CAL-B-Catalyzed Enantioselective Deacetylation of Some Benzylic Acetate Derivatives Via Alcoholysis in Non-aqueous Media

Article abstract of DOI:10.1007/s10562-014-1470-7

Enantioselective deacetylation of a set of benzylic acetates via alcoholysis catalyzed by Lipase B from Candida antarctica (CAL-B), under mild conditions is described. A systematic study allows to determine the appropriate combination nucleophile/organic solvent and also to explain the influence of these parameters on the enzymatic catalytic reaction. In all cases, (R)-alcohols are obtained with high ee (up to >99 %) at conversion 36 % < C < 48 %, the selectivity reaching E > 500. The enzymatic reactivity is influenced by the hydrophobicity of solvent and the structure/nature of the nucleophile. Furthermore, CAL-B allows enantio-complementary between transesterifications in non-aqueous media: alcoholysis and acetylation.

Full text of DOI:10.1007/s10562-014-1470-7

Catal Lett
DOI 10.1007/s10562-014-1470-7
CAL-B-Catalyzed Enantioselective Deacetylation of Some Benzylic
Acetate Derivatives Via Alcoholysis in Non-aqueous Media
•
•
Amna Za¨ıdi Mounia Merabet-Khelassi
Louisa Aribi-Zouioueche
Received: 8 October 2014 / Accepted: 23 December 2014
Ó Springer Science+Business Media New York 2015
Abstract Enantioselective deacetylation of a set of ben-
zylic acetates via alcoholysis catalyzed by Lipase B from
Candida antarctica (CAL-B), under mild conditions is
described. A systematic study allows to determine the
appropriate combination nucleophile/organic solvent and
also to explain the influence of these parameters on the
enzymatic catalytic reaction. In all cases, (R)-alcohols are
obtained with high ee (up to [99 %) at conversion 36 %
\ C \ 48 %, the selectivity reaching E [ 500. The
enzymatic reactivity is influenced by the hydrophobicity of
solvent and the structure/nature of the nucleophile. Fur-
thermore, CAL-B allows enantio-complementary between
transesterifications in non-aqueous media: alcoholysis and
acetylation.
Graphical Abstract
ROH
Solvent
Conversion Selectivity
2-BuOH DIPE 42%<C<45%
MeOH Toluene 42%<C<45%
E>500
E>500
Keywords Deacetylation ꢀ Alcoholysis ꢀ Lipases ꢀ
Kinetic resolution ꢀ Benzylic acetates ꢀ Non-aqueous media
1 Introduction
The use of enzymes as effective catalysts tools in organic
synthesis allows access to chiral molecules under mild and
eco-compatible conditions [1–4]. The enzymatic kinetic
resolution is commonly used to prepare a broad range of
chiral building blocks, required in several domains, such as
the manufacture of pharmaceuticals, cosmetics, flavors,
agricultural and fine chemicals [5–7]. Especially benzylic
alcohols are needed as key precursors for the generation of
pharmaceuticals [8]. They can be obtained under enantio-
pure or enantiomeric enriched form by transesterification in
organic solvents (acetylation or alcoholysis) [9, 10], or by
enzymatic hydrolysis in aqueous or biphasic media,
although deacetylation was scarcely investigated [11–15].
This may be an interesting way to be inserted into de-
racemization process, since efficient methods have been
developed over the last decade and bring new pathways for
Electronic supplementary material The online version of this
article (doi:10.1007/s10562-014-1470-7) contains supplementary
material, which is available to authorized users.
¨
A. Zaıdi ꢀ M. Merabet-Khelassi ꢀ L. Aribi-Zouioueche (&)
Ecocompatible Asymmetric Catalysis Laboratory (L.C.A.E),
Badji Mokhtar Annaba-University, B.P 12, 23000 Annaba,
Algeria
e-mail: louisa.zouioueche@univ-annaba.dz;
louisa.zouioueche@gmail.com
¨
A. Zaıdi
e-mail: zaidi.amna4@gmail.com
M. Merabet-Khelassi
e-mail: mounia.merabet@univ-annaba.dz
123

¨
A. Zaıdi et al.
the production of enantioenriched molecules with high
yields and selectivities [16–18].
from Aldrich. Specific activity[10,000 U/g used without any
pre-treatment. The monitoring of the reactions was conducted
using TLC on Silica gel 60F254 plates type MERCK 5179,
250 mesh. The separation of the resulting alcohols and the
remaining acetates was performed by column chromatogra-
Previously, we have shown that the control of several
parameterssuchas the amountofenzymeand the nature ofthe
acetylating agent dramatically affects both reactivity and
selectivity of the Candida antarctica lipase B (CAL-B) cata-
lyzed kinetic resolution through transesterification [19–22].
We have demonstrated that the efficiency of the enzymatic
acetylation is multifactorial, several parameters interact
simultaneously on both enzymatic reactivity and selectivity.
We supposed that the decrease of selectivity caused by
reducing the amount of enzyme was probably due to com-
petitive hydrolysis reactions in non aqueous media by the
water brought by enzyme [20]. Similarly, we have recently
revealed that the use of carbonate salts in the enzymatic
hydrolysis of racemic acetates with CAL-B, in non aqueous
media, allows a significant enhancement of the reactivity and
selectivity of this lipase. Due to the high enantioselectivity of
this hydrolysis with large series of substrates, deracemization
via Mitsunobu inversion protocol was investigated [23, 24].
In the continuity of our investigations, with the aim to
understand the mode of action of CAL-B and to clarify last
observations related to hydrolysis competition, we have stud-
ied several possibilities to deacetylate acetates (Scheme 1).
In the present paper, we describe the enantioselective
deacetylation of some benzylic acetates via alcoholysis
catalyzed by CAL-B (Scheme 1, path C), a less studied path
[27–36]. The influence of several parameters such as: the
nature of the acetyl acceptor, the organic solvent and water
on the progress of the enzymatic alcoholysis were exam-
ined in order to obtain optically pure alcohols.
˚
phy using Silica gel 60 A, 70–230 mesh 63–200 lm.
2.2 Instrumentations
The spectroscopic characterisation was performed with
1
Bru¨ker spectrometers (300 MHz for H, 75 MHz for 13C).
Chemical shifts were reported in d ppm from tetrameth-
ylsilane with the solvent resonance as internal standard for
1H NMR and chloroform-d (d 77.0 ppm) for 13C NMR. IR
spectra were recorded on Shimadzu FTIR-8400S spec-
¨
trometer. Melting points were measured using BUCHI
MELTING POINT B-545. The enantiomeric excesses were
measured by gas chromatography on ThermoFinnigan
Trace GC, equipped with an automatic autosampler and
using a CHIRALSIL-DEX CB column (25 m; 0.25 mm;
0.25 lm). Retention times are reported in minutes.
2.3 General Procedure for the Reduction of Ketones
The racemic alcohols were obtained after reduction of the
corresponding ketones using an excess of LiAlH4 diluted in
anhydrous ether or with NaBH4 in (THF/water; 4/1 v/v). The
reaction mixture was stirred under at 0 °C. The evolution of
the reactions was monitored by TLC. After total consump-
tion of ketones, the resulting alcohols were obtained pure in
good yields after standard work up. All spectroscopic ana-
lysis were detailed in the supplementary data.
2 Experimental Sections
2.4 General Procedure for the Chemical Acetylation
of Racemic Alcohols (1–7)
2.1 Chemicals and Materials
The racemic acetates (1a–7a) were obtained by standard
classical chemical acetylation of corresponding alcohols,
according to the following procedure: to 1 equivalent of
racemic alcohol (1–7), 1.2 equivalent of triethylamine and
0.1 equivalent of dimethylaminopyridine (DMAP) dis-
solved in 4 mL of ether, 1.5 equivalent acetic anhydride
were added slowly. The evolution of the reactions was
monitored by TLC. The acetates are obtained pure after
standard work up, in good yields. All spectroscopic ana-
lysis were detailed in the supplementary data.
All reagents and solvents were of analytical grade and were
purchased from Sigma-Aldrich. The Candida antarctica
lipase immobilized on acrylic resine CAL-B was purchased
2.5 General Procedure for the Alcoholysis of Racemic
Acetates (1a–7a) with Candida antarctica- B
lipase
To 1 mmol of the racemic acetates (1a–7a) dissolved in
2 mL of organic solvent, 2 mmol of the appropriate alcohol
Scheme 1 Possible pathways for enzymatic deacetylation of acetate
123

CAL-B-Catalyzed Enantioselective Deacetylation
and 12 mg of CAL-B, are added. The suspension was
stirred at 40 °C for 24 h. The reaction mixture is filtered on
Celite and concentrated in vacuo. The remaining acetate
and the producing alcohol were separated by chromatog-
raphy on silica gel (petroleum ether/ethyl acetate: 80/20)
and analyzed by chiral GC. The same procedure was fol-
lowed for the reactions in the presence of 60 mg of
catalytic amount of CAL-B, in the appropriate organic
solvent (Scheme 2).
The conversion and selectivity of the kinetic resolution
were quantified by chiral chromatography, and the results
are collected in Table 1.
The data from Table 1 showed high selectivity of CAL-
B catalyzed deacylation of (1a) with selectivity factor
values reaching E [ 500 in favor of the (R)-alcohol
enantiomer in all cases. It is to be reported that neither
alcoholysis or hydrolysis was observed without enzyme, in
both used solvents. On the other hand, a significant con-
version rates (respectively 14.7 and 11.2 %, entries 1 and
9) of (1a) deacetylation was recorded without use of
alcohols, which strengthens our hypothesis concerning the
existence of competitive hydrolysis reactions in non
aqueous media [23]. The reactivity was modulated by the
nature of the nucleophile and the length of the carbon
chain, whether in DIPE or in toluene, conversion vary
between 14 % \ C \ 44 %. Using primary alcohols in
DIPE, the reaction rate increases with the length of the
chain of the nucleophile. With n-propanol 40.9 % con-
version is observed compared to 22.1 % in methanol
(entry 4 vs. 2), but conversion decreases (15 %) in pre-
sence of n-butanol (entry 5). The best conversion was
noted with 2-butanol in DIPE (C = 43.5 %) and (R)-
alcohol was obtained with enantiomeric excess eep [99 %
(entry 7).
˚
molecular sieves 4 A.
3 Results and Discussion
The effect of both nucleophile and the organic solvent on the
deacetylationviaalcoholysisofphenylethylacetate(1a), have
been studied. These parameters should have strong influences
on the selectivity of the CAL-B in catalyzed kinetic resolution.
Thus seven alcohols with different structures were selected,
methanol, ethanol, n-propanol, n-butanol, 2-propanol,
2-butanol, t-butanol and two organic solvents with different
hydrophobicities: di-isopropylether and toluene.
3.1 Influence of the Nature of Nucleophile
on the Enzymatic Alcoholysis of 1-Phenylethyl
Acetate (1a)
Alcoholysis of racemic phenylethyl acetate (1a) by the
selected alcohols was performed in the presence of
Scheme 2 Enzymatic
alcoholysis of 1-phenylethyl
acetate (1a)
R-OHa
Solvent (logP)
Ee(S) (%)b
Ee(P) (%)b
Cc
Ec
Table 1 Influence of the nature
of the nucleophile on
Entry
the enzymatic alcoholysis of
1-phenylethyl acetate (1a)
1
–
DIPE
(1.9)
17.2
28.4
45.2
69.2
18.1
72.2
77
99.9
99.9
99.9
99.9
99.9
99.9
99.9
99.9
99.9
99.4
96.9
99.9
99.9
99.9
99.9
99.9
14.7
22.1
31.2
40.9
15.3
42.0
43.5
32.3
11.2
20.3
32.1
39.6
40.0
38.6
42.6
33.3
[500
[500
[500
[500
[500
[500
[500
[500
[500
400
2
MeOH
EtOH
3
4
n-PrOH
n-BuOH
2-PrOH
2-BuOH
t-BuOH
Sans
5
a
Reaction conditions: 1 mmol
6
of racemic acetate, 2 mmol of
alcohol, 12 mg of CAL-B, in
2 mL of organic solvent at
40 °C
7
8
47.6
12.6
25.3
45.8
65.4
66.7
62.7
74.2
49.8
9
PhMe
(2.5)
b
10
11
12
13
14
15
16
MeOH
EtOH
Enantiomeric excess of
recovered alcohols and
remaining acetates are measured
by chiral GC (ee = |R-S|/
|R ? S|)
99
n-PrOH
n-BuOH
2-PrOH
2-BuOH
t-BuOH
[500
[500
[500
[500
[500
c
Conversion: C = eeS/
eeP ? ees; Selectivity: E = Ln
[(1-C) (1-ee(S))]/Ln [(1-C)
(1 ? ee(S))] [25, 26]
123

¨
A. Zaıdi et al.
Likewise, with toluene as organic solvent, we observed
a direct relationship between the deacetylation efficiency of
the 1-phenylethyl acetate (1a) through CAL-B alcoholysis,
and the length of the alcohol alkyl radical, without any
exception (entries 10–13). Similar observations when using
DIPE as organic medium were recorded during the alco-
holysis of (1a) by secondary and tertiary alcohols (entries
6, 7 and 8 vs. 14, 15 and 16), and like with DIPE, the
deacetylation using 2-butanol gave the highest reaction rate
C = 42.6 % with (R)-alcohol enantiopreference (entry15).
Furthermore, DIPE and toluene used as solvent gave sim-
ilar results with the tertiary alcohol: t-BuOH (32.3 and
33.3 % for C, entries 8 and 16). This result should be
appealing, since this nucleophile is usually employed as
inert solvent in enzymatic catalysis [33, 37, 38] or as co-
solvent in enzymatic hydrolysis of 1-phenylethyl acetate
(1a) in biphasic systems [39]. These results suggest that
this alcohol could perform secondary reactions in enzy-
matic reactions processes.
all cases. Indeed, either the nature of the nucleophile or the
hydrophobicity of the solvent modulate the reactivity of
CAL-B
catalyzed
deacetylation
of
(1a)
(18 % \ C < 47.8 %). This is probably due to the addition
of molecular sieves which reduces the amount of water
introduced by the solvent, the reagents or the immobilized
enzyme. This limits the competition between nucleophiles
present in the reaction suspension: alcohol and water. The
highest conversion was achieved using ethanol in DIPE:
C = 47.8 % (entry 3). With the primary acetyl acceptor,
CAL-B reactivity depends on the length of the alkyl radical.
The same effect, was recently reported in the course of the
enzymatic esterification of mandelic acid [43]. This effect is
more important in toluene (entries 2–5 vs. 10–13). Using the
tertiary alcohol, the reaction rate was markedly decreased
(entries 8, 16), it must be underlined, that the best results
were recorded with the primary and secondary alcohols.
Furthermore, as shown in the results depicted in Table 2
the alcoholysis of acetates (2a–3a) presents similarities
with those obtained with (1a). With acetates (2a) and (3a),
the optimal conversions were obtained using 2-BuOH in
DIPE and with MeOH in toluene [entries 22, 24 for (2a)
and entries 36, 38 for (3a)]. These results indicate a sig-
nificant dependence hhacetyl acceptor/hydrophobicity of
solvent ii for the catalytic deacetylation catalyzed by CAL-
B (Fig. 1).
3.2 Effect of Molecular Sieves on the Enzymatic
Alcoholysis of Benzylic Acetates (1a–3a)
In order to reduce the competition between the nucleo-
philes present in reaction media (Water/ROH), and regulate
the enzymatic catalysis, we have added molecular sieves
˚
4 A, which have indeed shown an effect on both reactivity
and selectivity of Candida Rugosa Lipase (CRL) in
transesterification [21]. Thus the addition of the molecular
sieves was investigated for the alcoholysis of the phenyl-
ethyl acetate [40, 41], the substrate model of our study, as
well as for two other acetates [8, 42] (1a–3a).
3.3 Deacetylation via CAL-B Alcoholysis of Some
Acetate Precursors of Drugs (1a–7a)
In order to examine if the promising results obtained with
acetates (1a–3a) could be extended to a wider scope of
substrate, we have decided to test the same experimental
conditions with benzylic acetates of well-known pharma-
cotherapeutic interest. With the suitable deacetylation
conditions above described, we have performed a series of
reactions on racemic acetates (1a–7a), with 2-BuOH in
DIPE and methanol in toluene. The enantiomeric excesses
of the recovered acetates and the produced alcohols were
evaluated by chiral chromatography. The isolated chemical
yields of products were measured after separation by
chromatography on silica gel. The results are collected in
Table 3.
Each enzymatic alcoholysis reaction was carried out
according to Sect. 2.5 (Scheme 3). The progress and the
selectivity of the kinetic resolution were analyzed by chiral
chromatography, and the results are summarized in
Table 2.
As shown in Table 2, the addition of molecular sieves
with both solvents, strongly improves the alcoholysis rate of
the deacylation of acetate (1a) using the CAL-B. The
deacetylation was extremely enantioselective (E [ 500) in
The data from Table 3 show that CAL-B catalyzed
alcoholysis of racemic acetate (1a–7a) in organic medium
is highly enantioselective. The conversion rates vary
between 40 % \ C \ 48 % and E [ 500 under the tested
reaction conditions. The CAL-B reactivity is modulated by
the combination of two factors: the nature of alcohol
(ROH) and the hydrophobicity of the solvent used for the
enzymatic catalytic deacetylation. The lipase produced the
(R)-alcohols enantiomerically pure in satisfying isolated
chemical yields. These results validate the efficiency of our
Scheme 3 Enzymatic alcoholysis of acetates (1a–3a)
123

CAL-B-Catalyzed Enantioselective Deacetylation
Table 2 Enzymatic alcoholysis
of acetates (1a–3a) with
different nucleophiles in the
presence of molecular sieves
˚
4 A
a
Reaction conditions: 1 mmol
of racemic acetate, 2 mmol of
alcohol, 12 mg of CAL-B,
˚
60 mg of MS 4 A in 2 mL of
organic solvent at 40 °C
b
Enantiomeric excess of
recovered alcohols and
remaining acetates are measured
by chiral GC (ee = |R-S|/
|R ? S|)
c
Conversion: C = eeS/
eeP ? ees; Selectivity: E = Ln
[(1-C) (1-ee(S))]/Ln [(1-C)
(1 ? ee(S))]. [25, 26]
d
No reaction
123

¨
A. Zaıdi et al.
Fig. 1 Influence of the carbon chain length of the alcohol on conversion for the enzymatic alcoholysis of (1a)
Entry Substratea
ROH
Solvant (logP) Ee(S)(%)b
Yield (%)d
ee(P)(%)b Yield (%)d Cc
Ec
Table 3 Scope of enzymatic
alcoholysis of benzylic acetates
(1a–7a)
1
2
2-BuOH DIPE (1.9)
MeOH PhMe (2.5)
78.7 (36.6) 99.9 (38.9)
73.8 (35.5) 99.9 (25.6)
44.1 [500
42.5 [500
3
4
2-BuOH DIPE (1.9)
MeOH PhMe (2.5)
76.9 (44.5) 99.9 (21.3)
82.3 (36.5) 99.9 (32.6)
43.5 [500
45.2 [500
5
6
2-BuOH DIPE (1.9)
MeOH PhMe (2.5)
78.9 (30.8) 99.9 (19.5)
90.5 (18.8) 99.9 (33.5)
44.1 [500
47.5 [500
7
8
2-BuOH DIPE (1.9)
MeOH PhMe (2.5)
79.7 (43.3) 99.9 (21.9)
65.9 (49.6) 99.9 (34)
44.4 [500
39.8 [500
a
Reaction conditions: 1 mmol
of racemic acetate, 2 mmol of
alcohol, 12 mg of CAL-B,
˚
60 mg of MS 4 A in 2 mL of
9
2-BuOH DIPE (1.9)
MeOH PhMe (2.5)
83.4 (20.4) 99.9 (34.9)
81.8 (52.2) 99.9 (42.8)
45.5 [500
45.0 [500
organic solvent at 40 °C
10
b
Enantiomeric excess of
recovered alcohols and
remaining acetates are measured
by chiral GC (ee = |R-S|/
|R ? S|)
11
12
2-BuOH DIPE (1.9)
MeOH PhMe (2.5)
75.8 (16.2) 99.9 (30.5)
77.3 (44.8) 99.9 (41.6)
43.1 [500
43.6 [500
c
Conversion: C = eeS/
13
14
2-BuOH DIPE (1.9)
MeOH PhMe (2.5)
73.7 (50.8) 99.9 (37.1)
57.3 (48.9) 99.9 (24.9)
42.5 [500
36.5 [500
eeP ? ees; Selectivity: E = Ln
[(1-C) (1-ee(S))]/Ln [(1-C)
(1 ? ee(S))]. [25, 26]
d
Isolated yields
123

CAL-B-Catalyzed Enantioselective Deacetylation
Scheme 4 Enzymatic
transesterification versus
alcoholysis of (1a)
deacetylation conditions for enzymatic alcoholysis of
1-phenylethyl acetate (1a).
by the results obtained by t-butanol used as nucleophile in
the alcoholysis of acetates, which shows the influence of
alcohol structure on conversion. The results of the alco-
holysis catalyzed by CAL-B of a series of benzylic acetates
show thus a perfect enantiocomplementary with the enzy-
matic transesterification studied by our team.
A comparison of the results using CAL-B as an efficient
biocatalyst in both alcoholysis of phenylthyl acetate (1a)
and transesterification of the corresponding alcohol (1)
with isopropenyl acetate reveals a perfect enantiocomple-
mentary of those reactions in favor of the (R)-enantiomer
(Scheme 4). Moreover, the alcoholysis reaction appears as
an interesting alternative path, complementary to the
hydrolysis for resolving acetates. This study contributes to
the understanding of factors that significantly affect play a
role in the CAL-B catalyzed alcoholysis.
Finally, the improved alcoholysis conditions described
appear to be an efficient pathway for enzymatic deacety-
lation of acetates which offers many opportunities for
development, particularly interesting to insert in derace-
mization processes.
Acknowledgments Algerian Ministry of Higher Education and
Scientific Research (MESRS, FNR 2000) and ANDRU (PNR) are
gratefully acknowledged for financial support of this work. Prof.
Olivier RIANT (IMCN/Louvain Catholic University -UCL- Louvain-
La-Neuve, Belgium) is acknowledged for his help and the welcome of
4 Conclusions
¨
Amna ZAIDI and Mounia MERABET to perform specific analyses.
We have examined the effect of two important parameters
on the enzymatic alcoholysis of a set of benzylic acetates
using candida antarctica lipase (CAL-B): the nature of the
nucleophile and the hydrophobicity of the solvent. We have
optimized these parameters and achieved a highly selective
enzymatic deacetylation reaction. In all cases, high selec-
tivity factor values E [ 500, with (R)-enantiopreference
were recorded. CAL-B reactivity is dependent upon the
nature of nucleophile (ROH) whatever the solvent
employed. As expected, the primary and secondary alco-
hols exhibit the best conversion rates C [ 40 %, and
selectivities E [ 500 in kinetic resolution via alcoholysis
by the CAL-B lipase in both explored solvents. The addi-
References
1. Anastas PT, Warner JC (1998) Green chemistry: theory and
practice. Oxford University Press, New York
2. Anastas PT, Li PT (2010) In: Yukawa H, Blaschek H (eds) Water
as a green solvent. Wiley, New York
3. Anastas PT, Eghbali N (2010) Chem Soc Rev 39:301
4. Trost BM (1995) Angew Chem Int Ed 107:285
5. Carrea G, Riva S (2000) Angew Chem Int Ed 39:2226
6. Faber K (2011) Biotransformations in organic chemistry, 6th edn.
Springer, Berlin
7. Patel RN (2003) Curr Opin Drug Discov Dev 6:902
8. Patel RN (2008) Coord Chem Rev 252:659
˚
tion of molecular sieves 4 A decreasing the amount of
9. Ahmed M, Kelly T, Ghanem A (2012) Tetrahedron 68:6781
10. Pan J, Yu HL, Xu JH, Lin GQ (2011) Advances in biocatalysis:
enzymatic reactions and their applications. In: Ma S (ed)
Asymmetric catalysis from a Chinese perspective. Springer,
Berlin, pp 67–103
water, enhances the enzymatic reactivity. The best results
were recorded using 2-BuOH in DIPE and MeOH in tol-
uene, indicating dependence hhacetyl acceptor/hydropho-
bicity of solventii. The novelty of this study is represented
11. Aribi-Zouioueche L, Fiaud JC (2000) Tetrahedron Lett 41:4085
123

¨
A. Zaıdi et al.
12. Bidjou C, Aribi-Zouioueche L, Fiaud JC (2002) Tetrahedron Lett
43:3025
13. Bora PP, Bez G, Anal JMH (2011) J Mol Catal B 72:270
14. Kumaragura T, Fadnavis NW (2012) Tetrahedron 23:775
15. Bouzemi N, Grib I, Houiene Z, Aribi-Zouioueche L (2014)
Catalysts 4:215
27. Baldessari A, Iglesias LE (2012) Methods Mol Biol 861:457
28. Zhang J, Wu J, Yang L (2004) J Mol Catal B 31:67
29. Tosa M, Pilbak S, Moldovan P, Paizs C, Szatzker G, Szakacs G,
Novak L, Irimie FD, Poppe L (2008) Tetrahedron 19:1844
30. Kawasaki M, Nakamura K, Kawabata S (1999) J Mol Catal B
6:447
16. Turner NJ (2003) Curr Opin Biotechnol 14:401
17. Kamal A, Azhar MA, Krishnaji T, Malik MH, Azeeza S (2008)
Coord Chem Rev 252:569
31. Zhou R, Xu JH (2005) Biochem Eng J 23:11
32. Kato K, Gong Y, Irimescu R, Saito T, Yokogawa Y (2002)
Biotechnol Lett 24:1623
18. Merabet-Khelassi M, Vriamont N, Riant O, Aribi-Zouioueche L
(2011) Tetrahedron 22:1790
19. Bouzemi N, Debbeche H, Aribi-Zouioueche L, Fiand JC (2004)
Tetrahedron Lett 45:627
20. Merabet-Khelassi M, Bouzemi N, Fiaud JC, Riant O, Aribi-
Zouioueche L (2011) C R Chim 14:978
33. Schieweck F, Altenbach HJ (1998) Tetrahedron 9:403
34. Bencze LC, Paizs C, Tos MI, Trif M, Irimie FD (2010) Tetra-
hedron 21:1999
35. Brem J, Pilbak S, Paizs C, Banoczi G, Irimie FD, Tos MI, Poppe
L (2011) Tetrahedron 22:916
36. Faigl F, Kovacs E, Balogh D, Holczbauer T, Czugler M, Simandi
B (2014) Central Eur J Chem 12(1):25
37. Kitaguchi H, Fitzpatrick PA, Huber JE, Klibanov AM (1989) J
Am Chem Soc 111:3094
38. Woudenberg-van Oosterom M, van Rantwijk F, Sheldon RA
(1996) Biotechnol Bioeng 49:328
39. Fan Y, Xie Z, Zhang H, Qian J (2011) Kinet Catal 52(5):686
40. Suan CL, Sarmidi MR (2004) J Mol Catal B 28:111
41. Zilbeyaz K, Taskin M, Kurbanoglu EB, Kurbanoglu NI, Kilic H
(2010) Chirality 22:543
42. Sheldon RA (1996) J Chem Tech Biotechnol 67:1
43. Pan Y, Tang K-W, He C-Q, Yi W, Zhu W, Liu Y-N (2014)
Biotechnol Appl Biochem 61:274
21. Merabet-Khelassi M, Aribi-Zouioueche L, Riant
Tetrahedron 19:2378
O
(2008)
22. Merabet-Khelassi M, Aribi-Zouioueche L, Riant
Tetrahedron 20:1371
O
(2009)
23. Merabet-Khelassi M, Houiene Z, Aribi-Zouioueche L, Riant O
(2012) Tetrahedron 23:823
24. Houiene Z, Merabet-Khelassi M, Bouzemi N, Aribi-Zouioueche
L, Riant O (2013) Tetrahedron 24:290
25. Chen CS, Fujimoto Y, Sih CJ (1982) J Am Chem Soc 104:7294
26. Kagan HB, Fiaud JC (1998) Kinetic resolution. In: Eliel EL,
Wilen SH (eds) Topics in stereochemistry, vol 18. Wiley & Sons,
New York, pp 249–330
123