzed by chiral Lewis acids . Chemistry.
54(17):5171–5174.
2
0(42):13482–13486.
Bosak A, Smilovic IG, Sinko G, Vinkovic V, Kovarik Z. 2012.
Metaproterenol, isoproterenol, and their bisdimethylcarba-
mate derivatives as human cholinesterase inhibitors. J
Med Chem. 55(15):6716–6723.
Cai S, Shao N, Chen Y, Li A, Pan J, Zhu H, Zou H, Zeng S,
Sun L, Zhao J. 2019. Enantioselective reduction of
a,b-unsaturated ketones and aryl ketones by perakine
reductase. Org Lett. 21(12):4411–4414.
Hiratake J, Inagaki M, Nishioka T, Oda J. 1988. Irreversible
and highly enantioselective acylation of 2-Halo- 1-aryle-
thanols in organic solvents catalyzed by a lipase from
pseudomonas fluorescens. J Org Chem. 53(26):6130–6133.
Hollmann F, Arends IWCE, Holtmann D. 2011. Enzymatic
reductions for the chemist. Green Chem. 13(9):2285–2314.
Homann MJ, Vail RB, Previte E, Tamarez M, Morgan B, Dodds
DR, Zaks A. 2004. Rapid identification of enantioselective
ketone reductions using targeted microbial libraries.
Tetrahedron. 60(3):789–797.
Carlos AMM, Contreira ME, Martins BS, Immich MF, Moro AV,
L u€ dtke DS. 2015. Catalytic asymmetric arylation of ali-
phatic aldehydes using
Tetrahedron. 71(8):1202–1206.
Carlsen PHJ, Katsuki T, Martin VS, Sharpless KB. 1981. A
greatly improved procedure for ruthenium tetroxide cata-
lyzed oxidations of organic compounds. J Org Chem.
a
B/Zn exchange reaction.
Jozwiak K, Khalid C, Tanga MJ, Berzetei-Gurske I, Jimenez L,
Kozocas JA, Woo A, Zhu W, Xiao R, Abernethy DR, et al.
2007. Comparative molecular field analysis of the binding
of the stereoisomers of fenoterol and fenoterol derivatives
to the beta2 adrenergic receptor. J Med Chem. 50(12):
2903–2915.
46(19):3936–3938.
Caron D, Coughlan AP, Simard M, Bernier J, Piche Y,
Chenevert R. 2005. Stereoselective reduction of ketones
by Daucus carota hairy root cultures. Biotechnol Lett.
Kadotani S, Nokami T, Itoh T. 2019. Enhanced activity and
modified substrate-favoritism of Burkholderia cepacia lip-
ase by the treatment with a pyridinium alkyl-PEG sulfate
ionic liquid. Tetrahedron. 75(4):441–447.
27(10):713–716.
Chartrain M, Mathre D, Reamer RA, Patel S, Shinkai I,
Greasham R. 1997. Asymmetric bioreduction of cyclohexyl-
phenyl ketone to its corresponding alcohol (þ)
Kang BC, Shin SH, Yun J, Ryu DH. 2017. Highly enantioselec-
tive hydrosilylation of ketones catalyzed by a chiral oxaza-
borolidinium ion. Org Lett. 19(23):6316–6319.

8
Y. BAYDAŞ ET AL.
Kapoor M, Anand N, Ahmad K, Koul S, Chimni SS, Taneja SC,
Patel RN. 2013. Biocatalytic synthesis of chiral alcohols and
amino acids for development of pharmaceuticals.
Biomolecules. 3(4):741–777.
Patel RN. 2002. Microbial/enzymatic synthesis of chiral inter-
mediates for pharmaceuticals. Enzyme Microb Technol.
31(6):804–826.
Patel RN, Goswami A, Chu L, Donovan MJ, Nanduri V,
Goldberg S, Johnston R, Siva PJ, Nielsen B, Fan J, et al.
2004. Enantioselective microbial reduction of substituted
Qazi GN. 2005. Synthesis of b-adrenergic blockers (R)-
(
-)-nifenalol and (S)-(þ)-sotalol via a highly efficient reso-
lution of bromohydrin precursor. Tetrahedron:
a
Asymmetry. 16(3):717–725.
Karthikeyan J, Jeganmohan M, Cheng C-H. 2010. Cobalt-cata-
lyzed addition reaction of organoboronic acids with alde-
hydes:
highly
enantioselective
synthesis
of
diarylmethanols . Chemistry. 16(30):8989–8992.
Kunkalkar RA, Fernandes RA. 2019. Protecting-group-free
total synthesis of chatenaytrienin-2. J Org Chem. 84(18):
acetophenones.
1247–1258.,
Tetrahedron
Asymmetry.
15(8):
1
2216–12220.
Rocha LC, Ferreira HV, Pimenta EF, Berlinck RGS, Seleghim
MHR, Javaroti DCD, Sette LD, Bonugli RC, Porto ALM.
2009. Bioreduction of alpha-chloroacetophenone by
whole cells of marine fungi . Biotechnol Lett. 31(10):
1559–1563.
S¸ ahin E. 2020a. Production of enantiopure chiral aryl hetero-
aryl carbinols using whole-cell Lactobacillus paracasei bio-
transformation. Synth Commun. 50(4):549–557.
Liese A, Seelbach K, Wandry C. 2000. Industrial biotransfor-
mations. New York: Wiley-VCH; p. 423.
Ling F, Nian S, Chen J, Luo W, Wang Z, Lv Y, Zhong W. 2018.
Development of ferrocene-based diamine-phosphine-sul-
fonamide ligands for iridium-catalyzed asymmetric hydro-
genation of ketones. J Org Chem. 83(18):10749–10761.
M a˛ czka W, Wi nꢀ ska K, Grabarczyk M, Galek R. 2019. Plant-
mediated enantioselective transformation of indan-1-one
and indan-1-ol. Catalysts. 9(10):844.
Maczka WK, Mironowicz A. 2002. Enantioselective hydrolysis
of 1-aryl ethyl acetates and reduction of aryl methyl
ketones using carrot, celeriac and horseradish enzyme sys-
tems. Tetrahedron Asymmetry. 13:2299–2302.
S¸ ahin E. 2020b. Synthesis of enantiopure (S)-6-chlorochro-
man-4-ol using whole-cell Lactobacillus paracasei biotrans-
formation. Chirality. 32(3):400–406.
S¸ ahin E. 2020c. Candida zeylanoides as whole-cell biocatalyst
to perform asymmetric bioreduction of benzophenone
derivatives. Synth Commun. 50(4):612–619.
Magnus NA, Anzeveno PB, Coffey DS, Hay DA, Laurila ME,
Schkeryantz JM, Shaw BW, Staszak MA. 2007. Optimized
catalytic enantioselective aryl transfer process gives access
to mGlu2 receptor potentiators. Org Process Res Dev.
S¸ ahin E. 2020d. First green synthesis of (R)-2-methyl-1-phe-
nylpropan-1-ol using whole-cell Lactobacillus paracasei
BD101 biotransformation. Biocatal Biotransform. 38(2):
138–143.
11(3):560–567.
S¸ ahin E, Dertli E. 2019. Biocatalyzed Enantiomerically Pure
Mandal D, Ahmad A, Khan MI, Kumar R. 2004.
Enantioselective bioreduction of acetophenone and its
analogous by the fungus Trichothecium sp. J Mol Catal B
Enzym. 27(2–3):61–63.
Production of (S)-Phenyl (thiophen-2-yl) methanol.
Heterocyclic Chem. 56(10):2884–2888.
S¸ ahin E, Serencam H, Dertli E. 2019. Whole cell application
of Lactobacillus paracasei BD101 to produce enantio-
merically pure (S)-cyclohexyl(phenyl)methanol . Chirality.
31(3):211–218.
J
Matsuda T, Yamagishi Y, Koguchi S, Iwai N, Kitazume T.
2006. An effective method to use ionic liquids as reaction
media for asymmetric reduction by Geotrichum candidum.
Tetrahedron Lett. 47(27):4619–4622.
Matsunami A, Ikeda M, Nakamura H, Yoshida M, Kuwata S,
Kayaki Y. 2018. Accessible Bifunctional oxy-tethered ruthe-
nium (II) catalysts for asymmetric transfer hydrogenation.
Org Lett. 20:213–5218.
Salvi NA, Chattopadhyay S. 2016. Laboratory scale-up synthe-
sis of chiral carbinols using Rhizopus arrhizus.
Tetrahedron. 27(4-5):188–192.
Sato I, Saito T, Soai K. 2000. Solvent-free catalytic enantiose-
lective addition of diethylzinc to aldehydes. Chem
Commun. 24(24):2471–2472.
Muthineni N, Arnipally MS, Bojja S, Meshram HM, Srivastava
AK, Adari BR. 2016. Green approach towards the synthesis
of chiral alcohols using functionalized alginate immobi-
lized Saccharomyces cerevisiae cells. J Mol Catal B Enzym.
Schmidt F, Stemmler RT, Rudolph J, Bolm C. 2006. Catalytic
asymmetric approaches towards enantiomerically enriched
diarylmethanols and diarylmethylamines. Chem Soc Rev.
35(5):454–470.
134:233–237.
Slagbrand T, Kivij €a rvi T, Adolfsson H. 2015. Bimetallic cataly-
Nagai T, Sakurai S, Natori N, Hataoka M, Kinoshita T, Inoue
H, Hanaya K, Shoji M, Sugai T. 2018. Synthesis of enantio-
merically enriched drug precursors and an insect phero-
mone via reduction of ketones using commercially
available carbonyl reductase screening kit "ChiralscreenVR
sis: asymmetric transfer hydrogenation of sterically hin-
dered ketones catalyzed by ruthenium and potassium.
ChemCatChem. 7(21):3445–3449.
Sun Z, Lonsdale R, Ilie A, Li G, Zhou J, Reetz MT. 2016.
Catalytic asymmetric reduction of difficult-to-reduce
ketones: triple-code saturation mutagenesis of an alcohol
dehydrogenase. ACS Catal. 6(3):1598–1605.
Tan AWI, Fischbach M, Huebner H, Buchholz R, Hummel W,
Daussmann T, Wandrey C, Liese A. 2006. Synthesis of
Enantiopure (5R)-Hydroxyhexane-2-One with Immobilised
Whole Cells of Lactobacillus Kefiri. Appl Microbiol
Biotechnol. 71(3):289–293.
OH". Bioorg Med Chem. 26(7):1304–1313.
Nishihara TT, Shiomi A, Kadotani S, Nokami T, Itoh T. 2017.
Remarkably improved stability and enhanced activity of a
Burkholderia cepacia lipase by coating with a triazolium
alkyl-PEG sulfate ionic liquid. Green Chem. 19(21):
5250–5256.
Panke S, Wubbolts M. 2005. Advances in biocatalytic synthe-
sis of pharmaceutical intermediates. Curr Opin Chem Biol.
Touchard F, Bernard M, Fache F, Lemaire M. 1999. Ureas and
thioureas as Rh-ligands for the enantioselective hydride
9(2):188–194.

BIOCATALYSIS AND BIOTRANSFORMATION
9
transfer reduction of acetophenone. J Mol Catal A Chem.
40(1):1–11.
Wu X, Wang Y, Ju J, Chen C, Liu N, Chen Y. 2009.
Enantioselective synthesis of ethyl (S)-2-hydroxy-4-phenyl-
butyrate by recombinant diketoreductase. Tetrahedron
Asymmetry. 20(21):2504–2509.
Wujkowska Z, Jarzy nꢀ ski S, Pieczonka AM, Le ꢀs niak S,
Rachwalski M. 2016. Highly enantioselective addition of
arylzinc reagents to aldehydes promoted by chiral aziri-
dine alcohols. Tetrahedron Asymmetry. 27(24):1238–1244.
Yadav JS, Nanda S, Reddy PT, Rao AB. 2002. Efficient enan-
tioselective reduction of ketones with Daucus carota root.
J Org Chem. 67(11):3900–3903.
1
Touge T, Nara H, Fujiwhara M, Kayaki Y, Ikariya T. 2016.
Efficient access to chiral benzhydrols via asymmetric trans-
fer hydrogenation of unsymmetrical benzophenones with
bifunctional oxo-tethered ruthenium catalysts. J Am Chem
Soc. 138(32):10084–10087.
Tozlu C, S¸ ahin E, Serencam H, Dertli E. 2019. Production of
enantiomerically enriched chiral carbinols using Weissella
paramesenteroides as a novel whole cell biocatalyst.
Biocatal Biotransform. 37(5):388–398.
Truppo MD, Pollard D, Devine P. 2007. Enzyme-catalyzed
enantioselective diaryl ketone reductions. Org Lett. 9(2):
Yadav SJ, Reddy BVS, Sreelakshmi C, Rao AB. 2009.
Enantioselective reduction of prochiral ketones employing
Sprouted Pisum sativa as biocatalyst. Synthesis. 2009(11):
1881–1885.
Ye Q, Cheng T, Zhao Y, Zhao J, Jin R, Liu G. 2015. One-pot
cascade hydration–asymmetric transfer hydrogenation as
a practical strategy to construct chiral b-adrenergic recep-
tor blockers. ChemCatChem. 7(12):1801–1805.
Yu J, Long J, Yang Y, Wu W, Xue P, Chung LW, Dong X-Q,
Zhang X. 2017. Iridium-catalyzed asymmetric hydrogen-
ation of ketones with accessible and modular ferrocene-
based amino-phosphine acid (f-Ampha) Ligands. Org Lett.
19(3):690–693.
Zhou F, Hu X, Gao M, Tanyu Cheng T, Liu G. 2016. An imida-
zolium-modified chiral rhodium/diamine functionalized
periodic mesoporous organosilica for asymmetric transfer
hydrogenation of a-haloketones and benzils in aqueous
medium. Green Chem. 18(20):5651–5657.
335–338.
Weckbecker A, Hummel W. 2006. Cloning, expression, and
characterization of an (R)-specific alcohol dehydrogenase
from Lactobacillus Kefiri. Biocatal Biotransform. 24(5):
380–389.
Wei S, Messerer R, Tsogoeva SB. 2011. Asymmetric synthesis
of b-adrenergic blockers through multistep one-pot trans-
formations involving in situ chiral organocatalyst forma-
tion. Chemistry. 17(51):14380–14384.
White JD, Amedio JC. 1989. Total synthesis of geodiamolide
A, a novel cyclodepsipeptide of marine origin. J Org
Chem. 54(4):736–738.
Wu W, Liu S, Duan M, Tan X, Chen C, Xie Y, Lan Y, Dong X-
Q, Zhang X. 2016. Iridium catalysts with f-amphox ligands:
asymmetric hydrogenation of simple ketones. Org Lett.
18(12):2938–2941.