Laboratory scale-up synthesis of chiral carbinols using Rhizopus arrhizus

Article abstract of DOI:10.1016/j.tetasy.2016.01.008

Rhizopus arrhizus mediated bioreduction was optimized using acetophenone as a model substrate. Various parameters such as bio-processing conditions, reaction time, substrate concentration, temperature, and solvent carrier were studied. This optimized protocol was further exploited for scaled up bioreductions of various prochiral ketones. This study demonstrates the versatility of the fungus Rhizopus arrhizus as a biocatalyst to obtain chiral carbinols in good to excellent yields and selectivities.

Full text of DOI:10.1016/j.tetasy.2016.01.008

Tetrahedron: Asymmetry xxx (2016) xxx–xxx
Contents lists available at ScienceDirect
Tetrahedron: Asymmetry
journal homepage: www.elsevier.com/locate/tetasy
Laboratory scale-up synthesis of chiral carbinols using
Rhizopus arrhizus
⇑
Neeta A. Salvi , Subrata Chattopadhyay
Bio-organic Division, Bhabha Atomic Research Centre, Trombay, Mumbai 400 085, India
a r t i c l e i n f o
a b s t r a c t
Article history:
Rhizopus arrhizus mediated bioreduction was optimized using acetophenone as a model substrate.
Various parameters such as bio-processing conditions, reaction time, substrate concentration, tempera-
ture, and solvent carrier were studied. This optimized protocol was further exploited for scaled up biore-
ductions of various prochiral ketones. This study demonstrates the versatility of the fungus Rhizopus
arrhizus as a biocatalyst to obtain chiral carbinols in good to excellent yields and selectivities.
Ó 2016 Published by Elsevier Ltd.
Received 14 December 2015
Accepted 12 January 2016
Available online xxxx
1. Introduction
cellular environment. Moreover, the use of whole cell biocatalysts
avoids enzyme purification and cofactor addition.1
Chirality is important in living organisms due to the asymmet-
ric nature of basic molecular building blocks, such as amino acids
and sugars. Biocatalysis is a simple, mild, cost-effective, and eco-
friendly reagent in bio-organic synthesis and often displays high
regio-, stereo-, and enantioselectivity. For successful biotransfor-
mations, the substrate molecule should come in contact with the
enzymes present in the micro-organism in a way such that the cat-
alytic capability of the organism should remains unaffected by the
reaction conditions, since they determine the quality and the quan-
tity of the product.
The prediction of good bio-catalyst for a specific transformation
of a given substrate can be identified from small-scale test reac-
tions. This straightforward small-scale liquid fermentation is a
dynamic process, simple to set up, easy to run, and requires little
infrastructure, and so is inexpensive to conduct. For this, reaction
conditions have to be designed in such a way that it should allow
the transport of a reactant to catalytic sites with the highest solu-
bility in the reaction medium to enhance the permeability of the
cells to the reactant. From a synthetic perspective, it is necessary
to select experimental conditions that favor the production of the
desired enzyme catalyst to perform single and highly selective
reactions.
We selected Rhizopus arrhizus, a filamentous and versatile fun-
gus as a biocatalyst.2 In continuation with unoptimized biotrans-
formations with this fungus, we here report the optimization of
various parameters for the bioreduction of acetophenone 1 as a
model substrate. This protocol was further evaluated for the labo-
ratory scale bioreduction of other prochiral ketones.
2. Results and discussion
The bioreduction of acetophenone to the corresponding (R)- or
(S)-1-phenylethanol is one of the most common reactions in
organic chemistry. These chiral alcohols can be easily transformed
into other useful functional groups without racemization.3 The
effect of various parameters on the asymmetric reduction of ace-
tophenone was studied and the results obtained are discussed
below.
2.1. Effect of incubation time and bio-processing conditions
The bioreduction of acetophenone, 1 was studied at different
incubation periods using three different biotransformation
processes as described in the Experimental. All three processes
predominantly furnished (S)-1-phenylethanol, 1a without
significant variation in the enantiomeric excess of the product. As
summarized in Figure 1, it was observed that a better conversion
was obtained with 72 h grown culture. This indicates that the
cultivation of cells to a certain density before adding the substrate
is advantageous. This is because at optimum enzymatic activity,
the negative influence of the substrate on fungal growth can be
avoided. Thus the delayed addition of substrate might help to
Whole cell biocatalysts are advantageous as they are generally
inexpensive and more stable. They contain multiple dehydroge-
nases that are able to accept a broad range of unnatural substrates.
All enzymes and co-factors are well protected within their natural
⇑
Corresponding author.
E-mail address: nasalvi@barc.gov.in (N.A. Salvi).
http://dx.doi.org/10.1016/j.tetasy.2016.01.008
0957-4166/Ó 2016 Published by Elsevier Ltd.
Please cite this article in press as: Salvi, N. A. ; Chattopadhyay, S. Tetrahedron: Asymmetry (2016), http://dx.doi.org/10.1016/j.
tetasy.2016.01.008

2
N. A. Salvi, S. Chattopadhyay / Tetrahedron: Asymmetry xxx (2016) xxx–xxx
chloroform, and xylene were used as carrier solvents, provided
80
60
40
20
0
(S)-1-phenylethanol. This might be due to the toxic effect of
toluene, chloroform, and xylene to the organism, thus hampering
their reductase activity (Fig. 3). The maximum yield was obtained
when ethanol and DMSO were used as carrier solvents. However,
working with DMSO has operational complexities such as extrac-
tion of the product alcohols. On the other hand, ethanol, up to 2%
concentration, did not inactivate the fungal activity and was also
inexpensive. This also acts as an anti-bacterial agent and so was
found to be a biocompatible carrier solvent for biotransformation
studies. Thus ethanol was used as a suitable solvent for ketone sol-
ubility in the culture medium.
Growing cells
72h Grown cells
Resting cells
0
2
4
6
8
10 12 14 16 18 20
80
70
60
50
40
30
20
10
0
Incubation period (Days)
Figure 1. Comparison between bioreduction processes.
circumvent potential ketone toxicity to the microbes. As a result,
72 h grown culture and 8 days of incubation period were found
to be preferred conditions for this fungal bioreduction.
2.2. Effect of substrate concentration
The potential of R. arrhizus for bio-reduction of 1 was also stud-
ied using different substrate concentrations. As shown in Figure 2,
it was observed that as the substrate concentration increased, reac-
tivity decreased. A drastic decrease in the yield was noticed when
the concentration was beyond 200 mg/150 ml medium/flask. This
could be due to the reduction in the enzyme activity, suggesting
substrate toxicity. Hence 100–200 mg substrate/150 ml medium/
flask was found to be the optimum concentration.
Carrier solvents
Figure 3. Effect of carrier solvents.
100
80
60
40
20
0
2.4. Effect of temperature
In general, the rate of chemical reaction increases with an
increase in the reaction temperature. The reaction was therefore
carried out under different temperatures. The highest conversion
(77%) was observed at 24 °C, which then drastically dropped to less
than 15% at 37 °C and zero at 48 °C (Fig. 4). Thus the reduction was
significantly influenced by thermal induction and a temperature
between 24–28 °C was found to be optimum for bioreduction
and hence was recommended for the scale-up reaction.
0
100
200
300
400
500
Conc. mg/150 ml medium/Flask
Figure 2. Effect of substrate concentration.
80
60
40
20
0
2.3. Effect of organic solvent vehicles
In the biotransformation process, the substrate should be able
to pass through the cell membrane without being toxic to the
micro-organism.4 Most of the ketones are xenobiotic and poorly
water soluble. Hence, their reduction in aqueous media is ham-
pered due to low availability. To overcome this limitation, various
water miscible and water immiscible organic solvents were used as
solvent vehicles.
Acetophenone is insoluble in water, so various organic solvents
were used as solvent vehicles to dissolve it. The effects of these car-
rier solvents on the yield and the enantiomeric purity of the alco-
hol were studied. Almost all experiments, except when toluene,
24-25
28-29
37-38
48-49
Temperature °C
Figure 4. Effect of temperature.
Please cite this article in press as: Salvi, N. A. ; Chattopadhyay, S. Tetrahedron: Asymmetry (2016), http://dx.doi.org/10.1016/j.
tetasy.2016.01.008

N. A. Salvi, S. Chattopadhyay / Tetrahedron: Asymmetry xxx (2016) xxx–xxx
3
2.5. Scale-up biotransformation
context laboratory scale-up bioreduction of 3, using R. arrhizus
was carried out and furnished >99% enantiomerically pure (S)-6-
Fluorochroman-4-ol, 3a in 95.4% Yield.
With the optimum conditions in hand, we carried out the scale-
up bioreduction of acetophenone. The (S)-1-phenylethanol, 1a was
obtained in 76% yield (0.77 g) and with 83.4% enantiomeric purity.
The scope of this protocol was further extended with various
prochiral ketones, 2–7 (Chart 1) for the preparation of chiral carbi-
nols 2a–7a (Table 1). These chiral alcohols are key intermediates
for the synthesis of many pharmaceutical and agrochemical com-
pounds. As summarized in the Table 1, these substrates were easily
reduced to the corresponding chiral carbinols in good to excellent
yields and selectivities.
Bioreductive products of ketones type Ar(CH2)nCOR (n > 0,
R = alkyl) are synthetically important because the aryl moiety of
the resultant chiral alcohols can be oxidatively cleaved to furnish
chiral hydroxyl acids,13 which are present in various bioactive nat-
ural products.14 4-Phenyl-2-butanol is also important to the phar-
maceutical industry because it is used as a precursor to anti-
hypertensive agents and spasmolytics (anti-epileptic agents).15
The R. arrhizus mediated scale-up bioreduction of substrate 4, with
two-atom spacer between the phenyl and ketone groups, was
reduced to the corresponding (S)-carbinol 4a in 92.8% yield and
with 96.4% enantiomeric purity. Substrate 5, which possesses
one-atom spacer between the phenyl and ketone groups, was
reduced to (R)-carbinol 5a,2i the anti-Prelog product in 79.8% and
with 97% enantiomeric purity.
O
O
F
O
O
O
1
2
3
Chiral b-hydroxy esters are important building blocks for the
synthesis of a large number of bioactive intermediate and chiral
auxillaries.2f Cryptocarya acetates were isolated from the leaves
and bark of the South African plant, Cryptocarya latifolia, which
has long been noted for its medicinal properties.16 These range
from the treatment of headaches and morning sickness to that of
cancer, pulmonary diseases, and various bacterial and fungal infec-
tions.17 (S)-t-Butyl-3-hydroxybutyrate is an important chiral raw
material for the synthesis of the cryptocarya acetates.18 Therefore
the R. arrhizus mediated scale-up bioreduction of substrate 6 was
carried out and furnished (S)-t-Butyl-3-hydroxybutanoate 6a in
80.3% and with >99% enantiomeric purity.
O
O
4
5
O
O
N
O
O
6
7
The synthesis of (S)-(+)-
interest due to its analgesic and anticonvalsant activities.19 The R.
arrhizus mediated scale-up bioreduction of substrate was
reduced to the corresponding (S)-carbinol 7a in 71.3% yield and
with 78.3% enantiomeric purity.
a-phenyl-2-pyridylmethanol is of great
Chart 1. Prochiral ketones 1–7.
7
Table 1
Asymmetric reduction of various prochiral ketones using Rhizopus arrhizus
Substrate Product alcohol
% yielda % eeb
Confi.c
83.4 (S)
91.7 (S)
>99 (S)
96.4 (S)
97.1 (R)
3. Conclusion
1
2
3
4
5
6
7
1a, (S)-1-Phenylethanol
76
2a, (S)-1-(benzofuran-2-yl) ethanol
3a, (S)-6-Fluorochroman-4-ol
4a, (S)-4-phenyl-2-butanol
5a, (R)-1-phenyl-2-butanol
6a, (S)-t-butyl-3-hydroxybutanoate
99.3
95.4
92.8
79.8
80.3
71.3
We have explored the utility of fungus Rhizopus arrhizus (wild
type) for the synthesis of chiral carbinols with high enantioselec-
tivity and in quantitative yields. This effective and eco-friendly
protocol was found to be a versatile and promising tool for the
scale-up clean synthesis of chiral carbinols.
>99
(S)
7a, (S)-
a
-phenyl-2-pyridylmethanol
78.3 (S)
a
b
c
Isolated yield.
Determined by 1H NMR analysis of corresponding MTPA esters.
Assigned on the basis of the comparison of the rotation sign with the literature
4. Experimental
4.1. General
data.
Benzofuran carbinols are important units for the synthesis of
various types of biologically active molecules, such as bufuralols,
potent non-selective b-blockers antagonists.5 1-(Benzofuran-2-yl)-
carbinols exhibit various biological activities and its derivatives
were investigated as antibacterial or antifungal agents.6,7 Baker’s
yeast reduction of 2-acetylbenzo[b]furan gave (S)-1-(benzofuran-
2-yl)ethanol with moderate enantiomeric purity (55%) and in
moderate yield (60%),8 whereas kinetic resolution of racemic
1-(benzofuran-2-yl) ethanol yielded 49% of (S)-1-(Benzofuran-2-
yl) ethanol with 98.6% enantiomeric purity.9 Meanwhile, the
R. arrhizus mediated scale-up reduction of 2 furnished 99.3%
(S)-1-(benzofuran-2-yl)ethanol, 2a with 91.7% enantiomeric purity.
Chroman is the structural core of many natural products, such
as tocopherols, flavonoids, iso- and neoflavanoids, with anti-oxida-
tive activity.10 The 4-hydroxylated chroman was found in a num-
ber of natural products.11 The synthesis of scalable and highly
enantioselective chroman-4-amines is important since they are
used as core scaffolds in drug discovery programs. The enantiose-
lective ketone reduction to chiral chroman-4-ol followed by amine
inversion would also yield chiral chroman-4-amines.12 In this
All substrates (Aldrich, Fluka and Lancanster) were used as
received. Fungus R. arrhizus was obtained from the National Collec-
tion of Industrial Microorganisms, National Chemical Laboratory,
Pune, India. Fungus from PDA slant was cultivated on 150 ml ster-
ilized modified Czepak Dox medium in 500 ml Erlenmeyer flasks at
room temperature under static condition.
The IR spectra were scanned as films on Jasco model A-202 FT-
IR spectrometer. The 1H NMR spectra were recorded in CDCl3 with
a Bruker AC-200 spectrometer (200 MHz) and Varian 500 MHz.
Optical rotations were recorded with a Jasco DIP 360 digital
polarimeter.
4.2. General procedure for microbial reduction
In a cotton plugged 500 ml Erlenmeyer flask containing the 72 h
grown Rhizopus culture (150 ml sterilized medium), substrate 1
(100 mg) was added and incubated on a rotary shaker (100 rpm)
at room temperature for the desired period. The substrate and
organism controls were also run simultaneously. At the end of
Please cite this article in press as: Salvi, N. A. ; Chattopadhyay, S. Tetrahedron: Asymmetry (2016), http://dx.doi.org/10.1016/j.
tetasy.2016.01.008

4
N. A. Salvi, S. Chattopadhyay / Tetrahedron: Asymmetry xxx (2016) xxx–xxx
incubation, the mycelial mass was removed, washed with water,
and squeezed. The aqueous washings were combined with the
aqueous filtrate and extracted with CHCl3 (3 Â 50 ml). The organic
extract was washed with water, dried, and concentrated to obtain a
residue. This was subjected to preparative TLC (silica gel, 10%
EtOAc/Pet. Ether, visualization by UV exposure) to furnish the
respective product alcohol 1a. The spectroscopic and chiroptical
data of the product alcohols were matched with reported literature
data. The enantiomeric purity was determined by 1H NMR of the
corresponding MTPA esters.20
4.7.1. Scale-up bioreduction of 1–7
The laboratory scale-up bioreduction of ketones 1–7 was car-
ried out as follows. After 72 h of fermentation, R. arrhizus mycelia
were separated from the culture broth. The 10% wet mycelia were
put in a 1.5 L sterilized fresh culture medium as working volume in
5 L Erlenmeyer flask under aseptic conditions and incubated at
room temperature for 72 h under static conditions. After the
growth of the fungus, the substrate (1 g) in ethanol was added
directly to the medium and then incubated at room temperature
on a rotary shaker (100 rpm) for 8 days. At the end of the incuba-
tion period, the mycelia were separated by filtration. Mycelia
was washed with water and then the combined aqueous medium
was extracted with chloroform. The chloroform extract washed
with water and dried over Na2SO4. After removal of the solvent
under reduced pressure, the product alcohol was isolated, purified,
and characterized as described earlier. The absolute configuration
was determined by the sign of the specific rotation and comparison
with the literature data.
4.3. General procedure for preparation of the MTPA esters
A mixture of (R)-MTPA (25 mg) and SOCl2 (0.250 ml) in toluene
(2 ml) was refluxed for 3 h. After removing the excess SOCl2 in vac-
uum, the resultant MTPA chloride was taken in CH2Cl2 (0.5 mL) and
added to a solution of the alcohol (15 mg), pyridine (0.1 ml), and
4,4-dimethylaminopyridine (1–2 crystals) in CH2Cl2 (0.250 mL).
After stirring the mixture for 16 h at room temperature, the excess
pyridine was removed by purging with N2 gas, and the residue was
subjected to preparative thin-layer chromatography (silica gel, 10%
EtOAc/hexane) to isolate the respective MTPA esters. 1H NMR anal-
yses were carried out with the pure samples.
4.8. Spectroscopic characterization of substrates
4.8.1. (S)-1-Phenylethanol 1a
Isolated yield: 0.77 g, [
a]
23 = À45.9 (c 0.974, CHCl3), 83.4% ee
D
{lit.2d
[
a]
23 = À43.7 (c 0.90, CHCl3) 68% ee}; 1H NMR (CDCl3,
D
4.4. Growth conditions of Rhizopus arrhizus for bioreduction
200 MHz): d 1.52 (d, 3H, CH3), 2.99 (bs, 1H, OH), 4.87 (q, 1H,
CHOH), 7.42–7.28 (5H, Ar); 13C NMR (CDCl3, 200 MHz, ppm):
24.29, 69.86, 125.23, 127.04, 128.15, 145.71; methoxyl
resonances of MTPA ester, 1H NMR: d 3.56 [major, (S)-isomer]
and 3.48 [minor, (R)-isomer].
4.4.1. Bioreduction with growing culture
In this process, substrate 1 and the inoculum were added simul-
taneously to the sterile medium and the organism was allowed to
grow for different incubation periods on a rotary shaker.
4.8.2. (S)-1-(Benzofuran-2-yl) ethanol 2a
4.4.2. Bioreduction with grown culture
Isolated yield: 1.0 g, [
a
]
D
26 = À16.6 (c 0.728, CHCl3), 91.7% ee
In this process, substrate 1 was added to pre-cultured aqueous
medium containing 72 h grown organism and incubated at room
temperature for different incubation periods on a rotary shaker.
{lit.9 = À16.6 (c 1.0, CHCl3), 98.6% ee}; 1H NMR (CDCl3, 200 MHz):
d 1.62 (d, 3H, CH3), 2.80 (s, 1H, OH), 4.99 (q, 1H, CHOH), 6.58
(s,1H, benzofuran CH), 7.31–7.21 (m, 2H, Ar), 7.56–7.45 (m, 2H,
Ar); 13C NMR (CDCl3, 200 MHz, ppm): 21.37, 64.13, 101.75,
111.75, 121.03, 122.73, 124.13, 128.09, 154.73, 160.17; methoxyl
resonances of MTPA ester, 1H NMR: d 3.58 [major, (S)-isomer]
and 3.53 [minor, (R)-isomer].
4.4.3. Bioreduction with resting cells
Resting cells are non-growing, living cells with retention of
most of the enzyme activities of growing cells. They are obtained
by harvesting 72 h grown culture by filtering the culture from
medium and re-suspended in sterile water (100 ml). The bio-trans-
formation was performed in the second step by adding substrate 1,
for various periods at room temperature on rotary shaker.
4.8.3. (S)-6-Fluorochroman-4-ol 3a
Isolated yield: 0.95 g, [
a
]
24 = À48.4 (c 0.320, CHCl3), >99% ee; 1H
D
NMR (CDCl3, 200 MHz): d 1.43 (s, 1H, OH), 1.89–2.17 (m, 2H, CH2),
4.16–4.22 (m, 2H, CH2), 4.71 (t, 1H, CHOH), 6.72–7.25 (m, 3H, Ar.);
13C NMR (CDCl3, 200 MHz, ppm): 30.84, 62.18, 63.29, 114.90,
115.35, 116.36,116.82, 117.99, 118.15, 150.54, 154.40; methoxyl
resonances of MTPA ester, 1H NMR: d 3.52 [major, (S)-isomer].
4.5. Effect of substrate concentration on bioreduction
The effect of acetophenone concentrations ranging from 50 to
500 mg/flask, on bioreduction was studied with 72 h grown culture
for 8 days of incubation period.
4.8.4. (S)-4-Phenyl-2-butanol 4a
Isolated yield: 0.94 g, [a]
25 = +16.5 (c 0.569, CHCl3), 96.4% ee
D
4.6. Effect of by organic solvent vehicles
{lit.2i = +15.3 (c 3.32, CHCl3), >93% ee}; 1H NMR (CDCl3,
200 MHz): d 1.25 (d, 3H, CH3), 1.74–1.86 (m, 2H, CH2), 2.16 (s,
1H, OH), 2.66–2.80 (m, 2H, CH2), 3.87 (m, 1H, CHOH), 7.18–7.36
(m, 5H, Ar.); 13C NMR (CDCl3, 200 MHz, ppm): 23.31, 31.95,
40.64, 67.10, 125.59, 128.19, 128.22, 141.98; methoxyl
resonances of MTPA ester, 1H NMR: d 3.62 [major, (S)-isomer]
and 3.59 [minor, (R)-isomer].
The availability of the substrate to the active site of the enzyme
is generally carried out by dissolving the compound in a suitable
solvent of low toxicity to the biocatalyst. For this, various water
miscible and water immiscible organic solvents were used as sol-
vent vehicles to dissolve acetophenone (100 mg/ml) and their
effect on the yield and the enantiomeric purity of the product alco-
hols were studied using 72 h grown culture for 8 days of incuba-
tion period at room temperature on a rotary shaker (100 rpm).
4.8.5. (R)-1-Phenyl-2-butanol 5a
Isolated yield: 0.81 g, [
a
]
24 = À28.7 (c 0.436, CHCl3) 97.1% ee
D
{lit.2i = À31.1 (c 2.82, CHCl3), 94.9% ee}; 1H NMR (CDCl3,
200 MHz): d 1.05 (t, 3H, CH3), 1.52–1.77 (m, 2H, CH2), 1.80
(s, 1H, OH), 2.93 (m, 2H, CH2), 3.76–3.83 (m, 1H, CHOH),
7.24–7.42 (m, 5H, Ar); 13C NMR (CDCl3, 200 MHz, ppm): 9.91,
29.34, 43.41, 73.82, 126.16, 128.30, 129.29, 138.63; methoxyl
4.7. Effect of temperature on the bioreduction
The bioreduction of 1 was carried out at 24–48 °C temperature
range using 72 h grown R. arrhizus culture for 8 days of incubation
period on a rotary shaker (100 rpm).
Please cite this article in press as: Salvi, N. A. ; Chattopadhyay, S. Tetrahedron: Asymmetry (2016), http://dx.doi.org/10.1016/j.
tetasy.2016.01.008

N. A. Salvi, S. Chattopadhyay / Tetrahedron: Asymmetry xxx (2016) xxx–xxx
5
resonances of MTPA ester, 1H NMR: d 3.46 [minor, (S)-isomer] and
3.43 [major, (R)-isomer].
2006, 14, 4918–4922; (h) Salvi, N. A.; Chhattopadhyay, S. Tetrahedron:
Asymmetry 2008, 19, 1992–1997; (i) Salvi, N. A.; Chattopadhyay, S.
Tetrahedron: Asymmetry 2011, 22, 1512–1515.
3. Stereoselective Synthesis of Chiral Compounds Using Whole-cell Bio-catalysts,
Chapter 14. In Stereoselective Biocataly-sis, Patel, R.N., Ed.; Marcel Decker: New
York, 2000; p 366.
4. (a) Martin, C. K. A.; Perlman, D. Biotechnol. Bioeng. 1975, 17, 1473–1483; (b)
Mizrahi, A.; Miller, G. J. Bacteriol. 1969, 97, 1155–1159.
5. Machin, P. J.; Hurst, D. N.; Osbond, J. M. J. Med. Chem. 1985, 28, 1648–1651.
6. Bevinakatti, H. S.; Badiger, V. V. Arch. Pharm. (Wein-heim) 1981, 314, 162–167.
7. Wahbi, Y.; Caujolle, R.; Tournaire, C.; Payard, M.; Linas, M. D.; Seguela, J. P. Eur.
J. Med. Chem. Chim. Ther. 1995, 30, 955–962.
8. Paizs, C.; Tosa, M.; Majdik, C.; Moldovan, P.; Novak, L.; Kolonits, P.; Marcovici,
A.; Irimie, F.-D.; Poppe, L. Tetrahedron: Asymmetry 2003, 14, 1494–1501.
9. Paizs, C.; Toșa, M.; Bo´ dai, V.; Szaka´cs, G.;´Kmecz, I.; Sima´ndi, B.; Majdik, C.;
Nova´k, L.; Irimie, F.-D.;´Poppe, L. Tetrahedron: Asymmetry 2003, 14, 1943–1949.
10. (a) Pietta, P. G. J. Nat. Prod. 2000, 63, 1035–1042; (b) Nijveldt, R. J.; van Nood, E.;
van Hoorn, D. E. C.; Boelens, P. G.; van Norren, K.; van Leeuwen, P. A. M. Am. J.
Clin. Nutr. 2001, 74, 418–425.
11. Saengchantara, S. T.; Wallace, T. W. Nat. Prod. Rep. 1986, 465–475.
12. Lloyd, J.; Atwal, K. S.; Finlay, H. J.; Nyman, M.; Huynh, T.; Bhandaru, R.; Kover,
A.; Schmidt, J.; Vaccaro, W.; Conder, M. L.; Jenkins-West, T.; Levesque, P. Bioorg.
Med. Chem. Lett. 2007, 17, 3271–3275.
13. Carlsen, P. H. J.; Katsuki, T.; Martin, V. S.; Sharpless, K. B. J. Org. Chem. 1981, 46,
3936–3938.
14. (a) Mori, K. Tetrahedron 1975, 31, 3011–3012; (b) Seebach, D.; Rogga, S.;
Zimmermann, J. Biological-Chemical Preparation of 3-Hydroxycarboxylic Acids
and their Use in EPC-Syntheses in Stereochemistry of Organic and Bioorganic
Transformations, Workshop Conferences Hoechst, Bartmann, W.; Sharpless, K. B.,
Eds.; Verlag Chemie, Weinheim, 1987; Vol. 17, pp 85–126.; (c) White, J. D.;
Amedio, J. C. J. Org. Chem. 1989, 54, 736–738.
4.8.6. (S)-t-Butyl-3-hydroxybutanoate 6a
Isolated yield: 0.81 g, [a]
26 = +28.6 (c 0.483, CHCl3) >99% ee
D
{lit.2f = +32.3 (c 1.03, CHCl3), 99.0% ee}; 1H NMR (CDCl3,
200 MHz): d 1.25 (d, 3H, CH3), 1.48 (s, 9H, CH3), 2.27–2.49 (m,
2H, CH2), 3.09 (s, 1H, OH),, 4.08–4.22 (m, 1H, CHOH); 13C NMR
(CDCl3, 200 MHz, ppm): 22.21, 27.93, 43.79, 64.18, 80.94, 172.15;
methoxyl resonances of MTPA ester, 1H NMR: d 3.55 [major,
(S)-isomer].
4.8.7. (S)-
a
-Phenyl-2-pyridylmethanol 7a
Isolated yield: 0.72 g, [
a]
D
25 = +120.9 (c 0.492, CHCl3) 78.3% ee
{lit.2c = +106.1 (c 1.684, CHCl3), 82.0% ee} 1H NMR (CDCl3,
200 MHz): d 5.04 (s, 1H, OH), 5.82 (s, 1H, CHOH), 7.19–7.46 (m,
7H, Ar.), 7.61–7.69 (m, 1H, Ar), 8.60 (1H Ar); 13C NMR (CDCl3,
200 MHz, ppm): 74.95, 121.31, 122.38, 127.02, 127.78, 128.53,
136.80, 143.17, 147.78, 160.84; methoxyl resonances of MTPA
ester, 1H NMR: d 3.53 [major, (S)-isomer] and 3.57 [minor,
(R)-isomer].
References
15. Liese, A.; Seelbach, K.; Wandry, C. Industrial Biotransformations; Wiley-VCH:
New York, 2000. p 423.
16. Drewes, S. E.; Sehlapelo, B. M.; Horn, M. M.; Scott-Shaw, R.; Sandor, P.
Pytochemistry 1995, 38, 1427–1430.
17. Sam, T. W.; Yeu, C. S.; Jodynis-Liebert, J.; Murias, M.; Bloszyk, E. Planta Med.
2000, 66, 199–205.
18. Yadav, J. S.; Purushothama Rao, P.; Sridhar Reddy, M.; Venkateswar Rao, N.;
Prasad, A. R. Tetrahedron Lett. 2007, 48, 1469–1471.
1. (a) Mandal, D.; Ahmad, A.; Khan, M. I.; Kumar, R. J. Mol. Catal. B: Enzym. 2004,
27, 61–63; (b) Faber, K. Biocatalytic Application. In Biotransformations in
Organic Chemistry; Springer, 2000; pp 192–193.
2. (a) Salvi, N. A.; Patil, P. N.; Udupa, S. R.; Banerji, A. Tetrahedron: Asymmetry
1995, 6, 2287–2290; (b) Salvi, N. A.; Rane, S. S.; Udupa, S. R. Biotechnol. Lett.
1995, 17, 285–290; (c) Salvi, N. A.; Udupa, S. R.; Banerji, A. Biotechnol. Lett. 1998,
20, 201–203; (d) Salvi, N. A.; Chhattopadhyay, S. Tetrahedron 2001, 57, 2833–
2839; (e) Salvi, N. A.; Badheka, L. P.; Chhattopadhyay, S. Biotechnol. Lett. 2003,
25, 1081–1086; (f) Salvi, N. A.; Chhattopadhyay, S. Tetrahedron: Asymmetry
2004, 15, 3397–3400; (g) Salvi, N. A.; Chhattopadhyay, S. Bioorg. Med. Chem.
19. Frank, E.; Gearien, J.; Megahy, M.; Pokorny, C. J. Med. Chem. 1971, 14, 551–553.
20. Dale, J. A.; Mosher, H. S. J. Am. Chem. Soc. 1973, 95, 512–5192.
Please cite this article in press as: Salvi, N. A. ; Chattopadhyay, S. Tetrahedron: Asymmetry (2016), http://dx.doi.org/10.1016/j.
tetasy.2016.01.008