Regio- and stereoselective reduction of diketones and oxidation of diols by biocatalytic hydrogen transfer

Article abstract of DOI:10.1002/ejoc.200500839

The asymmetric reduction of symmetrical and nonsymmetrical diketones as well as the stereoselective oxidation of various diols by biocatalytic hydrogen transfer was investigated by employing lyophilized cells of Rhodococcus ruber DSM 44541 containing alcohol dehydrogense ADH-'A'. Symmetrical and nonsymmetrical diketones at the (ω-1)- and (ω-2)-positions are reduced to the Prelog product with high stereopreference, while sterically more demanding ketone moieties, for example those at the (ω-3)-position, remain unchanged. For the oxidation mode, differentiation between primary and secondary alcohols is achieved, and the (S)-configured secondary alcohols at the (ω-1)- and (ω-2)-positions are oxidized preferentially. Wiley-VCH Verlag GmbH & Co. KGaA, 2006.

Full text of DOI:10.1002/ejoc.200500839

FULL PAPER
DOI: 10.1002/ejoc.200500839
Regio- and Stereoselective Reduction of Diketones and Oxidation of Diols by
Biocatalytic Hydrogen Transfer
Klaus Edegger,[a,b] Wolfgang Stampfer,[a] Birgit Seisser,[a,b] Kurt Faber,[a,b]
Sandra F. Mayer,[c] Reinhold Oehrlein,[c] Andreas Hafner,[c] and Wolfgang Kroutil*[a,b]
Keywords: Biotransformations / Oxidation / Reduction / Hydrogen transfer / Diketones
The asymmetric reduction of symmetrical and nonsymmetri-
cal diketones as well as the stereoselective oxidation of vari-
ous diols by biocatalytic hydrogen transfer was investigated
by employing lyophilized cells of Rhodococcus ruber DSM
ties, for example those at the (ω-3)-position, remain un-
changed. For the oxidation mode, differentiation between
primary and secondary alcohols is achieved, and the (S)-con-
figured secondary alcohols at the (ω-1)- and (ω-2)-positions
44541 containing alcohol dehydrogense ADH-‘A’. Symmetri- are oxidized preferentially.
cal and nonsymmetrical diketones at the (ω-1)- and (ω-2)-
positions are reduced to the Prelog product with high stereo-
preference, while sterically more demanding ketone moie-
(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim,
Germany, 2006)
tified an exceptional, solvent-stable alcohol dehydrogenase
ADH-‘A’ from Rhodococcus ruber DSM 44541,[7] which is
ideally suited for biocatalytic hydrogen-transfer reactions[8]
that employ 2-propanol as the hydrogen donor for asym-
metric reduction[9] and acetone as the hydrogen acceptor
for oxidation.
In order to broaden the applicability of this method to
more complex bifunctional substrates, we investigated the
regio- and stereoselectivity of the reduction/oxidation of di-
ketones/diols. Special emphasis was placed on the influence
of the relative position of the functional groups to each
other.
Introduction
The regioselective reduction of one specific ketone moi-
ety out of all chemically equivalent ketone moieties within
the same molecule cannot easily be achieved by chemical
methods without the use of protection strategies.[1] The
same is true for the oxidation of one specific hydroxy group
out of all chemically equivalent hydroxy groups, although
methods that are selective to a certain extent have been re-
ported.[2] Biocatalysts show intrinsic high regio- and stereo-
selectivity and are therefore ideally suited catalysts for the
transformation of complex molecules possessing more than
one reactive group, without the need for protection tech-
niques. Chiral keto-alcohols are widespread structural fea-
tures of many natural products,[3] such as pheromones[3b] or
antitumor agents like discodermolide,[3c] and are therefore
frequently used chiral building blocks for fine chemicals in
the agrochemical-, flavor/fragrance-, and pharmaceutical
industry.[4] Furthermore non-racemic short-chain diols
serve as starting materials for chiral polymers[5] or as the
backbone for chiral ligands[4a] for asymmetric transition-
metal catalysis. Enantiopure diols and hydroxy ketones have
been biocatalytically synthesized by employing alcohol de-
hydrogenases from various sources.[4,6] We recently iden-
Results and Discussion
Asymmetric Bioreduction of Diketones
The (biocatalytic) reduction of diketones to diols pro-
ceeds in a stepwise fashion via the corresponding hydroxy
ketone, and the selectivities and reaction rates of both steps
determine the outcome of the reduction (Scheme 1). All ex-
periments were performed by employing lyophilized cells of
Rhodococcus ruber DSM 44541 containing the alcohol de-
hydrogenase ADH-‘A’ as the catalyst, while 2-propanol
(16% v/v) was used as the hydrogen donor, and also as the
co-solvent to improve the solubility of the substrates. The
reduction of the vicinal diketone 2,3-pentanedione (1a) ex-
clusively yielded the diol (2S,3R)-1c in high isolated yield
(93%) with a low ee (60%) but a high de (97%) (Table 1) –
no measurable amounts of the corresponding hydroxy
ketone were detected.
[a] Department of Chemistry, Organic and Bioorganic Chemistry,
University of Graz,
Heinrichstrasse 28, 8010 Graz, Austria
Fax: +43-316-380-9840
E-mail: Wolfgang.Kroutil@uni-graz.at
[b] Research Centre Applied Biocatalysis,
Graz, Austria
[c] CIBA SC Inc., K-420.2.20,
4002 Basel, Switzerland
Since a low stereoselectivity was previously observed for
Supporting information for this article is available on the
WWW under http://www.eurjoc.org or from the author.
R. ruber ADH-‘A’ for small substrates,[8a] we assumed that
1904
© 2006 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Org. Chem. 2006, 1904–1909

Regio- and Stereoselective Reduction of Diketones and Oxidation of Diols
FULL PAPER
Scheme 1. Reduction of diketones by biocatalytic hydrogen transfer.
Table 1. Biocatalytic reduction of diketones by hydrogen transfer with the use of Rhodococcus ruber DSM 44541.
Hydroxy ketone
Diol
Substrate
Conversion[a]
[%]
yield[b]
[%]
ee
[%]
yield[b]
[%]
ee
[%]
de
[%]
1a
2a
3a
4a
5a
95
95
97
85
65
1b
Ͻ0.1
39
90
23
38
–
97
Ͼ99
95
Ͼ99
(2S,3R)-1c
(2S,3R)-2c
–
(3S,4S)-4c
(2S,5S)-5c
93
52
Ͻ0.1
59
23
60
98
–
Ͼ99
Ͼ99
97
Ͼ99
–
Ͼ99
Ͼ99
(S)-2b
(S)-3b
(S)-4b
(S)-5b
[a] Based on the remaining diketone after 48 h conversion time. [b] isolated yield.
extension of the alkyl chain may lead to a higher selectivity: diminish the general excellent stereoselectivity of the re-
indeed 2,3-heptanedione (2a) was reduced to the diol duction of a given carbonyl group.
(2S,3R)-2c with excellent ee (98%) and de (Ͼ99%). For a
Consequently, the reduction technique was employed for
preparative substrate concentration of 350 m and a cell/ the symmetrical diketone 2,5-hexanedione (5a). The corre-
substrate ratio of 1:1, the obtained product mixture con- sponding enantiopure 2,5-hexanediol (5c) is a versatile
tained 39% hydroxy ketone (S)-2b (97% ee) and 52% diol building block for the synthesis of various chiral phosphane
(2S,3R)-2c after 48 h (Table 1). Sterically more demanding ligands that are used in chiral Wilkinson catalysts,[10] there-
keto-moieties, for instance that at the 4-position of 2,4-oc- fore various chemical[11] and biocatalytic[4a,6c,12] methods
tanedione (3a), were not accepted, therefore the reduction for its synthesis have been reported. In line with the obser-
of 3a proceeded only through a single step to furnish hy- vations mentioned above, the first reduction step of 5a oc-
droxy ketone (S)-3b in 90% isolated yield with an ee Ͼ curred with absolute stereoselectivity to yield the hydroxy
99%. In contrast, both keto-moieties of the symmetric dike- ketone (S)-5b with an ee Ͼ 99%. In addition, the second
tone 4a are at the (ω-2)-position and are therefore amenable reduction step to the corresponding diol (2S,5S)-5c was
to bioreduction. The first desymmetrisation reduction step also performed with absolute stereoselectivity (Ͼ99% ee,
of 4a occurred with a good stereoselectivity (ee 95%), and Ͼ99% de).
the second (kinetic resolution) step with a perfect stereo-
and enantioselectivity, since only the (S)-enantiomer of the
hydroxy ketone (S)-4b was reduced further to yield the op-
tically pure diol (3S,4S)-4c (ee and de Ͼ 99%). From these
Asymmetric Oxidation of 2,n-Alkane Diols
experiments, we concluded, for the reduction, that (i)
By switching from the hydrogen donor 2-propanol to the
ketone moieties at the (ω-1)- or (ω-2)-position can be ac- hydrogen acceptor acetone, stereoselective oxidations can
cepted, (ii) neighboring ketone or hydroxy groups do not be performed. Biocatalytic oxidation of the prochiral diol
Eur. J. Org. Chem. 2006, 1904–1909
© 2006 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjoc.org
1905

W. Kroutil et al.
FULL PAPER
meso-5c with R. ruber yielded the enantiopure hydroxy where (R)-5b was obtained. Because of the strong prefer-
ketone (R)-5b (Ͼ99% ee) (Scheme 2), which indicates that ence of ADH-‘A’ for (S)-configured alcohols, the intermedi-
ADH-‘A’ showed an exclusive preference for the (S)-config- ate (S)-hydroxy ketone (S)-5b was further converted to dike-
ured center of the two hydroxy moieties at the (ω-1) posi- tone 5a.
tion.
For nonsymmetric substituted diols a high regioselectiv-
ity in addition to the high recognition of (S)-centers was
observed, for instance, racemic (2R*,4R*)-3c was exclu-
sively oxidized at the (S)-configured (ω-1)-position to yield
the 4-hydroxy-2-octanone (S)-3d, thus no 2-hydroxy-4-oc-
tanone 3b was detectable. However, the close vicinity of the
two hydroxy groups led to a significant decrease in enantio-
selectivity (E) of the oxidation step (E = 3). A similar low
enantioselectivity was obtained for the oxidation of
(2R*,4S*)-3c (E = 4); however, in this case only hydroxy
Scheme 2. Biocatalytic oxidation by hydrogen transfer of meso-2,5-
hexanediol 5c.
By performing the oxidation for the racemic diol ketone was found as the oxidation product, and no diketone
(2R*,5R*)-5c, the picture becomes more complex, since we was detectable. For the vicinal diol (2R*,3R*)-6c similar re-
deal with a sequential oxidative kinetic resolution.[13] Under sults were obtained, thus the (S)-configured alcohol at the
the reaction conditions employed, the biocatalytic oxidation (ω-1)-position was oxidized first to give (S)-6d as the major
of racemic diol rac-(2R*,5R*)-5c yielded enantiopure hy- isomer. The intermediate hydroxy ketone 6d was oxidized
droxy ketone (S)-5b (Ͼ99% ee), a small amount of diketone further to yield a significant amount of diketone 6a (18%
(5%), and the remaining diol (2R,5R)-5c (97% ee) at 47% GC yield). The oxidative kinetic resolution of (2R*,3S*)-6c
conversion (Table 2). From these data, the enantioselectivity resulted in (R)-3-hydroxy-2-octanone (R)-6d as the mayor
of the first kinetic resolution step (E1) can be estimated to isomer, which is the male sex pheromone of the longhorn
be greater than 200.[14] As to be expected, for the oxidation beetle Anaglyptus subfasciatus.[3b] Nevertheless, the enantio-
of (2R*,5R*)-5c, we obtained the (S)-configured hydroxy selectivity of the first oxidation step was very low (E Ͻ 4).
ketone 5b, which is in contrast to the oxidation of meso-5c, In summary, (i) hydroxy moieties at either the (ω-1)- or the
Table 2. Biocatalytic oxidation of 1,2-alkane diols by hydrogen transfer with the use of Rhodococcus ruber DSM 44541.
Diketone
yield[b]
[%]
Hydroxy ketone
Remaining diol
yield[b]
[%]
Substrate
Conversion[a]
[%]
yield[b]
[%]
ee
[%]
ee
[%]
(2R*,4R*)-3c 42
(2R*,4S*)-3c 56
3a
3a
5a
5a
6a
6a
1
(S)-3d
(R)-3d
(R)-5b
(S)-5b
(S)-6d
(R)-6d
41
56
62
42
28
27
41
55
Ͼ99
Ͼ99
66
(2R,4R)-3c 58
(2R,4S)-3c 44
meso-5c 38
(2R,5R)-5c 53
(2R,3R)-6c 54
(2R,3S)-6c 73
25
24
n.a.
97
51
8
Ͻ0.1
Ͻ0.1
5
18
Ͻ0.1
meso-5c
62
(2R*,5R*)-5c 47
(2R*,3R*)-6c 46
(2R*,3S*)-6c 27
31
[a] Based on remaining diol after 48 h conversion time. [b] GC yield; n.a. = not applicable.
1906
www.eurjoc.org
© 2006 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Org. Chem. 2006, 1904–1909

Regio- and Stereoselective Reduction of Diketones and Oxidation of Diols
FULL PAPER
(ω-2)-position are accepted, and (ii) in contrast to the re- (ω-2)-position. Sterically more demanding ketone moieties,
duction mode, a neighboring hydroxy moiety diminishes the for example those at the (ω-3)-position, remained un-
enantioselectivity of the first oxidation step.
changed. For the oxidation mode, differentiation between
primary and secondary alcohols is achieved, and the (S)-
configured secondary alcohols at the (ω-1) and (ω-2)-posi-
tions are oxidized preferentially.
Regio- and Enantioselective Oxidation of 1,n-Alkane Diols
Enantioselective oxidation by biocatalytic hydrogen
transfer of diols rac-7c–12c bearing a secondary and pri-
mary alcohol moiety showed an exclusive selectivity for the
secondary alcohol moiety, while the primary hydroxy group
remained unchanged (Scheme 3). This offers a highly selec-
tive method to distinguish between primary and secondary
alcohols. While rac-7c turned out to be a nonsubstrate, the
other substrates underwent oxidative kinetic resolution.
The substrate structure/ enantioselectivity pattern was sim-
ilar to that of the sec,sec-diols described above; whereas low
E values were obtained when the hydroxy moieties are in
close proximity (rac-8c, 9c, 12c), good to excellent E values
were obtained for substrates with distant groups (rac-10c,
11c) (Table 3). As a rule of thumb, the minimum require-
ment for the spacer moiety between both hydroxy groups is
at least four to five methylene groups. In general, going in
line with internal diols, (S) enantiomers are preferentially
oxidized. For substrate 12c, the apparent opposite enanti-
opreference can be explained by a switch of the CIP pri-
ority.
Experimental Section
Diketones 1a–5a, as well as diols 5c, rac-7c–12c, and the precursors
(R)-ethyl-3-hydroxybutyrate and (S)-ethyl-lactate were available
commercially either from Sigma–Aldrich–Fluka (Vienna, Austria)
or Lancaster (Frankfurt am Main, Germany). The commercial
mixture of meso-2,5-hexanediol (meso-5c) and rac-2,5-hexanediol
[(2R*,5R*)-5c] was separated by silica gel chromatography (tolu-
ene/EtOAc = 1:1). The following all-rac-diols were obtained by re-
duction of the corresponding diketone with the appropriate
amount of NaBH4 in EtOH as described previously,[8a] and the
products were identified by comparison of the NMR data with that
from the literature: 2,3-pentanediol 1c,[15] 2,3-heptanediol 2c,[16]
and 3,4-hexanediol 4c.[17] Diols (2R*,3R*)-6c and (2R*,3S*)-6c
were synthesized as described starting from E- and Z-2-octene,
respectively.[18]
Optical rotations were measured on a Perkin–Elmer Polarimeter
341 in
a 1 mL cuvette with a 10 cm pathlength. Column
chromatography was performed using Merck 60 silica gel (40–
63 µ). 1H and 13C NMR spectra were recorded on a Bruker
360 MHz spectrometer at 360 and 90 MHz, respectively, using
TMS as internal standard. THF was freshly distilled before use
from sodium/potassium alloy under argon.
Lyophilized cells of Rhodococcus ruber DSM 44541 were obtained
by cultivating the organism in 250 mL of a complex medium
[10 gl–1 yeast extract (Oxoid L21), 10 gl–1 bacteriological peptone
(Oxoid L37), 10 gl–1 glucose (Fluka 49150), 2 gl–1 NaCl (Roth
9265.1), 0.15 gl–1 MgSO4·7H2O (Fluka 63140), 1.3 gl–1 NaH2PO4
(Fluka 71496), 4.4 gl–1 K2HPO4 (Merck 5101), distilled water] in
one liter baffled shake flasks at 30 °C at 120 rpm. After three days,
the cells were harvested by centrifugation (6000 rpm, 20 min),
washed with phosphate buffer (50 m, pH 7.5), shock frozen in
liquid nitrogen, and lyophilized.
Scheme 3. Regio- and enantioselective oxidation of a sec-alcohol
moiety in the presence of a primary alcohol by biocatalytic hydro-
gen transfer.
Table 3. Biocatalytic oxidation of 1,n-alkane diols by hydrogen
transfer with the use of Rhodococcus ruber DSM 44541.
General Procedure for Reduction by Biocatalytic Hydrogen Transfer
Lyophilized cells of R. ruber (0.25 g) were rehydrated in tris buffer
(5 mL, pH = 8, 50 m) at 130 rpm for 2 h at 30 °C. The substrate
(2.1 mmol) and 2-propanol (1 mL, 16.7 mmol) was added, and the
mixture was shaken at 30 °C (130 rpm) for 48 h. The products were
extracted with EtOAc and analyzed by GC. The solvent was re-
moved, and the products were purified by silica gel chromatog-
raphy.
Substrate
Conversion [%]
ee[c] [%]
E[d]
rac-7c
rac-8c
rac-9c
rac-10c
rac-11c
rac-12c
n.c.[a]
n.d.
n.d.
n.d.
4
Ͼ200
58
9[a]
20 (R)
34 (R)
99 (R)
90 (R)
11 (S)
42[a]
51[b]
50[b]
21[a]
3
General Procedure for Oxidation by Biocatalytic Hydrogen Transfer
[a] After 48 h conversion time. [b] After 24 h conversion time. [c] ee
of remaining alcohol. [d] Enantioselectivity calculated from conver-
sion and ee; n.d. = not determined because of too low conversion;
n.c. = no conversion.
Lyophilized cells of R. ruber (0.25 g) were rehydrated with tris
buffer (5 mL, pH = 8, 50 m) at 130 rpm for 2 h at 30 °C. The
substrate (1.4 mmol) and acetone (1 mL, 17 mmol) was added, and
the mixture was shaken at 30 °C (130 rpm) for 24/48 h. The prod-
ucts were extracted with EtOAc and analyzed by GC. The solvent
was evaporated under reduced pressure, and the crude products
were purified by silica gel chromatography.
Conclusions
Symmetrical and nonsymmetrical diketones can be re-
duced with high stereopreference, whereby ketone moieties
(2R*,4R*)-3c and (2R*,4S*)-3c: A diastereomeric mixture of
(2R*,4S*)-3c and (2R*,4R*)-3c (86/14) was synthesized as re-
at the (ω-1)-position are reduced faster than those at the ported.[19] In order to obtain a higher amount of the (2R*,4R*)-3c
Eur. J. Org. Chem. 2006, 1904–1909
© 2006 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjoc.org
1907

W. Kroutil et al.
FULL PAPER
diasteromer, 2,4-octanedione 3a (1.4 g, 9.8 mmol) was dissolved in
EtOH (20 mL, 96%), and Pt/C(160 mg, 5%) was added. The mix-
ture was stirred at 20 °C under H2 (1 atm, 13 d) until complete
conversion. The mixture was filtered, and the solvent evaporated
under reduced pressure. Silica gel chromatography afforded 0.59 g
stirred for 10 min to deprotonate the hydroxy group. n-Butylmag-
nesium bromide (4.25 mL, 8.5 mmol, 2  in Et2O) was added drop-
wise at 20 °C. The mixture was stirred for 5 h at 20 °C before satu-
rated aqueous NH4Cl (30 mL) was added, the phases were sepa-
rated and the organic phase containing (R)-2-hydroxy-4-octanone
(4.0 mmol, 41%) of (2R*,4S*)-3c and 0.44 g (3 mmol, 30%) of was extracted with diethyl ether, the combined organic layers were
(2R*,4R*)-3c. (2R*,4S*)-3c: 1H NMR (CDCl3): δ = 4.06 (m, 1 H),
3.86 (m, 1 H), 3.01 (bs, OH), 2.81 (bs, OH), 1.3–1.58 (m, 8 H), 1.21
(d, J = 6.2 Hz, 3 H), 0.92 (t, J = 6.8 Hz, 3 H) ppm. 13C NMR
(CDCl3): δ = 72.7, 68.8, 44.5, 37.8, 27.5, 24.0, 22.7, 14.0 ppm.
dried (Na2SO4), and the organic solvent was removed under re-
duced pressure. Without purification, the crude product was dis-
solved in diethyl ether (20 mL) and lithium aluminium hydride
(70 mg, 1.8 mmol) was added, and the mixture was stirred at 20 °C
for 3 h. The reaction was quenched with water, the solution was
extracted with EtOAc (3×30 mL), the combined organic phase was
dried (Na2SO4), purified by flash chromatography, and used as ref-
erence sample for chiral GC.
1
(2R*,4R*)-3c: H NMR (CDCl3): δ = 4.16 (hex, J = 8.8 Hz, 1 H),
3.94 (m, 1 H), 2.64 (bs, 2OH), 1.60 (t, J = 5.6 Hz, 2 H), 1.3–1.58
(m, 6 H), 1.24 (d, J = 6.3 Hz, 3 H), 0.91 (t, J = 6.9 Hz, 3 H) ppm.
13C NMR (CDCl3): δ = 69.2, 65.3, 44.1, 37.1, 28.0, 23.5, 22.7,
14.1 ppm.
The absolute configuration of (2R,3S)-6c and (2R,3R)-6c was as-
signed by chemical synthesis of (2S,3R*)-6c followed by co-injec-
tion with (2R*,3R*)-6c and (2R*,3S*)-6c, respectively, on chiral
GC. The synthesis of (2S,3R*)-6c was performed as described
above, but by using (S)-ethyl-lactate (1 g, 8.5 mmol) and pentyl-
magnesium bromide, prepared from pentyl bromide (1.2 g,
8.5 mmol) and Mg (0.21 g, 8.5 mmol). After workup, the desired
intermediate (S)-2-hydroxy-3-octanone was reduced with lithium
aluminium hydride as described above. The final product was used
as reference sample for chiral GC.
5-Hydroxy-2-pentanone (8b): 5-Hexenoic acid (115 mg, 1 mmol)
dissolved in dry THF (3 mL) was stirred under nitrogen at –30 °C.
Triethylamine (121 mg, 1.2 mmol) and 2-chloroethyl-chloro-formi-
ate (172 mg, 1.2 mmol) in THF (1 mL) were added dropwise. The
mixture was stirred at –20 °C for 45 min, then filtered and added
to a solution of NaBH4 (42 mg, 1.1 mmol) in THF/H2O (2 mL,
8:1). This mixture was stirred at 0 °C for 3 h, extracted with EtOAc,
and purified by flash chromatography to yield 5 mg (5%) of 8b as
reference material. Compound 8b was identified by comparison of
the 1H NMR spectroscopic data with that from the literature.[20]
13C NMR (90 MHz, CDCl3): δ = 207.1, 61.9, 40.2, 30.5, 24.7 ppm.
The absolute configuration of (S)-10c and (S)-11c was proven by
transforming the isolated enantio-enriched diol obtained from the
bio-oxidation by chemical methods to the corresponding 2-hep-
tanol/2-octanol, which was then compared by co-injection on chiral
GC with racemic and enantiopure 2-heptanol/2-octanol as pre-
viously reported.[8a] In a typical procedure, diol 11c (6 mg,
0.04 mmol) from the bio-oxidation was added to a mixture of pyri-
dine (0.5 mL) and tosyl chloride (7.5 mg, 0.04 mmol) in CH2Cl2
(1 mL) and stirred at 20 °C for 5 h. After addition of water, the
phases were separated, and the aqueous phase was again extracted
with CH2Cl2. The combined organic layers were dried (Na2SO4),
and the organic solvent was removed under reduced pressure. With-
out further purification, the product was dissolved in THF (3 mL),
LiAlH4 (30 mg, 0.8 mmol) was added, and the mixture was stirred
at 20 °C for 1 h. After quenching of the reaction by the addition
of water, the product was extracted with EtOAc and analyzed by
chiral GC.
The following hydroxy ketones were identified after the biocatalytic
reduction of the corresponding diketones by comparison of the
NMR spectroscopic data with the literature values: 2-hydroxy-3-
heptanone (2b),[21] 2-hydroxy-4-octanone (3b),[22] 4-hydroxy-3-
hexanone (4b),[23] 5-hydroxy-2-hexanone (5b).[6c]
The following compounds were identified after biocatalytic oxi-
dation of the corresponding diols by comparison of the NMR spec-
troscopic data with that from the literature: 4-hydroxy-2-octanone
(3d),[22,24] 3-hydroxy-2-octanone (6d),[25] 2,3-octanedione (6a),[25] 6-
hydroxy-2-hexanone (9b),[26] 7-hydroxy-2-heptanone (10b),[27] 8-hy-
droxy-2-octanone (11b).[28]
1-Hydroxy-2-octanone (12b): Cetyl pyridiniumchloride (2.0 g,
5.6 mmol) dissolved in 30% H2O2 (90 mL) was mixed with 12-
tungstophosphoric acid hydrate (5.2 g, 1.8 mmol) in 30% H2O2
(28 mL) and stirred at 40 °C for 2 h. The crude product was filtered
and washed with water to give peroxotungstophospate (2.2 g,
1.1 mmol, 61%) as a white, waxy solid. Peroxotungstophospate
(0.1 g, 0.05 mmol) was dissolved in 30% H2O2 (620 mg), and
CHCl3 (15 mL) and 1,2-octanediol (0.44 g, 3.0 mmol) was added
and heated to reflux for 16 h. The crude product was extracted with
EtOAc and purified by silica gel chromatography to yield 55 mg
12b (0.4 mmol, 13%), which was identified by comparison of the
NMR data with the literature data.[29]
Supporting Information (see footnote on the first page of this arti-
cle): Optical rotations, achiral and chiral GC data is available.
Acknowledgments
This study was performed within the Spezialforschungsbereich ‘Bio-
katalyse’ and the Research Centre Applied Biocatalysis. Financial
support by CIBA SC (Basel), Fonds zur Förderung der wissen-
schaftlichen Forschung (Vienna, project no. F115), TIG, SFG,
Province of Styria and City of Graz is gratefully acknowledged.
Proof of Absolute Configuration: The absolute configuration of the
following products was proven by comparison of the optical rota-
tion results with those from the literature (see Supporting Infor-
mation): 1c, 2b, 2c, 3b, 4b, 4c, 5b, 5c, 6d, 8c, 9c, 12c. The absolute
configuration of 3d was assigned by comparison of the elution or-
der on chiral GC (see Supporting Information).
[1] a) P. J. Kocienski, Protecting Groups, 3rd ed., Thieme, Stuttgart,
New York, 2004; b) T. W. Greene, P. G. M. Wuts, Protective
Groups in Organic Synthesis, 3rd ed., John Wiley & Sons, New
York, 1999; c) J. R. Hanson, Organic Synthetic Methods, The
Royal Society of Chemistry, Cambridge, 2002, pp. 126–141; d)
T. D. Nelson, R. D. Crouch, Synthesis 1996, 1031–1069; e) J.
Muzart, Synthesis 1993, 11–27.
[2] a) P. S. G. Tassignon, D. de Wit, T. C. de Rijk, L. F. De Buyck,
Tetrahedron 1995, 51, 11863–11872; b) A. Shaabani, M. J.
Ameri, J. Chem. Res. (S) 1998, 100–101; c) A. Liese, M. V.
The absolute configuration of (2R,4S)-3c and (2R,4R)-3c was as-
signed by independent chemical synthesis of (2R,4R*)-3c followed
by co-injection with (2R*,4R*)-3c and (2R*,4S*)-3c, respectively,
on chiral GC. For the synthesis of (2R,4R*)-3c, sodium hydride
(0.11 g, 4.2 mmol) was added to (R)-ethyl-3-hydroxybutyrate
(0.55 g, 4.2 mmol) in diethyl ether (20 mL) under nitrogen and
1908
www.eurjoc.org
© 2006 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Org. Chem. 2006, 1904–1909

Regio- and Stereoselective Reduction of Diketones and Oxidation of Diols
FULL PAPER
Filho, Curr. Opin. Biotechnol. 1999, 10, 595–603; d) J. Palou,
Chem. Soc. Rev. 1994, 23, 357–362; e) T. Schlama, K. Gabriel,
V. Gouverneur, C. Mioskowski, Angew. Chem. Int. Ed. Engl.
1997, 36, 2342–2344; f) C. F. M. Huntley, H. B. Wood, B.
Ganem, Tetrahedron Lett. 2000, 41, 2031–2034.
113, 8518–8519; c) M. J. Burk, J. E. Feaster, R. L. Harlow, Tet-
rahedron: Asymmetry 1991, 2, 569–592.
[11]
[12]
a) P. Saravanan, S. Raina, T. Sambamurthy, V. K. Singh, J. Org.
Chem. 1997, 62, 2669–2670; b) Q.-H. Fan, C.-H. Yeung,
A. S. C. Chan, Tetrahedron: Asymmetry 1997, 8, 4041–4045; c)
J. Bach, R. Berenguer, J. Garcia, M. Lopez, J. Manzanal, J.
Vilarrasa, Tetrahedron 1998, 54, 14947–14962.
a) K. J. Lieser, Synth. Commun. 1983, 13, 765–767; b) H. Na-
gai, T. Morimoto, K. Achiwa, Synlett 1994, 289–290; c) M.-J.
Kim, I. S. Lee, N. Jeong, Y. K. Choi, J. Org. Chem. 1993, 58,
6483–6485; d) J. Haberland, W. Hummel, T. Daussmann, A.
Liese, Org. Process Res. Dev. 2002, 6, 458–462 and references
cited therein.
[3] a) S. D. Rychnovsky, Chem. Rev. 1995, 95, 2021–2040; b) W. S.
Leal, X. Shi, K. Nakamuta, M. Ono, J. Meinwald, Proc. Natl.
Acad. Sci. USA 1995, 92, 1038–1042; c) M. Kalesse, ChemBi-
oChem 2000, 1, 171–175; d) M. Kalesse, M. Christmann, Syn-
thesis 2002, 981–1003; e) B. Jiang, Z. Chen, Tetrahedron: Asym-
metry 2001, 12, 2835–2843.
[4] a) J. Haberland, A. Kriegesmann, E. Wolfram, W. Hummel, A.
Liese, Appl. Microbiol. Biotechnol. 2002, 58, 595–599; b) A.
Matsuyama, H. Yamamoto, N. Kawada, Y. Kobayashi, J. Mol.
Catal. B: Enzym. 2001, 11, 513–521; c) A. Liese, K. Seelbach,
A. Buchholz, J. Haberland in Industrial Biotransformations
(Eds.: A. Liese, K. Seelbach, C. Wandrey), Wiley-VCH,
Weinheim, 2000, pp. 93–392.
[13]
[14]
W. Kroutil, A. Kleewein, K. Faber, Tetrahedron: Asymmetry
1997, 8, 3263–3274.
G. Caron, R. Kazlauskas, Tetrahedron: Asymmetry 1993, 4,
1995–2000.
[15]
[16]
D. Enders, S. Nakai, Chem. Ber. 1991, 124, 219–226.
W. Kroutil, M. Mischitz, K. Faber, J. Chem. Soc., Perkin Trans.
1 1997, 3629–3636.
W. Adam, B. Nestler, J. Am. Chem. Soc. 1993, 115, 5041–5049.
J. A. Katzenellenbogen, S. B. Bowlus, J. Org. Chem. 1973, 38,
627–632.
R. Aono, H. Kobayashi, Appl. Environ. Microbiol. 1997, 63,
3637–3642.
R. Münstedt, U. Wannagat, D. Wrobel, J. Organomet. Chem.
1984, 264, 135–148.
[5] G. N. Bennet, K. Y. San, Appl. Microbiol. Biotechnol. 2001, 55,
1–9.
[6] a) R. Bel-Rhlid, A. Fauve, M. F. Renard, H. Veschambre, Bio-
catalysis 1992, 6, 319–337; b) J.-X. Gu, Z.-Y. Li, G.-Q. Lin,
Tetrahedron 1993, 49, 5805–5816; c) H. Ikeda, E. Sato, T. Su-
gai, H. Ohta, Tetrahedron 1996, 52, 8113–8122.
[7] a) W. Stampfer, B. Kosjek, C. Moitzi, W. Kroutil, K. Faber,
Angew. Chem. Int. Ed. 2002, 41, 1014–1017; b) B. Kosjek, W.
Stampfer, M. Pogorevc, W. Goessler, K. Faber, W. Kroutil, Bi-
otechnol. Bioeng. 2004, 86, 55–62; c) W. Stampfer, B. Kosjek,
W. Kroutil, K. Faber, F. Niehaus, J. Eck (Ciba SC) WO
2005026338, 2005 [Chem. Abstr. 2005, 142, 331854].
[8] a) W. Stampfer, B. Kosjek, K. Faber, W. Kroutil, J. Org. Chem.
[17]
[18]
[19]
[20]
[21] N. S. Srinivasan, D. G. Lee, Synthesis 1979, 520–521.
[22] T. Kourouli, P. Kefalas, N. Ragoussis, V. Ragoussis, J. Org.
Chem. 2002, 67, 4615–4618.
2003, 68, 402–406; b) W. Stampfer, K. Edegger, B. Kosjek, K. [23] R. D. Chambers, J. Hutchinson, G. Sandford, A. Shah, J.
Faber, W. Kroutil, Adv. Synth. Catal. 2004, 346, 57–62.
[9] a) P. Hildebrandt, T. Riermeier, J. Altenbuchner, U. T.
Bornscheuer, Tetrahedron: Asymmetry 2001, 12, 1207–1210; b)
M. Wolberg, W. Hummel, C. Wandrey, M. Müller, Angew.
Chem. Int. Ed. 2000, 39, 4306–4308; c) T. Matsuda, Y. Naka-
jima, T. Harada, K. Nakamura, Tetrahedron: Asymmetry 2002,
13, 971–974; d) N. Itoh, M. Matsuda, M. Mabuchi, T. Dairi,
J. Wang, Eur. J. Biochem. 2002, 269, 2394–2402; e) C. Heiss,
R. S. Phillips, J. Chem. Soc., Perkin Trans. 1 2000, 2821–2825;
f) T. Schubert, W. Hummel, M. Müller, Angew. Chem. Int. Ed.
2002, 41, 634–637; g) A. Matsuyama, H. Yamamoto, Y. Kobay-
ashi, Org. Process Res. Dev. 2002, 6, 558–561.
Vaughan, Tetrahedron 1997, 53, 15833–15842.
[24] M. Miyashita, T. Suzuki, M. Hoshino, A. Yoshikoshi, Tetrahe-
dron 1997, 53, 12469–12486.
[25] O. Bortolini, G. Fantin, M. Fogagnolo, P. P. Giovannini, A.
Guerrini, A. Medici, J. Org. Chem. 1997, 62, 1854–1856.
[26] I. Fleming, P. Maiti, C. Ramarao, Org. Biomol. Chem. 2003, 1,
3989–4004.
[27] D. Barbry, C. Faven, A. Ajana, Synth. Commun. 1993, 23,
2647–2658.
[28] T. Takahashi, H. Ikeda, J. Tsuji, Tetrahedron Lett. 1980, 21,
3885–3888.
[29] B. Plietker, Org. Lett. 2004, 6, 289–291.
[10] a) M. J. Burk, J. E. Feaster, R. L. Harlow, Organometallics
1990, 9, 2653–2655; b) M. J. Burk, J. Am. Chem. Soc. 1991,
Received: October 27, 2005
Published Online: February 23, 2006
Eur. J. Org. Chem. 2006, 1904–1909
© 2006 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjoc.org
1909