A convenient stereoselective synthesis of 5-hydroxy-3-oxoesters and 3-hydroxy-5-oxoesters

Article abstract of DOI:10.1016/j.tetasy.2017.05.005

A biocatalytic approach was employed for the asymmetric reduction of sterically demanding ketones to prepare 3-hydroxy-5-oxo-5-phenylpentanoates and 5-hydroxy-3-oxo-5-phenylpentanoates. Screening a collection of microorganisms led to the identification of

Full text of DOI:10.1016/j.tetasy.2017.05.005

Tetrahedron: Asymmetry xxx (2017) xxx–xxx
Contents lists available at ScienceDirect
Tetrahedron: Asymmetry
journal homepage: www.elsevier.com/locate/tetasy
A convenient stereoselective synthesis of 5-hydroxy-3-oxoesters and
3-hydroxy-5-oxoesters
a
b
b
a
_
Anna Za˛dło-Dobrowolska , Joerg H. Schrittwieser , Barbara Grischek , Dominik Koszelewski ,
Wolfgang Kroutil b, , Ryszard Ostaszewski a,
⇑
⇑
a Institute of Organic Chemistry, Polish Academy of Sciences, Kasprzaka 44/52, 01-224 Warsaw, Poland
b Institute of Chemistry, University of Graz, NAWI Graz, BioTechMed Graz, Heinrichstrasse 28, 8010 Graz, Austria
a r t i c l e i n f o
a b s t r a c t
Article history:
A biocatalytic approach was employed for the asymmetric reduction of sterically demanding ketones to
prepare 3-hydroxy-5-oxo-5-phenylpentanoates and 5-hydroxy-3-oxo-5-phenylpentanoates. Screening a
collection of microorganisms led to the identification of stereocomplementary microbial strains that pro-
vide access to both enantiomers of 3-hydroxy-5-oxo-5-phenylpentanoates and 5-hydroxy-3-oxo-5-
phenylpentanoates with high enantiomeric excess (up to 99% ee). Moreover, the application of
Saccharomyces cerevisiae gave two diastereomers of 3,5-dihydroxy-5-phenylpentanoates with high
enantiomeric excess (up to 99% ee). The applicability of the identified strains was demonstrated by trans-
forming the obtained dihydroxy ester into the chemically valuable lactone (4S,6R)-tetrahydro-4-
hydroxy-6-phenyl-pyran-2-one.
Received 12 March 2017
Revised 4 May 2017
Accepted 8 May 2017
Available online xxxx
Ó 2017 Elsevier Ltd. All rights reserved.
1. Introduction
dynamic kinetic resolution.11 Although these methods were exten-
sively investigated, they failed to deliver ideal chemo- and
A key interest in organic chemistry is the stereoselective syn-
thesis of chiral building blocks.1 Among these, 3,5-dioxygenated
ester/amide motifs are of high interest, because they are found in
many biologically active compounds, such as the anti-cancer drugs
Ixempra and Berkeleyamide A (caspase-1 inhibitor),2 shown in
Scheme 1. Accordingly, various approaches have been devised to
synthesize these important substructures. For instance, regio-
and enantioselective reduction catalyzed by ketoreductases3 or
whole cell systems4 were extensively used for preparing 3,5-dihy-
droxy acid derivatives. Moreover, several chemical and biochemi-
cal approaches have been devised for the synthesis of optically
active 5-hydroxy-3-oxoesters and 3-hydroxy-5-oxoesters, includ-
ing asymmetric aldol-type reactions,5 additions of diketenes to
aldehydes promoted by chiral Schiff base-titanium alkoxide com-
plexes,6 dithiane anion chemistry,7 or Ru-catalyzed hydrogenation
of 3,5-diketoacid derivatives.8 In recent years, effective enzymatic
reductions applying ketoreductases have been developed.9
Although all stereoisomers were obtained, the reductions were
performed on sterically less demanding 3,5-dioxohexanoates.
Alternative protocols relied on enzymatic kinetic resolution10 and
stereoselectivity.
Furthermore, enantiopure 5-hydroxy-3-oxoesters and 3-
hydroxy-5-oxoesters are potential precursors to the tetrahydro-
2H-pyranone ring as shown in numerous reports (Scheme 2).12
The stereocontrolled construction is essential for the biological
activity of many pharmaceuticals.13 For instance, the antitumor
polyketide (+)-discodermolide contains the (4S,6R)-4-hydroxy-6-
phenyl-d-lactone subunit while lovastatin contains a (4R,6S)-4-
hydroxy-6-phenyl-d-lactone subunit. The recently discovered
diospongins A and B, isolated from the rhizomes of Dioscorea spon-
giosa exhibit promising inhibitory activities on bone resorption and
have potential application for the treatment of osteoporosis.14 In
particular, diospongins can be obtained via a diastereoselective
reduction of enantiomerically pure ethyl 3-hydroxy-5-phenyl-5-
oxopentanoate followed by cyclization.15 The target lactone can
also be provided from enantioselective lactonization of syn-3,5-
dihydroxy esters16 or anti-3,5-dihydroxy esters.17 Up to now, the
regio- and enantioselective synthesis of these compounds remains
challenging.
Previously we reported the results of screening a microbial cul-
ture collection, which led to the identification of stereocomple-
mentary whole-cell catalysts for the preparation of ethyl 3-
hydroxy-5-phenylpentanoate.18 Herein, we report the selective
reduction of sterically demanding 3,5-dioxo-5-phenylpentanoates.
⇑
Corresponding authors.
E-mail addresses: wolfgang.kroutil@uni-graz.at (W. Kroutil), r.ostaszewski@icho.
edu.pl (R. Ostaszewski).
http://dx.doi.org/10.1016/j.tetasy.2017.05.005
0957-4166/Ó 2017 Elsevier Ltd. All rights reserved.
_
Please cite this article in press as: Za˛dło-Dobrowolska, A. ; et al. Tetrahedron: Asymmetry (2017), http://dx.doi.org/10.1016/j.
tetasy.2017.05.005

_
2
A. Za˛dło-Dobrowolska et al. / Tetrahedron: Asymmetry xxx (2017) xxx–xxx
Careful selection of the microorganism enabled us to control the
chemo-, regio- and stereoselective reduction of a single keto group
either at the C3 or C5 position. Subsequent cyclization gave access
to (4S,6R)-tetrahydro-4-hydroxy-6-phenyl-pyran-2-one with high
enantiomeric purity.
2. Results and discussion
Identifying appropriate microorganisms possessing the enan-
tio- and diastereocomplementary selectivity for the reduction of
diketoester 1 may allow us to prepare each of the four possible
diastereomeric products
4
with high enantiomeric and
diastereomeric purities. However, diketoester 1 may also be
asymmetrically reduced at only one carbonyl group generating
multi-functionalized compounds 2 or 3 (Scheme 2).
O
S
Initially, an in-house culture collection of 250 microorganisms
was screened for the reduction of compound 1a using freeze-dried
cells. Glucose dehydrogenase (GDH) and 2-propanol were used for
cofactor regeneration, as well as 2-propanol to improve the solubil-
ity of the substrate.19 Since the cofactor preference of the involved
enzymes was not known, both NADH as well as NADPH were
added. Probably due to the sterically hindered carbonyl groups,
compound 1a was accepted only by three microorganisms. These
three biocatalysts, Arthrobacter sp. DSM 7325 Pseudomonas sp.
DSM 6978 and Actinomyces sp. SRB-AN053 FCC 027, were selected
for experiments on a preparative scale (Table 1).
OH
N
NH
HN
O
O
OH
O
OH
O
(-)-Berkeleyamide A
Ixempra
HO
O
O
O
O
H
Thus, 236 mg (1 mmol) of diketo ester 1a were subjected to a
biotransformation, which reached completion within 72 h at
30 °C. Two main products, namely 2a and 3a were identified
(Scheme 2). Out of the tested biocatalysts, Arthrobacter sp. trans-
formed diketoester 1a into a mixture of two products, (R)-config-
ured 2a (49% ee, Table 1, entry 1) and (S)-configured 3a (96% ee).
The separation of these products by column chromatography was
not feasible. Thus, Arthrobacter sp. allowed to reduce both keto
O
O
OH
H3C
(-)-diospongin B
lovastatin
Scheme 1. Bioactive compounds.
O
O
O
OR
1a R=Et
1b
R=t-Bu
Whole cell catalyst
Tris-HCl buffer (pH 7.5)
O
OH
O
OH
O
O
OR
OR
3a R=Et
3b
2a R=Et
2b
NaBH4, B(OMe)Et2
dry THF, -10 C
R=t-Bu
R=t-Bu
OH
OH
O
OR
4a
R=Et
4b R=t-Bu
p-TsOH
DCM, rt
OH
O
O
5
Scheme 2. Synthesis of (4R,6S)-tetrahydro-4-hydroxy-6-phenylpyran-2-one.
_
Please cite this article in press as: Za˛dło-Dobrowolska, A. ; et al. Tetrahedron: Asymmetry (2017), http://dx.doi.org/10.1016/j.
tetasy.2017.05.005

_
A. Za˛dło-Dobrowolska et al. / Tetrahedron: Asymmetry xxx (2017) xxx–xxx
3
Table 1
Reduction of ethyl 3,5-dioxo-5-phenylpentanoate 1a employing freeze-dried microorganismsa
Entry
Microorganism
NAD+
NADP+
GDH/glucose
Yield 2a (%)
ee (%)
Yield 3a
ee (%)
(%)
1
2
3
4
5
6
7
Arthrobacter sp.
Arthrobacter sp.
Arthrobacter sp.
Pseudomonas sp.
Pseudomonas sp.
Pseudomonas sp.
Saccharomyces cerevisiae
+
+
+
+
36
34
27
16
17
20
17
49 (R)
59 (R)
55 (R)
94 (S)
>99 (S)
78 (S)
23 (S)
29
22
18
<1
<1
<1
<1
96 (S)
71 (S)
66 (S)
nd
nd
nd
+
+
+
+
+
+
+
nd
a
Conditions: 30 °C, 120 rpm in a thermoshaker for 72 h, 2 g of lyophilized whole-cell biocatalyst in 100 mL of reaction solution, containing 20 mM glucose, glucose
dehydrogenase (1 mg mLÀ1), 0.5 mM NADH or/and 0.5 mM NADPH, 1 mmol substrate in a mixture of buffer (100 mM Tris-HCl pH 7.5) and 2-propanol (90:10, v/v). Yield
refers to isolated product 2a and 3a after column chromatography. The ees of 2a and 3a were determined by HPLC equipped with a Chiralcel OB-H column.
functionalities. In contrast, Pseudomonas sp. reduced the diketone
in a regio- and enantioselective fashion transforming only the keto
moiety at the b-position to (S)-2a with high enantiomeric excess
(94% ee, Table 1, entry 4). It is worth noting that the Pseudomonas
sp. gave access to the (S)-enantiomer of 2a while Arthrobacter sp.
provided the (R)-enantiomer. Actinomyces sp. gave only trace
amounts of the product on a millimolar scale. Optimization of
the cofactors led to enantiomerically pure 3-hydroxy-5-keto ester
(S)-2a (>99% ee, Table 1, entry 5), a useful chiral synthon and build-
ing block, which is difficult to synthesize otherwise. An additional
experiment with Yeast from Saccharomyces cerevisiae, which is
known for its versatility, led to (S)-2a with low yield and low enan-
tiomeric excess (Table 1, entry 7).
Due to the presence of various types of enzymes in whole-cell
catalysts, conversions were very high (>85%), while the isolated
product yields were quite low (16–36%). Whole-cell catalysts con-
tain besides dehydrogenases also hydrolases, and since all investi-
gated compounds 1a–4a possess an ester functional group, they
are susceptible to enzymatic hydrolysis. For this reason, the ethyl
ester group was replaced by the sterically demanding t-butyl ester,
which is less susceptible to hydrolysis.
Employing t-butyl 3,5-dioxo-5-phenylpentanoate 1b as the
substrate resulted in higher product yields (up to 40%) as well as
lower conversions. The latter is most likely due to the even more
bulky substrate. Arthrobacter sp. catalyzed the reduction of
substrate 1b exclusively at the d-carbonyl group to afford the
(R)-enantiomer of 3b as the only product (Table 2, entries 1–3).
Thus, by changing the ester moiety, the regioselectivity of the bio-
catalyst could be controlled. Additionally, the t-butyl group led to a
switch of stereopreference compared to the ethyl ester 1a. The
reduction of 1b catalyzed by Pseudomonas sp. took place again
preferentially at the b-carbonyl group to afford the (R)-configured
2b, which also corresponded to a switch in stereoselectivity
compared to the reduction of the ethyl ester. Independent of the
cofactor added, high ee values were obtained (92–96% ee, Table 2,
entries 4–6). For this substrate Actinomyces sp. proved to be stere-
ocomplementary to Pseudomonas sp. leading to (S)-configured 2b
with 62% ee (Table 2, entry 9). In all cases, the determined conver-
sions were independent of the presence or absence of glucose and
GDH. The developed method is a convenient synthetic pathway to
obtain both enantiomers of 3-hydroxy-5-oxo-5-phenylpentanoic
esters. According to the literature, such compounds may be chem-
ically reduced in
a highly diastereoselective manner to all
diastereoisomers of 3,5-dihydroxy-5-phenylpentanoates and then
cyclized to a desired lactone.12
As an alternative, racemic 3a was reduced with the whole-cell
catalysts at the b-carbonyl group, which may lead to the formation
of four stereoisomers of dihydroxyester 4 (Scheme 2). The isolation
of syn-(3S,5R) might be very valuable in the synthetic pathway
leading to desired lactone (4S,6R)-tetrahydro-4-hydroxy-6-
phenyl-pyran-2-one. Whole cells of Saccharomyces cerevisiae were
selected as the biocatalyst. Cells were shaken under fermenting
and non-fermenting conditions in water at room temperature for
24 h. An inexpensive carbon source (glucose) was added for the
internal cofactor regeneration in the metabolism of the cells.
Unreacted substrate and the obtained products were isolated and
analyzed (Table 3).
The addition of glucose was found to accelerate the yeast-medi-
ated reduction from 38% to 66% product yield (Table 3, entries 1 vs
2). Based on the sign of the specific rotation of the unreacted
substrate, it was noticed that yeast transformed preferentially
the (R)-configured substrate, while the (S)-enantiomer was recov-
ered.10 5-Hydroxy-3-oxoester 3a was reduced by yeast to give the
corresponding syn-product (3S,5R)-4 and anti-product (3S,5S)-4
with good enantiomeric excess (Table 3, entry 2). Only 60–80% of
the recovered substrate and product were isolated because of
Table 2
Reduction of t-butyl 3,5-dioxo-5-phenylpentanoate 1b with whole-cell biocatalysts
Entry
Microorganism
NADH
NADPH
+
GDH/glucose
+
Yield 2b (%)
ee 2b (%)
Yield 3b (%)
ee 3b (%)
1
2
3
4
5
6
7
8
9
10
Arthrobacter sp.
Arthrobacter sp.
Arthrobacter sp.
Pseudomonas sp.
Pseudomonas sp.
Pseudomonas sp.
Actinomyces sp.
Actinomyces sp.
Actinomyces sp.
Saccharomyces cerevisiae
+
+
<1
<1
<1
27
27
25
40
36
40
<1
nd
nd
nd
92 (R)
96 (R)
93 (R)
34 (S)
52 (S)
62 (S)
nd
34
33
20
<1
<1
<1
<1
<1
<1
<1
84 (R)
80 (R)
76 (R)
nd
nd
nd
nd
nd
nd
nd
+
+
+
+
+
+
+
+
+
+
+
+
Conditions: 30 °C, 120 rpm in a thermoshaker for 72 h, 2 g of lyophilized whole-cell biocatalyst in 100 mL of reaction solution, containing 20 mM glucose, glucose dehy-
drogenase (1 mg mLÀ1), 0.5 mM NADH or/and 0.5 mM NADPH, 1 mmol substrate in a mixture of buffer (100 mM Tris-HCl, pH 7.5) and 2-propanol (90:10, v/v). Yield refers to
isolated product 2b and 3b after column chromatography. The ee of 3a and 3b was determined by HPLC equipped with a Chiralcel OB-H or Chiralpak IA column; nd—non
defined.
_
Please cite this article in press as: Za˛dło-Dobrowolska, A. ; et al. Tetrahedron: Asymmetry (2017), http://dx.doi.org/10.1016/j.
tetasy.2017.05.005

_
4
A. Za˛dło-Dobrowolska et al. / Tetrahedron: Asymmetry xxx (2017) xxx–xxx
Table 3
Enzymatic reduction of racemic ethyl 5-hydroxy-5-phenyl-3-oxopentanoate 3a
Entry
Systema
Additives
Yield 4 (%)
dr (syn:anti)
eesyn
eeanti
Substrate 3a recovery (%)
ee 3a
1
2
3
4
5
6
7
8
9
A
B
B
B
B
B
B
B
B
None
None
38
66
45
52
40
54
65
59
57
77:23
74:26
78:22
78:22
76:24
75:25
56:44
60:40
60:40
88
83
83
75
78
80
94
79
98
>99
>99
91
99
98
96
98
98
>99
23
15
45
17
19
23
6
50
70
32
64
58
54
54
50
94
5% v/v hexane
5% v/v 2-propanol
5% v/v diethylether
5% v/v acetone
Allylbromideb
Allylalcoholb
Ethyl bromoacetateb
4
8
Conditions: asystem A—non-fermenting: Saccharomyces cerevisiae (10 g) was suspended in 100 mL of water. After stirring for 30 min, compound 3a (200 mg) dissolved in
4 mL of water or in organic solvent was added. The resulting cell suspension was shaken at room temperature for 24 h; system B—fermenting: 4 g glucose was added;
b100 mg of inhibitor was added. Yield refers to isolated product 4 after column chromatography. Substrate 3a recovery refers to isolated substrate 3a after column
chromatography. The ee of 3a, 4 and dr were determined by HPLC equipped with a Chiralcel OB-H column and by 1H NMR.
by-product formation. Possible explanations for this include the
hydrolysis of the ester moiety, oxidation of the hydroxyl group,
side reactions with the fermentation products, while the
product and starting material might be retained by lipids in the
whole cells.
According to the literature, the stereoselectivity and chemose-
lectivity can be tuned by the addition of organic solvents, immobi-
lization of biocatalysts or selective inhibition of one of the various
enzymes present in the microorganism.20 In order to investigate
the effect of organic solvent addition, reactions were performed
under fermenting conditions with 5% by volume of organic co-sol-
vent. Hexane, 2-propanol, diethyl ether and acetone led to slightly
reduced yields without a significant influence on the enzyme enan-
tioselectivity (Table 3, entries 3–6), hence none of them were used
in further optimization studies.
susceptible to side reactions such as hydrolysis. Despite these chal-
lenges, the developed method allowed us to obtain both enan-
tiomers of 5-hydroxy-5-phenyl-3-oxopentanoate
3
and 3-
hydroxy-5-phenyl-5-oxopentanoate with high enantiomeric
2
excess and two diastereoisomers of 3,5-dihydroxy-5-phenylpen-
tanoate 4 with excellent enantiomeric and diastereomeric purities.
The applicability of the developed method was demonstrated by
converting ethyl (3S,5R)-dihydroxy-5-phenylpentanoate into the
chemically valuable lactone (4S,6R)-tetrahydro-4-hydroxy-6-phe-
nyl-pyran-2-one.
4. Experimental
4.1. General
1H NMR and 13C NMR spectra were recorded in CDCl3 solution
on a Bruker 400 MHz Spectrometer. Chemical shifts are expressed
in parts per million values using TMS as an internal standard. Com-
mercial enzyme preparations were purchased from Sigma-Aldrich
and Novozymes. Wild-type whole-cell microorganisms are from
the collection of the Institute of Chemistry - Organic and Bioor-
ganic Chemistry, University of Graz. All chemicals were commer-
cial products of the analytical grade. Optical rotation
measurements were done on a Jasco P-2000 polarimeter. The HPLC
The stereochemical direction of the reduction reaction may be
controlled by the careful design of the substrate or by selective
inhibition of one of the involved dehydrogenases. Ethyl bromoac-
etate, allyl bromide and allyl alcohol were found to be suitable
inhibitors. When using ethyl bromoacetate (Table 3, entry 9), the
highest enantiomeric purity (94% ee) of the recovered substrate
and obtained products (3S,5R)-4 (98% ee) and (3S,5S)-4 (>99% ee)
were found. The product diastereoisomers were separated by col-
umn chromatography on silica gel. The absolute configuration of
the products was assigned based on the specific rotation measure-
ments and chemical correlation.10,12,15,21
analyses were performed with
a Varian ProStar instrument
equipped with chiral-phase columns (Chiralcel OB-H, Chiralpak
IA; Daicel, Japan). The mobile phase was a mixture of hexane and
2-propanol, the proportion of solvents and flow rate vary for differ-
ent compounds. TLC was done on silica gel 60 F254 aluminum
sheets (Merck). For more details see Supporting Information.
Finally, to show the applicability of the developed procedure,
(3S,5R)-4 (98% ee) was lactonized to the chemically valuable lac-
tone (4S,6R)-5 by using p-toluenesulfonic acid (See Supporting
Information).
The biocatalytic reduction may be developed into a convenient
synthetic pathway to obtain nonracemic 5-aryl-5-hydroxy-3-
oxopentanoates and 5-aryl-3-hydroxy-5-oxopentanoates. Such
compounds can be chemically reduced in a highly diastereoselec-
tive manner to 5-aryl-3,5-dihydroxypentanoates and then cyclized
to a synthetically valuable substituted tetrahydro-2H-pyranone
ring. Furthermore, two diastereoisomers (3S,5R)-4 and (3S,5S)-4
were obtained with high enantiomeric excess (>98% ee) by stereos-
elective reduction of racemic 3a using whole cells of Saccharomyces
cerevisiae.
4.2. Bioreduction with whole-cell biocatalysts
The whole cell biocatalyst (2 g) was suspended in 100 mL of
reaction solution, containing glucose dehydrogenase (1 mg mLÀ1),
20 mM glucose, 0.5 mM NAD+, 0.5 mM NADP+, 1 mmol substrate
1a or 1b in a mixture of buffer (100 mM Tris-HCl, pH 7.5) and 2-
propanol (90:10; v/v). Biotransformations were conducted at
30 °C and 120 rpm in a thermoshaker for 48 h. After this time,
the biocatalyst was removed by centrifugation and the reaction
mixture was extracted with ethyl acetate. The organic phase was
separated, dried (MgSO4), evaporated under reduced pressure
and the product was purified by column chromatography on silica
gel with hexane/ethyl acetate as an eluent.
3. Conclusion
Herein microbial catalysts for the stereoselective synthesis of
3,5-dihydroxyesters, 3-hydroxy-5-oxoesters and 5-hydroxy-3-
oxoesters were investigated. The set-up of the stereogenic centers
of the examined compounds is very demanding, due to the sterical
hindrance of the corresponding ketone, but is of high interest. Due
to the presence of the ester groups in these molecules, they are
4.3. Bioreduction with Saccharomyces cerevisiae
Saccharomyces cerevisiae (10 g) and sucrose (4 g) were sus-
pended in water (100 mL). After stirring for 30 min, ethyl
_
Please cite this article in press as: Za˛dło-Dobrowolska, A. ; et al. Tetrahedron: Asymmetry (2017), http://dx.doi.org/10.1016/j.
tetasy.2017.05.005

_
A. Za˛dło-Dobrowolska et al. / Tetrahedron: Asymmetry xxx (2017) xxx–xxx
5
5-hydroxy-5-phenyl-3-oxopentanoate 3b (200 mg) dissolved in
4 mL of organic solvent was added. The resulting cell suspension
was shaken at room temperature (21 °C) for 24 h. After this time,
the cells were centrifuged and the mixture was extracted with
ethyl acetate (3 Â 50 mL). The combined organic layers were dried
over MgSO4. The solvent was evaporated and the product was puri-
fied by column chromatography on silica gel using hexane/ethyl
acetate.
285.1103, found, 285.1100; Element. Anal. calcd for C15H18O4: C
68.68; H 6.92; found: C 68.70, 6.94.
4.9. t-Butyl 3-hydroxy-5-oxo-5-phenylpentanoate 2b
1H NMR (CDCl3, 400 MHz, ppm) d 7.90–7.87 (m, 2H, Ar), 7.53–
7.49 (m, 1H, Ar), 7.42–7.38 (m, 2H, Ar), 4.53 (quin, 1H, J = 5.2 Hz,
CH), 3.52 (br s, 1H, OH), 3.15–3.09 (m, 2H, CHCH2COO), 2.49–
2.46 (m, 2H, COCH2CH), 1.40 (s, 9H, 3ÂCH3); 13C NMR (CDCl3,
200 MHz, ppm)d 199.4, 171.4, 136.8, 133.5, 128.7, 128.1, 81.2,
64.9, 44.4, 41.9, 28.1; HR-MS (ESI, [M+H+] calcd for: C15H20O4Na,
4.4. Ethyl 3,5-dioxo-5-phenylpentanoate 1a
1H NMR (CDCl3, 400 MHz, ppm, enol:ketone = 92:8) d 15.77 (s,
0.9H, OH), 7.95–7.93 (d, 0.2H), 7.89–7.87 (d, 1.96H, Ar), 7.53–
7.43 (m, 3H, Ar), 6.29 (s, 1H, CH), 4.25–4.20 (m, 2H, OCH2CH3),
3.64 (s, 0.2H), 3.47 (s, 1.6H, CH2), 1.33–1.23 (m, 3H, OCH2CH3);
13C NMR (CDCl3, 100 MHz, ppm) d 189.2, 182.6, 167.5, 134.1,
132.6, 128.7, 127.1, 96.7, 61.5, 45.9, 14.1; HR-MS (ESI, [M+H+]
calcd for: C13H14O4Na, 257.0790, found, 257.0784; Element. Anal.
calcd. for C13H14O4: C, 66.66; H, 6.02; found: C, 66.52; H, 5.99.
287.1259, found, 287.1259; (R)-2b: [
responding to 93% ee determined by HPLC; (S)-2b: [
0.75, CHCl3) corresponding to 62% ee determined by HPLC.
a
]
D = +13.6 (c 0.28, CHCl3) cor-
a]
D = À8.8 (c
4.10. t-Butyl 5-hydroxy-3-oxo-5-phenylpentanoate 3b
1H NMR (CDCl3, 400 MHz, ppm) d 7.40–7.26 (m, 5H, Ar), 5.22–
5.19 (dd, 1H, J1 = 3.6 Hz, J2 = 9.2 Hz, CH), 4.41 (s, 2H, COH2CO),
3.14 (br s, 1H, OH), 3.04–2.90 (m, 2H, CHCH2CO), 1.49 (s, 9H,
3xCH3);13C NMR (CDCl3, 200 MHz, ppm)d 203.4, 166.1, 142.6,
128.6, 127.7, 125.6, 82.3, 69.8, 51.6, 51.2, 28.0; Element. Anal. calcd
for C15H20O4: C, 68.16; H, 7.63; found: C, 68.07, 7.68; HR-MS (ESI,
[M+H+] calcd. for: C15H20O4Na, 287.1259, found, 287.1256; (R)-3b:
4.5. Ethyl 3-hydroxy-5-oxo-5-phenylpentanoate 2a
1H NMR (CDCl3, 400 MHz, ppm) d 7.96–7.94 (m, 2H, Ar), 7.60–
7.56 (m, 1H, Ar), 7.48–7.44 (m, 1H, Ar), 4.65 (quin, 1H, J = 6.2 Hz,
CH), 4.20–4.15 (q, 2H, J = 7.2 Hz, OCH2CH3), 3.55 (br. s., 1H, OH),
3.23–3.21 (d, 2H, J = 5.6 Hz, CHCH2COO), 2.63–2.61 (d, 2H,
J = 6.4 Hz, COCH2CH), 1.29–1.25 (t, 3H, OCH2CH3); 13C NMR (CDCl3,
200 MHz, ppm)d 199.4, 171.9, 136.1, 133.6, 128.7, 128.1, 64.8, 60.7,
44.3, 40.9, 14.2; HR-MS (ESI, [M+H+] calcd for: C13H16O4Na,
[
a
]
D = À26.6 (c 1.15, CHCl3) corresponding to 80% ee determined by
HPLC.
4.11. t-Butyl 3,5-dihydroxy-5-phenylpentanoate 4b
259.0946, found, 259.0945; (S)-2a: [
a]
D = +17.5 (c 0.75, CHCl3) cor-
1H NMR (CDCl3, 400 MHz, ppm, dr 53:47) d 7.31–7.17 (m, 5H,
Ar), 4.97 (dd, 0.5H, J1 = 7.3 Hz, J2 = 3.9 Hz), 4.89 (dd, 0.5H,
J1 = 3.3 Hz, J2 = 9.7 Hz), 4.21–4.16 (m, 1H), 3.6 (br s, 2H, 2ÂOH),
responding to >99% ee determined by HPLC.
4.6. Ethyl 5-hydroxy-3-oxo-5-phenylpentanoate 3a
2.42–2.30 (m, 2H) 1.85–1.65 (m, 2H), 1.38 (m, 9H, 3ÂCH3);13
C
NMR (CDCl3, 200 MHz, ppm) d172.1, 144.3, 128.4, 128.4, 127.5,
127.5, 125.7, 125.6, 81.6, 74.4, 71.3, 68.8, 65.8, 44.9, 44.0, 42.5,
42.0, 28.1; HR-MS (ESI, [M+H+] calcd for: C15H22O4Na, 289.1416,
found, 289.1411.
1HNMR(CDCl3, 400 MHz,ppm)d7.37–7.34(m,4H,Ar),7.30–7.26
(m, 1H, Ar), 5.20–5.17 (dd, 1H, J1 = 3.6 Hz, J2 = 9.2 Hz, CH), 4.21–4.16
(q, J = 7.2 Hz, OCH2CH3), 3.47 (s, 2H, COCH2CO), 3.03–2.97 (dd,
J1 = 9.2 Hz, J2 = 17.2 Hz, CHCH2CO), 2.93–2.88 (dd, J1 = 3.2 Hz,
J2 = 17.2 Hz, CHCH2CO), 1.29–1.25 (t, 3H, OCH2CH3);13C NMR (CDCl3,
200 MHz, ppm) d 202.8, 166.8, 142.5, 128.5, 127.8, 125.6, 69.8, 61.5,
51.6, 49.9, 14.0; HR-MS (ESI, [M+H+] calcd. for: C13H16O4Na,
259.0946, found, 259.0945; Element. Anal. calcd for C13H16O4: C,
4.12. (4S,6R)-Tetrahydro-4-hydroxy-6-phenyl-pyran-2-one 5
1H NMR (CDCl3, 400 MHz, ppm) d 7.41–7.32 (m, 5H, Ar), 5.74
(dd, 1H, J1 = 3.2 Hz, J2 = 11.3 Hz, CH), 4.41 (m, 2H, COCH2CH), 2.86
(dd, J1 = 4.9 Hz, J2 = 17.5 Hz, 1H, CH), 2.73 (m, 1H, CH2), 2.21–2.01
(m, 3H); 13C NMR (CDCl3, 200 MHz, ppm) d 170.1, 139.3, 128.7,
128.4, 125.9, 76.9, 62.7, 38.7, 38.4.
66.09; H, 6.83; found: C, 65.99, 6.93; (S)-3a: [
CHCl3) corresponding to 72% ee determined by HPLC.
a
]
D = À36.6 (c 0.75,
4.7. Ethyl 3,5-dihydroxy-5-phenylpentanoate 4a
Acknowledgements
1H NMR (CDCl3, 400 MHz, ppm, dr 90:10) d 7.36–7.32 (m, 3H,
Ar), 7.28–7.24 (m, 2H, Ar), 5.13–5.09 (dd, 0.10 H), 4.97–4.94 (dd,
0.95H, J1 = 3.3 Hz, J2 = 9.7 Hz), 4.35–4.28 (m, 1H), 4.19–4.13 (q,
2H, OCH2CH3), 3.69 (s, 2H, OH), 2.53–2.44 (m, 2H), 1.97–1.88 (m,
1H), 1.79–1.74 (dt, 1H, J1 = 2.9 Hz, J2 = 14.4 Hz), 1.27–1.24 (t, 3H,
OCH2CH3); 13C NMR (CDCl3, 200 MHz, ppm) d 172.5, 144.1, 128.4,
127.5, 125.7, 74.4, 68.6, 60.8, 44.8, 41.5, 14.1; HR-MS (ESI, [M+H
+] calcd for: C13H18O4Na, 261.1103, found, 261.1101; (3S,5R)-4a:
This work was supported by COST Action CM1303 Systems Bio-
catalysis and Polish National Science Center project No. 2013/11/B/
ST5/02199.
A. Supplementary data
Supplementary data associated with this article can be found, in
the online version, at http://dx.doi.org/10.1016/j.tetasy.2017.05.
005.
[a]D = +17.5 (c 0.75, CHCl3) corresponding to 99% ee determined
by HPLC.
4.8. t-Butyl 3,5-dioxo-5-phenylpentanoate 1b
References
Ketone–enol equilibrium is shifted toward enol (92:8). 1H NMR
(CDCl3, 400 MHz, ppm, enol:ketone = 92:8) d 15.8 (br s, 0.9H, OH),
7.89–7.87 (d, 2H, Ar), 7.53–7.47 (m, 1H, Ar), 7.47–7.43 (m, 2H, Ar),
6.29 (s, 1H, CH), 3.39 (s, 2H), 1.49 (s, 9H, 3ÂCH3); 13C NMR (CDCl3,
100 MHz, ppm) d 189.7, 182.6, 166.8, 134.3, 132.5, 128.7, 127.1,
96.7, 82.0, 47.2, 28.0; HR-MS (ESI, [M+H+] calcd. for: C15H18O4Na,
1. a) Santaniello, E.; Ferraboschi, P.; Grisenti, P.; Manzocchi, A. Chem. Rev. 1992,
92, 1071–1140; b) Goldberg, F. W.; Kettle, J. G.; Kogej, T.; Perry, M. W.;
Tomkinson, N. P. Drug Discovery Today 2015, 20, 11–17.
2. Kulkarni, S. J.; Pedduri, Y.; Chittiboyina, A. G.; Avery, M. A. J. Org. Chem. 2010,
75, 3113–3116.
3. a) Goldberg, S.; Guo, Z.; Chen, S.; Goswami, A.; Patel, R. N. Enzyme Microb.
Technol. 2008, 43, 544–549; b) Edegger, K.; Stampfer, W.; Seisser, B.; Faber, K.;
_
Please cite this article in press as: Za˛dło-Dobrowolska, A. ; et al. Tetrahedron: Asymmetry (2017), http://dx.doi.org/10.1016/j.
tetasy.2017.05.005

_
6
A. Za˛dło-Dobrowolska et al. / Tetrahedron: Asymmetry xxx (2017) xxx–xxx
Mayer, S. F.; Oehrlein, R.; Hafner, A.; Kroutil, W. Eur. J. Org. Chem. 2006, 1904–
1909.
4. Patel, R. N.; Banerjee, A.; McNamee, C. G.; Brzozowski, D.; Hanson, R. L.; Szarka,
L. J. Enzyme Microb. Technol. 1993, 15, 1014.
13. a) Honda, T.; Ono, S.; Mizutani, H.; Hallinan, K. O. Tetrahedron: Asymmetry
1997, 8, 181–184; b) Zhou, L.; Liu, X.; Ji, J.; Zhang, Y.; Wu, W.; Liu, Y.; Lin, L.;
Feng, X. Org. Lett. 2014, 16, 3938–3941; c) Reiter, M.; Ropp, S.; Gouverneur, V.
Org. Lett. 2004, 6, 91–94.
5. a) Xu, Q.; Yu, J.; Han, F.; Hu, J.; Chen, W.; Yang, L. Tetrahedron: Asymmetry 2010,
21, 156–158; b) Clarke, P. A.; Santos, S.; Mistry, N.; Burroughs, L.; Humphries, A.
C. Org. Lett. 2011, 13, 624; c) Xie, Z.-B.; Wang, N.; Jiang, G.-F.; Yu, X.-Q.
Tetrahedron Lett. 2013, 54, 945–948; d) Li, H.-H.; He, Y.-H.; Guan, Z. Catal.
Commun. 2011, 12, 580–582; e) Xu, X.-Y.; Wang, Y.-Z.; Gong, L.-Z. Org. Lett.
2007, 9, 4247–4249; f) Machajewski, T. D.; Wong, C.-H. Angew. Chem., Int. Ed.
2000, 39, 1352–1374.
14. (a) Yin, J.; Kouda, K.; Tezuka, Y.; Le Tran, Q.; Miyahara, T.; Chen, Y.; Kadota, S.
Planta Med. 2004, 70, 54–58; (b) Sawant, K. B.; Jennings, M. P. J. Org. Chem.
2006, 71, 7911–7914; (c) Lee, K.; Kim, H.; Hong, J. Org. Lett. 2009, 11, 5202–
5205.
15. Sabitha, G.; Padmaja, P.; Yadav, J. S. Helv. Chim. Acta 2008, 91, 2235–2239.
16. Bonini, C.; Pucci, P.; Racioppi, R.; Viggiani, L. Tetrahedron: Asymmetry 1992, 3,
29–32.
6. Chu, C.; Morishita, K.; Tanaka, T.; Hayashi, M. Tetrahedron: Asymmetry 2006, 17,
2672–2677.
7. Grange, R. L.; Williams, C. M. Tetrahedron Lett. 2010, 51, 1158–1160.
8. Li, W.; Fan, W.; Ma, X.; Tao, X.; Li, X.; Xie, X.; Zhang, Z. Chem. Commun. 2012,
8976–8978.
9. a) Bariotaki, A.; Kalaitzakis, D.; Smonou, I. Org. Lett. 2012, 14, 1792–1795; b)
Wolberg, M.; Hummel, W.; Müller, M. Chem. Eur. J. 2001, 7, 4562–4571.
10. Xu, C.; Yuan, C. Tetrahedron 2005, 61, 2169–2186.
11. (a) Lüdeke, S.; Richter, M.; Müller, M. Adv. Synth. Catal. 2009, 351, 253–259; (b)
Ji, A.; Wolberg, M.; Hummel, W.; Wandrey, C.; Müller, M. Chem. Commun. 2001,
57–58.
17. Henkel, B.; Kunatk, A.; Schick, H. Tetrahedron: Asymmetry 1993, 4, 153–156.
18. Zadlo, A.; Schrittwieser, J. H.; Koszelewski, D.; Kroutil, W.; Ostaszewski, R. Eur.
J. Org. Chem. 2016, 2016, 1007–1011.
19. Voss, C. V.; Gruber, C. C.; Kroutil, W. Angew. Chem., Int. Ed. 2008, 47, 741–745.
20. a) Cui, J. N.; Teraoka, R.; Ema, T.; Sakai, T.; Utaka, M. Tetrahedron Lett. 1997, 38,
3021–3024; b) Rotthaus, O.; Kruger, D.; Demuth, M.; Schaffner, K. Tetrahedron
1997, 53, 935–938.
21. Clarke, P. A.; Martin, W. H. C.; Hargreaves, J. M.; Wilson, C.; Blake, A. J. Org.
Biomol. Chem. 2005, 3, 3551–3563.
12. (a) Gaikwad, R. D.; Rane, M. D.; Bhat, S. V. Tetrahedron: Asymmetry 2017, 28,
181–185; (b) Sabitha, G.; Gopal, P.; Yadav, J. S. Tetrahedron: Asymmetry 2009,
20, 1493–1499.
_
Please cite this article in press as: Za˛dło-Dobrowolska, A. ; et al. Tetrahedron: Asymmetry (2017), http://dx.doi.org/10.1016/j.
tetasy.2017.05.005