Enantioselective hydrolysis of 1-arylallyl acetates catalyzed by Candida antarctica lipase

Article abstract of DOI:10.1016/j.tetasy.2008.04.018

(R)-1-Arylallyl alcohols were obtained with excellent enantioselectivities via kinetic resolution of the corresponding acetates using immobilized Candida antarctica lipase. The scope and limitations of this reaction were investigated. The best results are obtained using the water/acetonitrile solvent system, and the reaction tolerates a variety of aryl and heteroaryl substituents.

Full text of DOI:10.1016/j.tetasy.2008.04.018

Available online at www.sciencedirect.com
Tetrahedron: Asymmetry 19 (2008) 1053–1058
Enantioselective hydrolysis of 1-arylallyl acetates catalyzed
by Candida antarctica lipase
Ekaterina N. Kadnikova* and Vikalp A. Thakor
Department of Chemistry, University of Missouri-Kansas City, 5100 Rockhill Road, Kansas City, MO 64110, United States
Received 31 December 2007; accepted 2 April 2008
Abstract—(R)-1-Arylallyl alcohols were obtained with excellent enantioselectivities via kinetic resolution of the corresponding acetates
using immobilized Candida antarctica lipase. The scope and limitations of this reaction were investigated. The best results are obtained
using the water/acetonitrile solvent system, and the reaction tolerates a variety of aryl and heteroaryl substituents.
Ó 2008 Elsevier Ltd. All rights reserved.
1. Introduction
alcohols) proved significantly more challenging.12 Only
one resolution of the parent 1-phenylallyl alcohol to the
corresponding acetate was reported, with a moderate
enantioselectivity (81% ee, in a dynamic kinetic resolu-
tion).13 Two other reported examples of kinetic resolution
of 1-phenylallyl alcohol employed oxidation (45% ee)10 or
epoxidation (95% ee) reactions.14
Lipases, obtained from various microorganisms, are the
most widely used enzymes in organic synthesis, mainly
due to their great enantioselectivity.1 They catalyze hydro-
lysis, esterification, trans-esterification, including alcoholy-
sis, and amidation of many substrates. Since enzyme
reactivity, selectivity, and stability in organic solvents is
often worse than that in aqueous solutions, efforts have
been devoted to finding appropriate enzyme formulations
for use in organic media. For example, immobilization of
lipases in or on a solid support enhances their stability,
catalytic activity, and their recyclability.2–4
Herein, we report the first example of preparation of
various enantiomerically-pure (R)-1-arylallyl alcohols via
the lipase-catalyzed kinetic resolution of racemic 1-arylallyl
acetates with very high enantioselectivities (greater than
99%).15
Enantiomerically enriched allylic alcohols and allylic ace-
tates are very useful intermediates in the asymmetric syn-
thesis of more complex molecules.5,6 One of the most
straightforward ways to make these intermediates is enan-
tioselective acylation4,6–8 of secondary allylic alcohols and
enantioselective hydrolysis9 of the corresponding esters cat-
alyzed by enzymes or various non-enzymatic chiral
catalysts.
2. Results and discussion
2.1. Rationale
While the chemoenzymatic approach to many allylic
substrates has historically relied on the enantioselective
conversion of racemic alcohols to chiral acetates via
lipase-catalyzed esterification with acyl donors such as
vinyl acetate,4,16 we envisioned using the reverse process
for our substrates, namely, the enantioselective conversion
of racemic acetates to chiral alcohols via hydrolysis or alco-
holysis in organic solvents or co-solvents. The milder and
more easily tunable conditions of the latter approach are
advantageous for development of other kinetic resolution
regimes, such as chemoenzymatic dynamic kinetic resolu-
tion,9,17 which is the ultimate goal of this project.
While racemic secondary cinnamyl alcohols (1-alkyl-3-aryl-
allyl alcohols) or their acetates have been successfully
resolved using both enzymatic and non-enzymatic chiral
catalysts and reagents,6,7,9–11 kinetic resolution of more
sterically-hindered a-vinylbenzylic alcohols (1-arylallyl
*
Corresponding author. Tel.: +1 816 235 5937; fax: +1 816 235 5502;
e-mail: KadnikovaE@umkc.edu
0957-4166/$ - see front matter Ó 2008 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tetasy.2008.04.018

1054
E. N. Kadnikova, V. A. Thakor / Tetrahedron: Asymmetry 19 (2008) 1053–1058
2.2. Optimization of reaction conditions
In contrast, when C. antarctica lipase B covalently bound
to acrylamide beads (CaL) was used as a catalyst, the same
reaction resulted in excellent yields and enantioselectivities
after 1 day even at a much lower loading of the enzyme
(entries 3 and 4). When this reaction was allowed to run
for six more days, no significant increase in product yield
or decrease in enantioselectivity was observed, indicating
that after the (R)-enantiomer of the starting material is
consumed, the enzymatic hydrolysis is virtually halted.
Thus, CaL catalyzes kinetic resolution (KR) of 1-phenyl-
allyl acetate.
For the initial screening experiments we chose two lipases
known to catalyze the esterification process, reverse to
our hydrolysis, with structurally similar substrates. Can-
dida antarctica lipase B catalyzes the acylation of 1-phenyl-
allyl alcohol,13 while Candida cylindracea lipase (CcL)
catalyzes the acylation of 1-phenyl-2,3-allenol.18 CcL was
immobilized by encapsulation in hydrophobic sol–gel glass,
which was recently shown to improve the reactivity, selec-
tivity, and stability of CcL.3 For the other lipase, a com-
mercially-available immobilized version of the enzyme
(NovozymÒ 435), where the lipase is covalently attached
to acrylamide beads, was employed.
The CaL-catalyzed hydrolysis of this acetate was then
screened in several other acyl acceptor/solvent systems,
such as water or isopropanol (0.25 M or 1:1 (v/v)) in
THF, toluene, or acetone. All systems provided (R)-1-
phenylallyl alcohol in excellent enantioselectivities (>99%
ee, see footnote b in Table 1), but at different rates. Kinetic
resolution (ca. 50% yield of 1-phenylallyl alcohol with ee
>99%) was achieved after one day in water/acetonitrile (en-
tries 3–5) and isopropanol/toluene (entries 9–11) solvent
systems, while in isopropanol/THF (entries 6–8), isopropa-
nol/acetone (entries 12–14), and water/toluene (entries 15–
17) solvent systems it took several days.
Hydrolysis of 1-phenylallyl acetate 1a in water/acetonitrile
solvent system in the presence of C. cylindracea lipase
encapsulated in a hydrophobic sol–gel glass (CcL@glass)
afforded 1-phenylallyl alcohol 1b in low yields and
with low enantioselectivities, even at high catalyst-to-
substrate ratios and longer reaction times (Table 1, entries
1 and 2).
Table 1. Optimization of reaction conditions for the kinetic resolution of
After initial screening, CaL proved to be superior to CcL
for the resolution of 1-phenylallyl alcohol, and the inexpen-
sive and safe water/acetonitrile (1:1) solvent system was
used for further experiments reported here.
1-phenylallyl acetatea
catalyst
Ph
Ph
ROH, solvent
OAc
1a ( )
Entry Catalyst
OH
2a (R)
2.3. Kinetic resolution of various allylic acetates by CaL
ROH and solvent
Time Yieldb eec
After establishing the optimal reaction conditions, we stud-
ied the lipase-catalyzed hydrolysis of various 1-arylallyl
acetates 1 by varying the para-substituent on the phenyl
ring (Table 2, entries 1–6).
(%)
(%)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
CcL@glassd H2O in CH3CNe
8 d
18 d
3 h
1 d
7 d
3 h
1 d
7 d
3 h
1 d
4 d
4 h
1 d
7 d
3 h
1 d
14 d
16
33
33
51
53
2
19
47
20
47
50
13
23
49
32
35
50
24.1
7.7
CaLf
CaLf
CaLf
CaLf
CaLf
H2O in CH3CNe
i-PrOH in THFg
i-PrOH in tolueneg
i-PrOH in acetoneg
H2O in tolueneg
>99
>99
>99
>99
>99
>99
>99
>99
>99
>99
ndh
>99
>99
>99
>99
Substrates with electron-withdrawing substituents 1b–d
(entries 2–4) exhibited a considerably faster rate of hydro-
lysis than the parent unsubstituted substrate (entry 1),
while still maintaining the excellent ee values. Conversely,
a strong electron-donating substituent 1e slowed down
the reaction so much that even after several days only a
minute yield of alcohol was obtained (entry 5). This result
is consistent with the accepted ‘bi bi ping-pong’ mechanism
for C. antarctica lipase B (see Scheme 1),19,20 if the forma-
tion of enzyme-acyl intermediate (so-called acylation step)
is the rate-determining step. In the acylation step, the serine
from the catalytic triad attacks the ester substrate
R0CO2R00, resulting in the subsequent departure of the
alcohol (R00OH) and a formation of enzyme-acyl intermedi-
ate (lipase—O2CR0). Indeed, if acylation is the rate-deter-
mining step, an electron-poor alcohol would be a better
leaving group than an electron-rich alcohol, thus resulting
in faster reaction rates. On the other hand, the rate of the
deacylation step (hydrolysis of enzyme-acyl intermediate)
would be the same for all the substrates in our system.
For CaL, either the acylation or deacylation step could
be rate-determining, depending on the substrates and the
reaction conditions.19,21,22 The acylation becomes the
rate-determining step in our system, because the steric bulk
of the alkoxy part of our esters results in a significant
a (R)-1-phenylallyl alcohol was the predominant enantiomer of the prod-
uct, as concluded from the comparison with an authentic sample.
b Integration error 5–10% for NMR yields.
c An ee value listed as ‘>99’ means that the peak for the opposite enan-
tiomer of the product was not observed; since the relative GC peak area
integration error, as determined from the resolution of racemates, was
0.5–1.0%, then >99% is a conservative estimate.
d Candida cylindracea lipase, immobilized (encapsulated) into hydrophobic
sol–gel silica glass, 1.8 g/ mmol substrate.
e 1:1 (v/v), 0.05 M (0.2 mmol) substrate.
f C. antarctica lipase B, covalently immobilized onto acrylamide beads
(Novozym 435), 0.4 g/ mmol substrate.
g 2.5 M (10 equiv) i-PrOH, 0.25 M (0.2 mmol) substrate.
h Not determined.

E. N. Kadnikova, V. A. Thakor / Tetrahedron: Asymmetry 19 (2008) 1053–1058
1055
Table 2. Kinetic resolution of various allylic acetates
corresponding chiral allylic alcohols 2a
1 into the
bulk of the alkoxy part of the ester led to lower reaction
rates.21
R1
R2
R1
R2
CaL
(R ) for a-h, j, l
(S ) for i, k
( )
1-p-Tolylallyl acetate 1f (entry 6) reacted as fast as 1-phen-
ylallyl acetate 1a (entry 1) but it yielded the only 1-arylallyl
alcohol product, for which a minor enantiomer was
observed; however, the ee value was still very high. Other
aromatic acetates (R1 = 3-pyridyl or 2-naphthyl) were also
efficiently resolved under our optimal conditions, affording
the corresponding alcohols with excellent enantioselectivi-
ties (entries 7 and 8). Overall, with the exception of
1-(4-methoxyphenyl)allyl acetate 1e, a kinetic resolution
of all 1-arylallyl acetates was achieved with excellent
enantioselectivities.
OAc
OH
H2O, CH3CN
1
2
Entry
R1
R2
1
Time Yield of 2b,c eeb,d,e
(h)
(%)
(%)
1
2
3
4
5
6
7
8
9
Ph
H
H
H
H
H
H
H
H
a
b
c
d
e
f
24
51.2 0.7
52.6 0.0f
52.7 0.6g
51.3 0.6
6.1 0.4
53.0 0.2
48.1 0.4
51.2 1.2
51.8 0.6
92.6 0.3
90.0 1.7
66.9 0.2
>99
>99
>99
>99
nd
p-CN–C6H4
p-Cl–C6H4
p-O2N–C6H4
p-CH3O–C6H4
p-CH3–C6H4
3-Pyridyl
2-Naphthyl
CH3
3.0
3.0
3.0
48
24
24
6.0
3.0
24
12
24
96.5 0.1
g
h
i
>99
>99
>99
nd
nd
10.5 0.1
To further examine the scope and limitations of our sys-
tem, the same reaction conditions were also applied to
‘symmetrical’ allylic acetates 1i–j, in which both ends of
the allylic system bear the same substituents, as well as
the simplest secondary allylic acetate 1k and a cyclic sub-
strate 1l (entries 9–12). CaL was very efficient and highly
enantioselective in achieving the kinetic resolution of
pent-3-en-2-yl acetate 1i (entry 9). However, the kinetic res-
olution of 1j–l was not as successful. High yields obtained
in enzymatic hydrolysis of 1j (entry 10) and enzymatic alco-
holysis of acetate 1k (entry 11) indicated that discrimina-
tion between enantiomers may not have occurred in this
case. Enzymatic hydrolysis of 1l (entry 12) proceeds at low-
er rate, but still only low ee was observed.
CH3
Ph
H
10
11h
12
Ph
CH3
j
k
l
–(CH2)3–
a General conditions: 0.05 M (0.2 mmol) substrate, CH3CN/H2O (1:1 v/v),
CaL (0.4 g catalyst/mmol substrate), room temperature (23 °C). See
Section 4 for details on absolute configurations.
b Average of two independent experiments standard deviation.
c Integration error 5–10% for NMR yields. Isolated yields are also
reported for 2b (footnote f) and 2c (footnote g).
d An ee value listed as ‘>99’ means that the peak for the opposite enan-
tiomer of the product was not observed; since the relative GC peak area
integration error, as determined from the resolution of racemates, was
0.5–1.0%, then >99% is a conservative estimate.
e ‘nd’ means not determined.
f In the preparative-scale kinetic resolution of 1b (1.0 mmol scale) the
isolated yield of the product 2b was 49% and the ee was >99%. See
Section 4.8.
3. Conclusion
g In the preparative-scale kinetic resolution of 1c (1.025 mmol scale) the
isolated yield of the product 2c was 48% and the ee was >99%. See
Section 4.8.
In conclusion, C. antarctica lipase B covalently immobi-
lized on acrylamide beads (NovozymÒ 435) catalyzes
hydrolytic kinetic resolution of various readily available
racemic 1-arylallyl acetates, affording enantiomerically-
pure (R)-1-arylallyl alcohols in high yields. The rate of
the reaction depends on the electronic properties of the
substrate, and is faster for electron-poor aryl substituents.
h This alcoholysis reaction was performed in a THF/i-PrOH solvent sys-
tem (2.5 M (10 equiv) i-PrOH, 0.25 M (0.2 mmol) substrate).
O
R''O
A detailed investigation of enantioselective hydrolysis and
alcoholysis reactions of other aryl- and heteroaryl-substi-
tuted allylic acetates, as well as other related unsaturated
substrates, is currently underway. Regimes other than sim-
ple kinetic resolution are also being studied.
R'
OH
OR''
Lipase
Lipase
Lipase
O
OH
R'
O
HO
R''OH
R'
4. Experimental
4.1. Chemicals
OH
OH
Lipase
O
O
O
R'
R'
H2O
All reagents, catalysts, and solvents were obtained from
commercial suppliers and were used without further purifi-
cation, except as noted below. Anhydrous tetrahydrofuran
(THF) was distilled prior to use from sodium benzophe-
none ketyl, or purchased in an inhibitor-free form. Trieth-
ylamine was dried over calcium hydride and then distilled.
Immobilized CcL was prepared by encapsulation into
hydrophobic sol–gel glass as described previously.3 C. ant-
arctica lipase B covalently immobilized on acrylamide
beads (NovozymÒ 435) was obtained from Sigma
Scheme 1. Mechanism of ester hydrolysis catalyzed by Candida antarctica
lipase B.
decrease in the rate of the attack of the serine on the
carbonyl group of the ester. A similar observation was
recently made by Kobayashi, who showed that in his
CaL-based lactone polymerization system acylation was
the rate-determining step, since the increase in the sterical

1056
E. N. Kadnikova, V. A. Thakor / Tetrahedron: Asymmetry 19 (2008) 1053–1058
(L4777). Column chromatography was performed on silica
gel (70–230 mesh, 63–200 lm particle size).
with racemic authentic samples (2a, 2i, 2j, 2k, and 2l) and
previously published data (2b,23 2c,24 2d,25 2e,26 2f,24
2g,27 and 2h28). The absolute configuration of chiral 1-phe-
nylprop-2-en-1-ol (R)-2a was confirmed by comparison
with an authentic sample using a chiral GC analysis. (R)-
Configurations of chiral 1-arylallyl alcohols 2b–h are as-
signed because of their structural analogy to (R)-2a. The
expected configurations of alcohols 2i–l were deduced
using Kazlauskas rule.29
4.2. Instrumentation
1H NMR spectra were recorded at 400 MHz, and 13C
NMR spectra were recorded at 100 MHz, in CDCl3. The
chemical shifts are reported as d values (ppm) relative to
TMS, the integration error was 5–10%. Baseline separation
of enantiomers of allylic alcohols 2a–d, 2f–i, and 2l was
4.4. General procedure for the preparation of allylic
alcohols23
achieved on
a gas chromatograph/mass-spectrometer
(GC–MS) instrument with Chiraldex B-PM column (Astec,
30 m ꢀ 0.25 mm), using helium (99.9995%) as a carrier gas,
a split ratio of 30:1, and an injection volume of 1–3 lL; the
relative GC peak area integration error, as determined
from the resolution of racemates, was 0.5–1%. The various
GC temperature programs for baseline separation are sum-
marized in Table 3, and the retention times for separated
enantiomers of alcohols are shown in Table 4. The solvent
delay for MS acquisition was 5 min.
Aldehyde (3.5 mmol) was dissolved in anhydrous THF
(7.0 mL), and the resulting clear solution was cooled to
ꢁ78 °C. Vinyl magnesium bromide (1.0 M in THF,
4.5 mmol) was then added dropwise to the reaction mixture
at ꢁ78 °C, and the reaction was allowed to slowly warm to
room temperature (23 °C). After 3 h, the reaction mixture
was diluted with diethyl ether and quenched with a satu-
rated NH4Cl solution. The organic layer was separated,
washed twice with water, dried over anhydrous MgSO4,
and concentrated in vacuo. The residual oil was purified
by flash chromatography (silica gel, EtOAc/hexanes) to
yield the corresponding allylic alcohol.
Table 3. GC programs for separation of enantiomers
Program Program Tstart Rate
Tend (°C) Hold time at
Tend (min)
segment
(°C)
(°C/min)
A
B
1
2
3
50
50
90
0
10
5
50
90
200
4
2
25
The following racemic allylic alcohols were previously pre-
pared by the same or similar procedure and characterized
1
2
3
4
5
50
50
90
120
160
0
10
5
2
5
50
90
120
160
200
4
2
4
10
10
1
by at least H NMR and MS: 1-(4-cyanophenyl)prop-2-
en-1-ol 2b,23 1-(4-chlorophenyl)prop-2-en-1-ol 2c,24 1-(4-
nitrophenyl)prop-2-en-1-ol 2d,25 1-(4-methoxyphenyl)-
prop-2-en-1-ol 2e,26 1-(p-tolyl)prop-2-en-1-ol 2f,24 1-(pyri-
din-3-yl)prop-2-en-1-ol 2g,27 and 1-(naphthalen-2-yl)prop-
2-en-1-ol 2h.28
C
1
2
3
4
50
50
90
0
5
2
50
90
150
200
4
2
2
4.5. General procedure for the preparation of allylic
acetates24
150
10
15
D
E
1
2
3
35
35
70
0
1
10
35
70
200
4
4
5
The mixture of allylic alcohol (3.5 mmol), 4-dimethylami-
nopyridine (4.5 mmol), acetic anhydride (4.5 mmol), trieth-
ylamine (4.2 mmol), and methylene chloride (7 mL) was
stirred at room temperature (23 °C) overnight and then
poured into water. The reaction mixture was washed with
2 M HCl, and the aqueous phase was extracted with meth-
ylene chloride. The combined organic extracts were washed
with satd NaHCO3, water, and brine, dried over anhydrous
MgSO4, filtered, and concentrated in vacuo. The residual
oil was purified by flash chromatography (silica gel,
EtOAc/hexanes) to yield the corresponding allylic acetate.
1
2
3
50
50
80
0
2
2
50
80
90
2
2
1
Table 4. Retention times for (R)- and (S)-enantiomers of alcohols
Program
Alcohol
tR (min)
tS (min)
A
1a
1b
1c
1d
1f
18.89
27.19
23.18
30.03
19.99
19.55
27.50
23.62
30.39
20.44
The following allylic acetates were previously prepared by
the same or similar procedure and characterized by at least
1H NMR and MS: 1-(4-chlorophenyl)allyl acetate 1c,24,30
1-(4-methoxyphenyl)allyl acetate 1e,30 1-(p-tolyl)allyl ace-
tate 1f,24,30 1-(4-nitrophenyl)allyl acetate 1d,30 (E)-1,3-
diphenylallyl acetate 1j,31 and cyclohex-2-enyl acetate 1l.32
B
C
D
E
1h
1g
1i
43.48
35.65
20.32
7.75
44.26
36.29
18.50
8.10
1l
Two allylic acetates, 1-(4-cyanophenyl)allyl acetate 1b33
and 1-(naphthalen-2-yl)allyl acetate 1h,34 were previously
reported, but not characterized. 1-(Pyridin-3-yl)allyl ace-
tate 1g has not been reported before. The identity and pur-
ity of these three compounds were confirmed by at least 1H
4.3. Identification of chiral alcohols
The alcohol products were identified by their 1H NMR and
mass-spectra and by GC retention times, in comparison

E. N. Kadnikova, V. A. Thakor / Tetrahedron: Asymmetry 19 (2008) 1053–1058
1057
NMR, 13C NMR, and GC–MS (GC programs used to
check for purity of acetates were the same as the programs
used for enantiomer separation of the corresponding alco-
hols, see Table 3).
described above. Kinetic resolution experiments in this sol-
vent system were performed in duplicates.
4.7.2. Water/toluene. The reaction procedure was the
same as in Section 4.7.1 except that toluene (0.8 mL per
0.2 mmol of substrate) was used as the solvent instead of
acetonitrile and only 10 equiv (2.0 mmol, 0.036 mL) of
water was used.
1-(4-Cyanophenyl)allyl acetate 1b: 1H NMR: d 7.66 (d,
J = 8.4 Hz, 2H), 7.46 (d, J = 8.0 Hz, 2H), 6.26 (d,
J = 6.0 Hz, 1H), 5.90–6.00 (m, 1H), 5.29–5.35 (m, 2H),
2.14 (s, 3H). 13C NMR: d 169.7, 144.0, 135.1, 132.4,
127.6, 118.5, 118.2, 111.9, 75.3, 21.0.
4.7.3. Propan-2-ol/THF. The reaction procedure was the
same as in Section 4.7.1 except that THF (0.8 mL per
0.2 mmol of substrate) was used as the solvent instead of
acetonitrile and 2-propanol (10 equiv, 2.0 mmol,
0.160 mL) was used as the acyl acceptor instead of water.
1
1-(Naphthalen-2-yl)allyl acetate 1h: H NMR: d 7.82–7.88
(m, 4H), 7.45–7.52 (m, 3H), 6.45 (d, J = 5.6 Hz, 1H), 6.06–
6.16 (m, 1H), 5.29–5.40 (m, 2H), 2.16 (s, 3H). 13C NMR: d
169.98, 136.16, 133.10, 133.07, 128.36, 128.03, 127.64,
126.25, 126.23, 124.85, 117.10, 76.26, 21.27 (two aromatic
peaks are missing because of overlaps).
4.7.4. Propan-2-ol/acetone and propan-2-ol/toluene. The
reaction procedure was the same as in Section 4.7.3 except
that acetone or toluene (0.8 mL per 0.2 mmol of substrate)
was used instead of THF.
4.6. Synthesis of 1-(pyridine-3-yl)allyl acetate 1g
A mixture of racemic 1-(pyridine-3-yl)prop-2-en-1-ol (2g,
300 mg, 2.22 mmol), acetic anhydride (0.72 mL), and
DMAP (67.0 mg) was stirred in triethylamine (2.59 mL,
distilled over KOH) for 18 h at room temperature
(23 °C). The clear yellow reaction mixture turned dark
red at the end of the reaction. Methanol (5.0 mL) was
added, and after 20 min the mixture was concentrated in
vacuo. Ether was then added, and the organic phase was
washed with saturated aqueous NaHCO3 and dried over
anhydrous MgSO4. Evaporation of the solvent and purifi-
cation by flash chromatography (80% ethyl acetate in hex-
anes) resulted in the title compound as a yellow oil
(340 mg, 87.2%).
4.7.5. Immobilized C. cylindracea lipase as a catalyst. The
reaction procedure was the same as in Section 4.7.1. except
that C. antarctica lipase B immobilized on acrylic resin
was replaced by C. cylindracea lipase immobilized in
hydrophobic sol–gel glass (180 or 360 mg per 0.2 mmol
of substrate).
4.8. Preparatory-scale kinetic resolutions
For a preparatory-scale kinetic resolution the procedure
for the water/acetonitrile system described above (Section
4.7.1.) was scaled up 5.17 times (1.034 mmol (208 mg) of
substrate 1b, 414 mg of immobilized lipase, 10.3 mL of
acetonitrile, and 10.3 mL of water). After the reaction
was allowed to run for 24 h, immobilized lipase was filtered
off, and the filtrate was extracted with CH2Cl2. The com-
bined organic layers were washed with brine, dried with
anhydrous MgSO4, filtered, and concentrated in vacuo.
Column chromatography on silica gel (2:1 hexanes/ethyl
acetate) yielded 80 mg (0.503 mmol, 49%) of the desired
chiral (R)-1-(4-cyanophenyl)prop-2-en-1-ol 2b as a very
pale yellow oil. In the same experiment, unreacted enantio-
mer of 1b ((S)-1-(4-cyanophenyl)allyl acetate) was also
isolated as a colorless oil (91 mg, 0.454 mmol, 44%).
1H NMR: d 8.62 (d, J = 2.0 Hz, 1H), 8.57 (dd, J = 4.8 Hz,
1.6 Hz, 1H), 7.65 (m, 1H), 7.28 (m, 1H), 6.29 (d,
J = 6.0 Hz, 1H), 5.96–6.05 (m, 1H), 5.29–5.36 (m, 2H),
2.13 (s, 3H). 13C NMR: d 169.8, 149.5, 148.9, 135.3,
134.8, 134.4, 123.4, 117.9, 74.0, 21.1. Anal. Calcd for
C10H11NO2: C, 67.78; H, 6.26; N, 7.90; Found: C,
67.5 0.09; H, 6.21 0.05; N, 8.39 0.09 (average of
two analyses, all elements within 0.4%).
4.7. General procedures for the kinetic resolution experi-
ments in various solvent systems
4.7.1. Water/acetonitrile. Allylic acetate (0.2 mmol), C.
antarctica lipase B immobilized on acrylic resin (Nov-
ozymÒ 435) (80 mg), acetonitrile (2 mL), and water
(2 mL) were mixed in a 15-mL vial and vigorously stirred
at room temperature (23 °C). The progress of the kinetic
Similarly, for the kinetic resolution of 1c the procedure
described in Section 4.7.1 was scaled up 5.125 times
(1.025 mmol (216 mg) of substrate 1c, 410 mg of immo-
bilized lipase, 10.25 mL of acetonitrile, and 10.25 mL of
water), chiral (R)-1-(4-chlorophenyl)prop-2-en-1-ol 2c was
isolated as a colorless oil (83 mg, 0.492 mmol, 48%). In
the same experiment, unreacted enantiomer of 1c ((S)-1-
(4-chlorophenyl)allyl acetate) was also isolated as a slightly
yellow oil (105 mg, 0.486 mmol, 49%).
1
resolution was monitored by H NMR spectroscopy. A
typical procedure for NMR sample preparation involved
withdrawing a small aliquot (40.0 lL) of the reaction mix-
ture, separating lipase from the liquid phase by centrifuga-
tion, extracting the liquid phase with methylene chloride,
drying the combined organic layers with anhydrous
MgSO4, filtering, concentrating in vacuo, and dissolving
in CDCl3 or CD2Cl2. The yield was measured by 1H
NMR spectroscopy (the relative peak area error up to 5–
10%), and the enantiomeric excess was determined by chi-
ral GC–MS (the relative peak area error up to 0.5–1%), as
Isolated chiral compounds were >99.7% pure (by GC,
program A) and were identified as described above (Section
4.3). The ee values were all >99% for isolated (R)-2b,
(S)-1b, (R)-2c, and (S)-1c, as determined by the chiral
GC–MS (see footnote d in Table 2).

1058
E. N. Kadnikova, V. A. Thakor / Tetrahedron: Asymmetry 19 (2008) 1053–1058
15. Kadnikova, E. N.; Thakor, V. A. Abstracts of Papers, 232nd
Acknowledgments
National Meeting of the American Chemical Society, San
Francisco, California, September 10–14, 2006, ORGN-359.
16. Burgess, K.; Jennings, L. D. J. Am. Chem. Soc. 1990, 112,
7434.
17. (a) Choi, Y. K.; Suh, J. H.; Lee, D.; Lim, I. T.; Jung, J. Y.;
Kim, M. J. J. Org. Chem. 1999, 64, 8423; (b) Pamies, O.;
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18. Xu, D. W.; Li, Z. Y.; Ma, S. M. Chin. J. Chem. 2004, 22, 310.
19. Martinelle, M.; Hult, K. Biochim. Biophys. Acta 1995, 1251,
191, Deacylation step is rate-limiting.
We thank our undergraduate research assistants, Tiffany
Coleman, for help with the initial optimization of chiral
GC–MS conditions, and Daniel Yarrow, for synthesis of
some allylic acetates. The financial support of this study
by the University of Missouri—Kansas City and by the
University of Missouri Research Board is gratefully
acknowledged.
20. Raza, S.; Fransson, L.; Hult, K. Protein Sci. 2001, 10, 329.
21. With different substrates, the acylation step can be rate-
limiting, for example: Kobayashi, S. Macromol. Symp. 2006,
240, 178, The increase in the steric bulk of the incoming
nucleophile did not change the rate of the reaction in this
study, thus, deacylation step did not govern the reaction.
22. The nature of the rate-limiting step (deacylation or acylation)
can be concentration-dependent. See, for example: Panova,
A. A.; Kaplan, D. L. Biotechnol. Bioeng. 2003, 84, 103.
23. Fitzpatrick, P. F.; Flory, D. R.; Villafranca, J. J. Biochemistry
1985, 24, 2108.
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