Enzymatic preparation of (1S,2R)- and (1R,2S)-stereoisomers of 2-halocycloalkanols

Article abstract of DOI:10.1016/j.tetasy.2012.11.011

The stereoisomers of cis-2-halocycloalkanols were resolved by a kinetically controlled transesterification with vinyl acetate in the presence of lipases in organic media. High enantioselectivities (ee >98%) and good isolated yields were obtained for all substrates using the appropriate lipase. Burkholderia cepacia lipase was the most efficient enzyme for the resolution of these substrates. The enantiomeric purities of the compounds were defined by derivatization with Mosher's acid and the absolute configurations were determined by chemical correlation.

Full text of DOI:10.1016/j.tetasy.2012.11.011

Tetrahedron: Asymmetry 24 (2013) 37–42
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Tetrahedron: Asymmetry
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Enzymatic preparation of (1S,2R)- and (1R,2S)-stereoisomers
of 2-halocycloalkanols
⇑
Olga O. Kolodiazhna, Anastasy O. Kolodiazhna, Oleg I. Kolodiazhnyi
Institute of Bioorganic Chemistry and Petrochemistry, National Academy of Sciences of Ukraine, Murmanska Str., 1, Kiev, Ukraine
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 16 October 2012
Accepted 19 November 2012
The stereoisomers of cis-2-halocycloalkanols were resolved by a kinetically controlled transesterification
with vinyl acetate in the presence of lipases in organic media. High enantioselectivities (ee >98%) and
good isolated yields were obtained for all substrates using the appropriate lipase. Burkholderia cepacia
lipase was the most efficient enzyme for the resolution of these substrates. The enantiomeric purities
of the compounds were defined by derivatization with Mosher’s acid and the absolute configurations
were determined by chemical correlation.
Ó 2012 Elsevier Ltd. All rights reserved.
1. Introduction
2. Results and discussion
Vicinal halogeno-cycloalkanol derivatives are common building
blocks for a number of chiral natural and synthetic products. These
compounds are important reagents for organic synthesis and are
widely used for the preparation of various biologically active com-
pounds, in particular, prostaglandins and leukotriene precursors.1–
2-Substituted cyclohexanols can be converted into precursors of
prostaglandin F2a, whereas 2-substituted cyclopentanols can be
2.1. Substrate preparation
We have prepared stereoisomers of halogenocycloalkanols by
starting from cycloalkene oxides 1,2.9 The treatment of epoxides
with lithium halogenides led to the formation of racemic, stereo-
chemically pure, trans-2-halogenocycloalkanols 3,4 (Scheme 1).
The racemic trans-2-halogenocyclohexanols 3 were then subjected
to Swern oxidation10a while racemic trans-2-halogencyclopenta-
nols 4 were subjected to Jones oxidation10b to give 2-halogenocy-
cloalkanones 5,6 in good yields. Ketones 5,6 were reduced by
sodium borohydride in methanol to give racemic cis-2-haloge-
nocycloalkanols 7,8. NMR analysis of the reaction mixtures showed
that the cis-2-iodocycloalkanols were formed without trans-isomer
impurities, although the cis-2-fluoro-, 2-chloro- and 2-bro-
mocycloalkanols contained some amount of the trans-isomers
(30%, 12%, and 5%, correspondingly) (Table 1).
The treatment of cis- and trans-2-chlorocycloalkanols with 10%
aq NaOH proceeded with preferable hydrolysis of the trans-isomer
leading to the formation of the pure cis-isomer, which was then
additionally purified by recrystallization from hexane at 0 °C. The
recrystallization of 2-bromocyclohexanol from hexane also yielded
the pure cis-isomer. Analogously the cis-2-bromocyclopentanol
was purified by low-temperature crystallization (at ꢀ30 to
ꢀ40oC) in hexane and obtained as 100% of the cis-isomer. At the
same time, the reduction of 2-fluorocycloalkanols with various
reductants proceeded with low stereoselectivity: sodium borohy-
dride in methanol yielded a mixture of cis- and trans-isomers in
a ratio of 70:30, i-Bu3B in a 75:25 ratio, and i-Bu2AlH (H-DIBAL)
in a 55:45 ratio.
4
converted into L7 leukotriene B4, a conformationally-restricted leu-
kotriene antagonist, used in the enantioselective total synthesis of
(+)-Estron and Desogestrel.5 The (1R,2R)- and (1S,2S)-enantiomers
of trans-halogeno-cyclohexanols and trans-cyclopentanols have
previously been reported on.6–8 Kozma et al.6 performed a one-
pot, solid-state resolution of trans-2-iodocyclohexanol by O,O-
dibenzoyl-(2R,3R)-tartaric acid. Hashimoto,7a,7b Haufe,7c and oth-
ers prepared (1R,2R)-2-chloro-, bromo-, and fluorocyclohexan-1-
ols by the Pseudomonas Fluorescence lipase catalyzed enantioselec-
tive transesterification of 2-substituted cyclohexanols. For this,
Honig8 used the hydrolysis of 2-substituted cyclohexyl butanoates
catalyzed by Candida cylindracea and Pseudomonas sp. Lipases.
However, to date (1R,2S)- and (1S,2R)-stereoisomers of cis-2-halo-
geno-cyclohexanols and cis-2-halogeno-cyclopentanols have not
been resolved and their stereochemical properties have not been
studied. Herein we report a chemoenzymatic approach for the
preparation of the enantiomerically pure stereoisomers of
(1R,2S)- and (1S,2R)-2-halogenocycloalkanols.
The borohydride reductions of 2-substituted cyclohexanones
depended on the conformational equilibrium of the axial and
⇑
Corresponding author. Fax: +38 044 5732552.
E-mail address: olegkol321@rambler.ru (O.I. Kolodiazhnyi).
0957-4166/$ - see front matter Ó 2012 Elsevier Ltd. All rights reserved.
http://dx.doi.org/10.1016/j.tetasy.2012.11.011

38
O. O. Kolodiazhna et al. / Tetrahedron: Asymmetry 24 (2013) 37–42
OH
OH
X
X
X
O
(CH2)n
O
(CH2)n
c,d
b
a
+
X
+
OH
OH
45-65%
65-70%
(CH2)n
1,2
(CH2)n
5, 6a-d
X
(CH2)n
( )-3, ( )-4a-d
n=2 1,3,5,7; 1 2,4,6,8; X=I a, Br b, Cl c, F d
(CH2)n
( )-7, ( )-8a-d
a) LiX/H2O (Cl.Br,I) or Et3N 3HF (X=F); b) DMSO/(COCl)2/Et3N;
c) NaBH4/MeOH; d) 20% NaOH, 20oC, 2hr (X=Cl) or crystallization (X=Br, I)
Scheme 1. Synthesis of the racemic starting compounds.
O-
Table 1
OH
Preparation of racemic cis-2-halogenocycloalkanols
B
O
O
-X-
-H+
Compd
X
n
Reductant/solvent
Yields (%)
cis/trans
X
X
7a
7b
7c
7d
7d
7d
8a
8b
8d
I
2
2
2
2
2
2
1
1
1
NaBH4/MeOH
NaBH4/MeOH
NaBH4/MeOH
NaBH4/MeOH
i-Bu3B/THF
70b
ꢁ100:0
95:5
65b
A
1
3a-c
7a-c
Br
Cl
F
F
F
I
Br
F
70a (35b)
70a
88:12
70:30
75:25
55:45
ꢁ99:1
95:5
50a
O-
OH
X
i-Bu2AlH/toluene
NaBH4/MeOH
NaBH4/MeOH
NaBH4/MeOH
50a
B
-H+
80b
-X-
65b
X
B
70a
70:30
a
Yields for the mixture of the cis- and trans-isomers.
Yields for the purified cis-isomer.
b
B=Base (DBU, RONa, NaOH, i-Pr2NLi)
Scheme 3. Dehydrohalogenation of cis- and trans-2-halogencycloalkanols.
equatorial
attack
O
HO
H
X
X
X
The NMR spectra allowed us to easily define the cis- and trans-
isomers 3,4 and 7,8. For example, in the 1H NMR spectra of the cis-
isomers the signals of the CHX protons are strongly shifted
downfield.
H-
O
cis-7
axial attack
equatorial
conformer
axial conformer
X=F<Cl<Br< I
dr=70:30 (F), 85:15 (Cl),
95:5 (Br), >99:1 (I)
2.2. Enzymatic resolution of 2-hydroxycycloalkanols
Scheme
cyclohexanones.
2. Sodium
borohydride
reduction
of
2-halogen-substituted
In order to obtain enantiomerically pure 2-halohydrins 7,8, we
tested a few lipases with well recognized stereoselective transeste-
rification activity in organic solvents using vinyl acetate (VA) as the
acyl transfer reagent. We tested Candida antarctica (CAL-B), Pseudo-
monas cepacia (PCL), and Burkholderia cepacia (BCL). The best re-
sults (highest ee) were obtained with BCL and therefore used this
lipase.
Enzymatic esterification with vinyl acetate in the presence of
BCL, immobilized on diatomite, allowed us to resolve the racemic
cis-halogencycloalkanols into enantiopure optically active stereo-
isomers. The esterifications were carried out at room temperature
and stopped at 50% conversion into the acetate. In all cases, the
products were obtained with very good enantiomeric excesses
(ee) (Scheme 4 and Table 2).
equatorial forms: equatorial attack of the nucleophile leads to the
formation of trans-alcohols while the axial attack provides the cis-
alcohols.11a–c It has already been shown that the conformational
equilibrium of 2-fluoro-, 2-chloro-, and 2-iodo-cyclohexanones is
shifted toward the axial conformation and that the preference for
the axial position increases with the size of the halogen atom:
F < Cl < Br < I. The axial conformer is the prevailing form for the
chloro- and bromocyclohexanones and is the major form for
iodo-compounds in solvents.11d–f Therefore the conformationally
mobile 2-halogencyclohexanones 5 give rise to the cis-2-halohyd-
rins 7 through the conformation with the 2-substituent in the axial
position (Scheme 2 and Table 1).
The cis-isomers of halogencycloalkanols are more stable toward
hydrolysis than the trans-isomers. Unlike trans-isomers 3, which
upon alkali treatment easily convert into cis-epoxides 1, cis-iso-
mers 7 upon heating with alkali or with excess DBU convert to
cyclohexanone. The cis-orientation of the oxygen and halogen
atoms is unavailable for intramolecular SN2 reaction with the for-
mation of the epoxide. In this case, an alternative anti-conforma-
tion B (via a ring flip) is available for rearrangement via hydride
migration and formation of the cyclohexanone (Scheme 3).
Generally with VA, slow esterifications of 15–18 h with 50%
conversion into acetate 9 were observed. 1H NMR spectroscopy
was used to monitor the progress of the esterification (signal of
CHOH and CHOAc). The enantiomeric purity and ee to the products
of the enzymatic acylation were assigned by preparation of the
Mosher esters with (S)-a-methoxy-a-trifluoromethylphenylacetic
acid chloride [(S)-MTPA-Cl] according to a well established proto-
col.11,12 For (1S,2R)-alcohols 7, the ee (98–99%) of the enzymatic
procedure was established by recording and analyzing the 19F
NMR spectra of the Mosher esters of each enzymatic preparation.

O. O. Kolodiazhna et al. / Tetrahedron: Asymmetry 24 (2013) 37–42
(-)-(1R,2S)-9, 10
39
OH
X
H2O/pH 7.2
BCL
(CH2)n
OAc
(CH2)n
OH
X
OH
OAc
chromatography
(-)-(1R,2S)-7, 8
(CH2)n
+
(CH2)n
BCL
96-98% ee
X
X
( )-cis-7, 8
(1R,2S)-9, 10
(1S,2R)-7, 8
(+)-(1S,2R)-7, 8
98-99% ee
Scheme 4. Enzymatic resolution of cis-2-halogencycloalkanols 7,8.
Table 2
Enzymatic resolution of vicinal halogencycloalkanes 3,4,7,8 through Burkholderia cepacia lipase-catalyzed esterification using vinyl acetate as an acyl donor
Subs-
trate
Conversion
(%)
s
(h)
Alcohol
Recovered alcohol
Acetate
Ea
½
a 2D0
ꢂ
½
a 2D0
ꢂ
½ ꢂ
a 2D0
b
b
Yield
(%)
eeb
(%)
Configuration Yield
(%)
eeb
(%)
Configuration Yield
(%)
eec,d
(%)
Configuration
3a
3b
3c
4a
4b
7a
7b
7c
8a
8b
50
50
50
50
50
51
50
50
52
50
16
16
15
15
15
18
18
16
16
16
45
45
40
45
46
46
45
45
45
45
99
98
97
99
98
>99
99
98
99
99
+33.1 (1S,2S)
+32.0 (1S,2S)
+32.0 (1S,2S)
+33.0 (1S,2S)
+31.3 (1S,2S)
ꢀ31.4 (1S,2R)
ꢀ31.7 (1S,2R)
ꢀ28.0 (1S,2R)
ꢀ31.5 (1S,2R)
ꢀ31.4 (1S,2R)
40
42
40
44
44
40
42
40
40
42
99
99
98
98
98
98
99
96
98
98
ꢀ32.0 (1R,2R)
ꢀ33.0 (1R,2R)
ꢀ30.0 (1R,2R)
ꢀ32.0 (1R,2R)
ꢀ33.2 (1R,2R)
+31.1 (1R,2S)
+31.0 (1R,2S)
+30.0 (1R,2S)
+31.0 (1R,2S)
+30.9 (1R,2S)
45
45
44
48
48
48
44
44
40
48
98
98
96
96
96
98
98
96
98
98
ꢀ68.0 (1R,2R)
ꢀ68.0 (1R,2R)
ꢀ55.0 (1R,2R)
ꢀ52.0 (1R,2R)
ꢀ56.0 (1R,2R)
+62.5 (1R,2S)
+61.0 (1R,2S)
+50.0 (1R,2S)
+62.6 (1R,2S)
+51.0 (1R,2S)
>100
>100
>100
>100
>100
>100
>100
>100
>100
>100
c
Obtained from the NMR spectra of the MTPA esters of the recovered alcohols, which were purified by recrystallization.
a
Calculated by the acylated conversion and % ee of the product. E = ln[1 ꢀ c(1 + eep)]/ln[(1 ꢀ c)(1 ꢀ eep)], where p = product.
b
Determined by the 19F NMR spectra of the respective MTPA esters.
d
[a]
D
and ee were defined for isolated and purified products.
OH
OH
X
OH
X
OAc
X
OAc
(CH2)n
(CH2)n
(CH2)n
(CH2)n
+
lipase
X
(1R,2S)-11, 12
( )-trans-3, 4
(1S,2R)-3, 4
97-99% ee
(1R,2S)-3, 4
98-99% ee
Scheme 5. Enzymatic resolution of trans-2-halogencycloalkanols 3,4.
After column chromatography separation, optically active alco-
ncycloalkanols were colorless low-melting compounds that were
stable at room temperature or in a refrigerator. No racemization
was observed during this work or storage.
hols (+)-(1S,2R)-7 and acetates (ꢀ)-(1R,2S)-9 were obtained with
enantiomeric excesses of 96–99% and with an enantioselectivity
factor of >100.
Acetates 9 were purified by vacuum distillation and then hydro-
lyzed in a phosphate buffer at pH 7.2 in the presence of BCL. Ace-
tates 9,10 were also hydrolyzed by K2CO3 in methanol with the
same ee and yields of hydrolyzed alcohols (1R,2S)-7,8 (Table 2).
From the hydrolysis, enantiomerically pure alcohols (+)-(1S,2R)-
7,8 and (ꢀ)-(1R,2S)-7,8 were obtained. Additional low-temperature
crystallization (at ꢀ20 °C) of the alcohols from hexane allowed us
to obtain alcohols (+)-(1S 2R)-7 and (ꢀ)-(1R, 2S)-9 with de and
ee >99%, which was determined by derivatization of the com-
pounds by Mosher’s acid.11 Acylation of racemic trans-cyclohexa-
nols 3,4 by vinyl acetate in the presence of BCL under kinetically
controlled conditions (50% conversion of initial alcohol) led to
the formation of alcohols (ꢀ)-(1S,2R)-3 and (+)-(1R,2S)-acetates,
which were separated by column chromatography (Scheme 5).
Hydrolysis of the (+)-(1R,2S)-acetate in the phosphate buffer at
pH 7.2 afforded the second stereoisomers of trans-cycloalkanols
(+)-(1R,2S)-3,4 with high enantiomeric purity (98–99% ee, after
recrystallization in hexane). The enantiomerically pure 2-haloge-
2.3. Determination of the absolute configuration
Kazlauskas’ rule12 can be used for assignment of the absolute
stereochemistry of the resolved halogencycloalkanols. Kazlauskas’
rule is a simple empirical model based on the assumption that
enantioselectivity is proportional to the size difference between
the large (L) and medium-size (M) substituents in the substrate.
According to Kazlauskas’ rule, these substituents are located in
two different pockets of the active site of an enzyme, in accordance
with their sizes; this determines the absolute configuration of the
products of the enzymatic reaction. According to Kazlauskas’ rule,
the biocatalytic acetylation of 2-halogencycloalkanols 3,4,7,8
should be (R)-selective (see Fig. 1). Consequently the biocatalytic
transesterification of cycloalkanols should lead to the formation
of (1R,2S)-acetates and (1S,2R)-cycloalkanols.
The absolute configuration of chiral acetates 9,10 was proven by
dehydrohalogenation to give optically active 2-cycloalkenes (R)-
11,12 (Scheme 6).13–15 Heating of the acetates at +70 °C in excess

40
O. O. Kolodiazhna et al. / Tetrahedron: Asymmetry 24 (2013) 37–42
OC(O)CH3
maceutical (Japan). The progress of the reactions and column chro-
OC(O)CH3
matography separation of the resolved products was monitored by
analytical thin layer chromatography (TLC) on pre-coated glass
plates (silica gel 60 F254-plate-Merck, Darmstadt, Germany) and
the products were visualized by anisaldehyde. The purity of all
compounds was verified by thin layer chromatography and NMR
measurements.
(R)
(R)
(R)
(S)
X
X
(CH2)n
(CH2)n
Figure 1. Kazlauskas’ rule for the enantiopreference of BCL toward ( )-3,4 (left) and
( )-7,8 (right).
4.2. Synthesis of racemic compounds
OH
OAc
OAc
Racemic trans-2-chloro-, 2-bromo- and 2-iodocycloalkanols 7,8
were prepared according to earlier described methods, by the reac-
tion of cyclohexene oxide or cyclopentene oxide with lithium
halogenides.9,17 Trans-2-fluorocyclohexanol and trans-2-fluorocy-
clopentanol were prepared by the reaction of cycloalkene oxides
with triethylamine trihydrofluoride.18
DBU
[-HI]
NaOH/H2O
n=2
X
(CH)n
(1R,2S)-
(CH)n
13,14
15
(R)-
9,10
(R)-
n=2 13, n = 1 14
4.2.1. Synthesis of racemic cis-halogencycloalkanols rac-7,8
Racemic cis-halogencycloalkanols were prepared by reduction
of 2-halogencycloalkanones with sodium borohydride in methanol
as described below.19–21 The 1H and 13C NMR spectra allowed us to
determine between the cis- and trans-isomers.
Scheme 6. Correlation of compounds 9,10a–c with the 2-cycloalkenyl acetates
13,14.
DBU for several hours led to the formation of enantiomerically
pure cycloalkenyl acetates (+)-(R)-13,14 in good yields, which were
purified by vacuum distillation. The hydrolysis of (R)-13 with 20%
aq NaOH furnished (R)-cyclohexenol 15.8 The absolute configura-
tion of compound (R)-14 was assigned by comparison with the
specific rotation of the known cyclopentenyl acetates.13–16 From
the absolute configuration of (R)-13 and (R)-14, we were able to
determine the absolute configuration of 2-halogencycloalkanols
7,8 by chemical correlation. Thereby, the biocatalytic esterification
of racemic 2-cycloalkanols by vinyl acetate proceeded in accor-
dance with Kazlauskas’ rule.
4.2.1.1. (a) Preparation of 2-halogencycloalkanone.
To a
solution of oxalyl chloride (2.9 g, 23 mmol) in 40 ml of methylene
chloride were added dropwise 3.6 ml (50 mmol) of DMSO in 10 ml
of methylene chloride at ꢀ70 °C. The trans-2-halogencycloalkanol
(20 mmol) was added and the reaction mixture was stirred for
20 min. The temperature was then raised to ꢀ55 °C and 16 ml of
triethylamine was added. The reaction mixture was stirred for
20 min, warmed to 0 °C, and poured into a 1 M hydrochloric acid
solution. The water phase was separated and extracted with meth-
ylene chloride, the combined organic phases were washed with
water, dried over anhydrous sodium sulfate, and concentrated un-
der reduced pressure. The residue was distilled under vacuum. rac-
5a: yield 65%, bp 110 °C (10 mmHg).22a 1H NMR (500 MHz, CDCl3):
d 1.40 (m, 1H, CH2), 1.60 (m, 2H, CH2), 1.90 (m, 1H, CH2), 2.10–2.31
(m, 2H, CH2), 2.45 (m, 2H, CH2), 5.21 (m, 1H, CHI). rac-5d: yield
45%, bp 70 °C (10 mmHg).22b rac-6a: yield 65%, bp 100 °C
(10 mmHg).22c rac-5b, rac-5c, rac-6b;22c were prepared by known
methods.
(b) To halogencycloalkanones 5,6 (10 mmol) in 50 ml of metha-
nol was added sodium borohydride (0.12 mol) at 0 °C and the reac-
tion mixture was stirred for 2 h at room temperature. Next, NH4Cl
(11 mmol) was added and the reaction mixture was stirred for
0.5 h, filtered off, evaporated under reduced pressure, and the res-
idue was extracted with methylene chloride. The extract was then
dried over Na2SO4. The solvent was removed under reduced pres-
sure and the residue was recrystallized from hexane. Spectroscopic
data of 7b–d; 8b,c were in accordance with literature data.20–22
rac-7a. Yield 70%, mp 52–53 °C (hexane). 1H NMR (500 MHz,
CDCl3): d 1.45 (m, 2H, CH2), 1.45–1.80 (m, 4H, CH2), 1.19 (m, 2H,
CH2), 2.27 (m, 1H, OH), 3.16 (m, 1H, CHI), 4.71 (s, 1H, CHOH). 13C
NMR (125.74 MHz, CDCl3): d 21.93 (s, CH2), 24.48 (s, CH2), 32.23
(s, CH2), 34.12 (s, CH2), 46.51 (s, CHI), 71.01 (s, CHOH). Found
(%): C, 31.38; H, 4.50. C6H11IO. Calculated (%): C, 31.88; H, 4.90.
rac-7b. Yield: 65%, bp 115 °C (12 mmHg). Mixture of cis- and
trans-isomers 7b and 3b in ratio of 95:5. After crystallization in
hexane at ꢀ20 °C the product was obtained as a pure cis-isomer
of rac-7b. Colorless prisms. Mp 34 °C. (lit.20,21, oil, bp 69 °C/
14 mmHg) mixture of cis- and trans-isomers)
3. Conclusion
In conclusion, enantiomerically pure (1R,2S)- and (1S,2R)-2-
halogencycloalkanols were prepared via biocatalyzed kinetic reso-
lution in good yields and with high enantiomeric excess. Burk-
holderia cepacia lipase showed excellent enantioselectivity as a
biocatalyst for the transesterification of cyclohexanols with vinyl
acetate. The absolute configuration of enantiomerically pure 2-
halogencycloalkanols was determined by chemical correlation
with known compounds. The biocatalytic esterification of 2-cyclo-
alkanols with vinyl acetate proceeded in accordance with Kazlaus-
kas’ rule. In contrast to the chemo-catalyzed multi-step synthesis
of chiral cyclic 2-halohydrins, the present methodology is straight-
forward, and uses commercially available lipases.
4. Experimental
4.1. General
1H NMR and 13C NMR spectra were recorded in a CDCl3 solvent
on a 500 MHz spectrometer at ambient temperature. Chemical
shifts (d) are reported in ppm on a scale downfield from TMS as
the internal standard. Signal patterns are as follows: s, singlet; d,
doublet; dd, doublet of doublet; td, triplet of doublet; t, triplet;
m, multiplet; br s, broad singlet. Coupling constants J are in Hertz.
All reagents and solvents were reagent grade and used without fur-
ther purification unless specified otherwise. Column chromatogra-
phy was performed on Silica Gel 60 (70–230 mesh) using the
specified eluents. Optical rotations were measured on a Perkin-El-
mer 241 polarimeter (sodium D line at 20 °C). Melting points are
uncorrected. All reactions were performed in flame-dried or
oven-dried glassware with magnetic stirring. Lipase from
Burkholderia cepacia (Amano PS) was purchased from Amano Phar-
rac-7c. The product was obtained as a mixture of cis- and trans-
isomers 7c and 3c. The mixture of 3c and 7c was treated with 1 M
sodium hydroxide for 1.5 h at room temperature. The product was
extracted with methylene chloride. The solvent was then evapo-
rated. 1H and 13C NMR analyses of the residue showed the presence

O. O. Kolodiazhna et al. / Tetrahedron: Asymmetry 24 (2013) 37–42
41
of cis-2-chlorocyclohexanol 7c, cyclohexene epoxide, cyclohexa-
none, and only trace amounts (ꢁ1%) of the trans-isomer 3c. The
residue was then distilled under vacuum, bp 70 °C (12 mmHg).
After recrystallization from hexane the product was obtained as
pure cis-3c. Yield 35%, colorless prisms, mp 30 °C (hexane,
ꢀ20 °C), [lit. oil, bp 75 °C (8 mmHg), mixture of cis + trans-
isomers].21
at a constant pH value of 7.2 using BCL as a biocatalyst (0.2 g) with
stirring and room temperature. The hydrolysis was monitored by
TLC analysis and 1H NMR. The lipase was then filtered off and
washed out with methylene chloride. The solvent was removed
and the residue was extracted with ethyl acetate. The extract
was evaporated and the residue was recrystallized from hexane
to afford the recovered alcohol. Yield 60% (28% from starting rac-
rac-7d. Yield 70%, bp 60 °C (12 mmHg). 1H NMR (500 MHz,
CDCl3): d 1.25–1.35 (m, 2H, CH2), 1.5–1.70 (m, 5H, CH2CH2), 2.0–
2.1 (m, 1 H, CH2), 2.4 (br, 1 H, OH), 3.78 (d, 1H, J = 5, CHOH), 4.69
(dd, JH,F = 40 Hz, J = 3 Hz, 1 H, CHF), 13C NMR (125.74 MHz, CDCl3):
20.90 s, 22.00 s, 28.50 s, 30.10 s, 70.0 s, 92.87.21,23
7a), mp 50 °C (hexane), ½a D20
ꢂ
¼ þ31:1 (c 1, CHCl3). 1H and 13C
NMR spectra are similar to those of (1S,2R)-7a.
4.3.3. Resolution of cis-2-bromocyclohexanol 7b
4.3.3.1. (ꢀ)-2-Bromocyclohexanol (1S,2R)-7b.
Yield 45%, mp
rac-8a. Yield 80%, bp 70 °C (12 mmHg). 1H NMR (500 MHz,
CDCl3) d: 1.61–1.54 (m, 1H), 1.84–1.78 (m, 2H), 2.15–2.01 (m,
2H), 2.39–2.32 (m, 1H), 4.05–4.01 (m, 1H), 4.45–4.42 (m, 1H). 13C
NMR (125.74 MHz, CDCl3): d 21.51 s, 23.31 s, 30.28 s, 34.63 s,
74.96 s. Found (%): C, 28.38; H, 4.50. C5H9IO. Calculated (%): C,
28.32; H, 4.28.
32–34 °C, ½a 2D0
ꢂ
¼ ꢀ31:7 (c 1, CHCl3). 1H NMR (500 MHz, CDCl3): d
1.55–1.65 (3H, m), 1.75–1.85 (3H, m), 1.9–2.1 (1H, m), 2.15–25
(1H, m), 4.02 (1H, m), 4.32 (1H, m). 13C NMR (125.74 MHz, CDCl3):
d 24.3 s, 26.7 s, 33.8 s, 36.4 s, 61.9 s, 75.5 s. Calculated: C 40.25; H
6.19; Br 44.63 for C6H11 BrO. Found: C 40.25; H 6.19; Br 44.63.
rac-8b. Yield 65%, ꢁ100% de, mp ꢁ0 °C (hexane, ꢀ50 °C) (lit.20
mixture of cis + trans-isomers).
4.3.3.2. (+)-2-Bromocyclohexyl acetate (1R,2S)-9b.
Yield
42%, bp 45 °C (0.1 mmHg). ½a D20
¼ þ61:0 (c 5, CHCl3). Rf 0.36
ꢂ
rac-8d. Yield of 70%. Bp 50 °C (12 mm Hg). lit.21 mixture of
cis + trans-isomers).
(CHCl3). 1H NMR (500 MHz, CDCl3): d 1.4–1.5 (m, 2H), 1.6–1.8
(3H, m, CH2), 1.8–1.9 (2H, m, CH2), 2.27 (3H, s, CH3CO), 4.5 (1H,
s, CHBr), 4.72 (1H, s, CHOAc). 13C NMR (125.74 MHz, CDCl3): d
22.06 s, 22.20 s, 28.06 s, 32.86 s, 34.35 s, 72.48 s, 170.02 s.
The preparation of pure cis-2-fluorocycloalkanols 7d, 8d and
their resolution into enantiomers is currently underway.
4.3. Lipase-mediated resolution of racemic 2-
halogencycloalkanols
4.3.3.3. (+)-2-Bromocyclohexanol (1R,2S)-7b.
Yield 42%, mp
32–34, ½a 2D0
¼ þ31:0 (c 1, CHCl3).
ꢂ
4.3.1. General procedure
4.3.4. Resolution of cis-2-chlorocyclohexanol 7c
4.3.4.1. (ꢀ)-2-Chlorocyclohexanol (1S,2R)-7c.
A solution of suitable 2-halogencycloalkanol (20 mmol), lipase
(0.3 g), vinyl acetate, (10 ml) and t-BuOMe (10 ml) was stirred at
+24 °C and the formation of the acetylated compounds was moni-
tored by TLC and NMR analyses. The reaction mixture was stirred
up to 50% conversion of the starting alcohol. The reaction mixture
was filtered, concentrated under vacuum, and the resulting oil was
purified by chromatography on silica gel using hexane–ethyl ace-
tate (95:5–3:1) as eluent. Alcohols were additionally recrystallized
in hexane. Acetates were distilled under vacuum.
Acetates 9,10 (10 mmol) were hydrolyzed by K2CO3 (2 g) in
20 ml of methanol with stirring at room temperature. The hydroly-
sis was monitored by TLC analysis. The solvent was removed and
the residue was extracted with ethyl acetate. The extract was then
evaporated and the residue was crystallized from hexane to afford
the recovered alcohol. The 2-iodocyclohexyl acetate (1R,2S)-9a was
also hydrolyzed in a phosphate buffered water solution using BCL
and then recrystallized from hexane (See below).
Yield 45%, mp
ꢂ
38 °C (hexane, ꢀ20 °C), bp 76–83 °C (13 mmHg) ½a D20
¼ ꢀ28 (c 1,
CHCl3). 1H NMR (500 MHz, CDCl3): d 1.25–1.44 (3H, m), 1.6–1.88
(3H, m), 2.15 (1H, m), 2.35 (1H, m), 2.58 (1H, s), 3.62 (1H, m),
3.92 (1H, m). 13C NMR (125.74 MHz, CDCl3): d 24.1 s, 25.8 s, 33.6
s, 35.3 s, 67.5 s, 75.5 s.
4.3.4.2. (+)-2-Chlorocyclohexyl acetate (1R,2S)-9c.
Yield
44%, colorless oil, bp (10 mmHg), Rf 0.45 (CHCl3), ½a D20
ꢂ
¼ þ50:0 (c
5, CHCl3). 1H NMR (CDCl3–500 MHz): d 1.44–1.55 (2H, m), 1.65–
1.8 (3H, m), 1.85–2.0 (2H, m), 2.15 (3H, s), 4.5 (1H, m), 4.85 (1H,
m). 13C NMR (125.74 MHz, CDCl3): d 20.84 s, 21.23 s, 27.24 s,
32.25 s, 38.73 s, 60.48 s, 72.63 s, 170.34 s.
4.3.4.3. (+)-2-Chlorocyclohexanol (1R,2S)-7c.
Yield 40%, col-
orless prisms, mp 36 °C (hexane, ꢀ20 °C). ½a D20
ꢂ
¼ þ30 (c 1, CHCl3).
4.3.5. Resolution of cis-2-iodocyclopentanol 8a
4.3.5.1. (ꢀ)-2-Iodocyclopentanol (1S,2R)-8a.
4.3.2. Resolution of cis-2-iodocyclohexanol 7a
Yield 45%, mp
4.3.2.1. (ꢀ)-2-Iodocyclohexanol (1S,2R)-7a.
Yield 46%, mp
ꢁ0 °C. ½a 2D0
ꢂ
¼ ꢀ31:5 (c 1, CHCl3). 1H NMR (500 MHz, CDCl3): d
52–53 °C (hexane), ½a D20
ꢂ
¼ ꢀ31:4 (c 1, CHCl3). 1H NMR (500 MHz,
1.61–1.54 (1H, m), 1.84–1.78 (2H, m), 2.15–2.01 (2H, m), 2.39–
2.32 (1H, m), 4.05–4.01 (1H, m), 4.45–4.42 (1H, m). 13C NMR (CDCl3,
125.74 MHz): d 21.51 s, 23.31 s, 30.28 s, 34.63 s, 74.96 s. Calculated
(%): C, 28.32; H, 4.28 for C5H9IO. Found (%): C, 28.38; H, 4.50.
CDCl3): d 1.45 (m, 2H, CH2), 1.45–1.80 (m, 4H, CH2), 1.19 (m, 2H,
CH2), 2.27 (m, 1H, OH), 3.16 (m, 1H, CHI), 4.71 (s, 1H, CHOH). 13C
NMR (125.74 MHz, CDCl3): d 21.93 s, 24.48 s, 32.23 s, 34.12 s,
46.51 s, 71.01 s. Calculated (%): C, 31.88; H, 4.90. C6H11IO. Found
(%): C, 31.38; H, 4.50.
4.3.5.2. (+)-2-Iodocyclopentyl acetate (1R,2S)-10a.
Yield
40%, ½a 2D0
ꢂ
¼ þ62:6 (c 1, CHCl3). 1H NMR (500 MHz, CDCl3): d
4.3.2.2. (+)-2-Iodocyclohexyl acetate (1R,2S)-9a.
Yield 48%,
1.30–1.40 (2H, m, CH2), 1.7–1.8 (2H, m, CH2), 1.9 (1H, m, CH2),
2.10 (3H, m, CH3), 4.1 (1H, m, CHBr), 5.20 (1H, m, CHOAc).
bp 115 °C (10 mmHg),
½
a 2D0
ꢂ
¼ þ62:5 (c 3, CHCl3). 1H NMR
(500 MHz, CDCl3): d 1.40–1.65 (m, 4H, CH2), 1.85 (m, 1H, CH2),
2.00–2.10 (m, 4H, CH2), 2.15 (s, 3H, CH3), 2.45 (m, 1H, OH), 4.05
(m, 1H, CHI), 4.95 (m, 1H, CHOAc). 13C NMR (125.74 MHz, CDCl3): d
21.30s, 22.40s, 23.77s, 29.30s, 34.44s, 36.04s, 72.95s, 170.16s. Cal-
culated (%): C, 35.84; H, 4.89. C8H13IO2. Found (%): C, 35.68; H, 4.71.
4.3.5.3. (+)-2-Iodocyclopentanol (1R,2S)-8a.
orless oil at room temperature, mp ꢁ0 °C (hexane, ꢀ20 °C),
¼ þ31:0 (c 1, CHCl3).
Yield 42%, col-
½ ꢂ
a 2D0
4.3.6. Resolution of cis-2-bromocyclopentanol 8b
4.3.6.1. (ꢀ)-2-Bromocyclopentanol (1S,2R)-8b.
4.3.2.3. (+)-2-Iodocyclohexanol (1R,2S)-7a.
(5 mmol) was hydrolyzed in a phosphate buffered water solution
Acetate 9a
Yield 45%,
mp ꢁ0 °C, ½a 2D0
ꢂ
¼ ꢀ31:4 (c 1, CHCl3). 1H NMR (500 MHz, CDCl3): d

42
O. O. Kolodiazhna et al. / Tetrahedron: Asymmetry 24 (2013) 37–42
1.45 (m, 2H, CH2), 1.45–1.80 (m, 4H, CH2), 1.19 (m, 2H, CH2), 2.27
(m, 1H, OH), 3.16 (m, 1H, CHI), 4.71 (s, 1H, CHOH). 13C NMR
(125.74 MHz, CDCl3): d 21.93 s, 24.48 s, 32.23 s, 34.12 s, 46.51 s,
71.01 s.
4.5.1.2. 2-Cyclopentenyl acetate (R)-14.
The evaporation in
vacuo should be carried out with caution because of the volatility
of the product. The 2-cyclopentenyl acetate was purified by flash
chromatography (pentane–ether). Colorless oil. Yield 25%,
½
a 2D0
ꢂ
¼ þ170 (c 1, CHC13) {lit.24a
½
a 2D0
ꢂ
¼ ꢀ83:8 (c 1.09, CH2C12),
4.3.6.2. (+)-2-Bromocyclopentyl acetate (1R,2S)-10b.
Yield
41% ee for the (S)-absolute configuration}. 1H NMR (500 MHz,
CDCl3): d 6.09–6.07 (1H, m), 5.81–5.79 (1H, m), 5.68–5.65 (1H,
m), 2.52–2.47 (1H, m), 2.31–2.23 (2H, m,), 2.01 (3H, s,), 1.81–
1.75 (1H, m,). 13C NMR (125.74 MHz, CDCl3): d 170.9, 137.5,
129.1, 80.4, 30.9, 29.6, 21.2.
42%,
½
a 2D0
ꢂ
¼ þ51:0 (c 1, CHCl3), Rf 0.36 (CHCl3). 1H NMR
(500 MHz, CDCl3): d 1.3–1.45 m (2H, CH2), 1.55–1.7 m (2H, CH2),
1.8–2.0 m (2H,CH2), 2.12 s (3H, CH3), 4.46 m (1H, CHBr), 4.97 m
(1H CHOAc). 13C NMR (125.74 MHz, CDCl3): d 19.75 s, 20.92 s,
27.77 s, 33.50 s, 53.12 s, 75.70 s, 170.4 s.
4.5.1.3. 2-Cyclohexen-1-ol (R)-15.
To a solution of 2-cyclo-
4.3.6.3. (+)-2-Bromocyclopentanol (1R,2S)-8b.
Yield 40%,
hexenyl acetate (R)-13 (1.1 g, 8.0 mmol) in 1.5 ml of methanol
was added a solution of NaOH (1 M, 15 ml). The mixture was stir-
red overnight at room temperature. The mixture was then ex-
tracted with methylene chloride. The extract was evaporated and
the residue was distilled under vacuum. Yield 0.60 g (80%), color-
mp <0, ½a 2D0
¼ þ30:9 (c 1, CHCl3).
ꢂ
4.3.7. Resolution of trans-2-halogencycloalkanols 3a–c
We carried out the biocatalytic kinetic resolution of trans-2-
halogencyclohexanols with vinyl acetate in the presence of BCL.
The resolution of these compounds was performed by biocatalytic
hydrolysis of the acetates in the presence of Candida cylindracea li-
pase, Pseudomonas sp. lipase, and also by trans-esterification with
vinyl acetate catalyzed by Pseudomonas fluorescencia lipase 7,8. It
was necessary for us to compare the results of the resolution for
the cis- and trans-2-halogeno–hydrins under the same conditions.
The results can be seen in Table 2. The data in Table 2 clearly show
that the biocatalytic resolution of cis- and trans-2-halogenhydrins
follows Kazlauskas’ rule.
less oil, bp 96–97 °C (75 mmHg), ½a D20
ꢂ
¼ þ123:5 (c 2, CHCl3). 1H
NMR (500 MHz, CDCl3): d 2.11–1.39 (7H, m), 4.29–4.03 (1H, m,
CHOH), 5.97–5.58 (2H, m, CH@).24b
Acknowledgments
This work was financially supported by the State Foundation for
Basic Research of Ukraine and the Russian Foundation for Basic Re-
search (joint Project No. F40.3/034).
References
4.4. Determination of the enantiomeric purity of the
compounds
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The enantiomeric excesses of the compounds were determined
by the formation of the Mosher esters of (S)-
luoromethylphenylacetyl chloride [(S)-MTPA-Cl] with haloge-
ncycloalkanols: to solution of an alcohol (0.1 mmol) and
a-methoxy-a-trif-
a
pyridine (0.2 mmol) in 0.5 ml of absolute THF was added a solution
of MTPA-Cl (26 mg, 0.11 mmol) in 0.5 ml of THF at ꢀ70 °C. The
temperature was increased to room temperature and the reaction
mixture was centrifuged. The centrifugate was analyzed by 19F
NMR and 1H NMR spectra. Two signals were discovered in racemic
alcohols at ꢀ71–72 ppm (19F) and 3.55–3.60 ppm (1H, MeO-group)
and only one signal was present in the kinetically resolved
alcohols.
4.5. Determination of the absolute configuration of 2-
halogencycloalkenols 7,8
The absolute configuration of the compounds was assigned by
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and cyclopentenol as described below.
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4.5.1.1. 2-Cyclohexenyl acetate (R)-13.
A mixture of (+)-
(1R,2S)-2-iodo- or bromocyclohexyl acetate 9a,b (2 g) and DBU
(5 ml) was heated for 12 h at 70 °C, then the reaction mixture
was diluted with ether, filtered, and washed with dilute hydrochlo-
ric acid and an aqueous solution of sodium bicarbonate. The sol-
vent was evaporated under reduced pressure and the residue
was purified by column chromatography and bulb to bulb distilla-
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60 °C (10 mmHg). ½a D20
ꢂ
¼ þ180 (c 3, CHCl3).7b 1H NMR (500 MHz,
CDCl3): d 2.02 (3H, s, CH3), 2.29–1.63 (6H, m, CH2), 5.73–5.67
(1H, m, OH), 5.99–5.92 (1H, m, CH@), 5.28–5.23 (1H, m, CH@).