Synthesis of optically active vicinal fluorohydrins by lipase-catalyzed deracemization

Article abstract of DOI:10.1021/jo016331r

Three microbial lipases have been used to deracemize trans-2-fluorocycloalkanols 2 both by hydrolysis of the corresponding acetates 3 or chloroacetates 4 and by esterification of the fluorohydrins 2 using vinyl acetate and vinyl chloroacetate, respectivel

Full text of DOI:10.1021/jo016331r

J . Org. Chem. 2002, 67, 3015-3021
3015
Syn th esis of Op tica lly Active Vicin a l F lu or oh yd r in s by
Lip a se-Ca ta lyzed Der a cem iza tion
D o¨ rthe W o¨ lker and G u¨ nter Haufe*
Organisch-Chemisches Institut, Westf a¨ lische Wilhelms-Universit a¨ t M u¨ nster,
Corrensstr. 40, D-48149 M u¨ nster, Germany
haufe@uni-muenster.de
Received November 29, 2001
Three microbial lipases have been used to deracemize trans-2-fluorocycloalkanols 2 both by
hydrolysis of the corresponding acetates 3 or chloroacetates 4 and by esterification of the
fluorohydrins 2 using vinyl acetate and vinyl chloroacetate, respectively. Pseudomonas cepacia lipase
was the most selective for the six- and the seven-membered-ring compounds, while the lipase from
Candida rugosa was most useful for the eight-membered-ring compounds. Both lipases transform
the (R)-enantiomers preferrentially. In contrast the lipase from Candida antarctica hydrolyzed
the esters of trans-2-fluorocyclohexanol 2a and esterified the fluorohydrin itself with very low
enantiopreference for the (R)-isomers. The seven- and the eight-membered ring esters and the
corresponding fluorohydrins were also transformed with low, but reverse, enantioselectivity.
In tr od u ction
activated olefinic double bonds, and deracemization or
desymmetrization of fluorinated esters. Enantiomeri-
8
Synthesis of optically active fluorinated compounds
exhibiting biological activity or useful properties with
respect to new materials has found considerable attention
cally enriched fluorinated carboxylic acids have mostly
been synthesized by lipase-catalyzed hydrolysis of the
9
corresponding esters. There are also some examples of
1
during the past several years. However, there are only
enantioselective esterifications of carboxylic acids or
a few methods of enantioselective syntheses of such
compounds from achiral or racemic precursors. Until
recently, asymmetric carbon-carbon bond formation of
10
transesterifications of esters. Optically active fluori-
nated alcohols have been obtained analogously. Two
alternative pathways have been employed, namely hy-
2
fluorinated building blocks or asymmetric reduction of
11
drolysis of â-fluoroalkyl esters or acylation of vicinal
3
fluorinated carbonyl compounds were two known strate-
12
fluorohydrins.
gies for synthesizing optically active fluorinated com-
pounds. The only direct method of synthesis was asym-
metric electrophilic fluorination using either enantio-
merically pure N-fluoro compounds or catalytic enan-
tiopure metal complexes in combination with Select-
fluor.4 Our discovery of the first efficient asymmetric
introduction of fluoride anion by Lewis acid mediated ring
opening of meso or racemic epoxides added another tool
for chiral organofluorine chemistry.7
In connection with our ongoing research13 on the regio-
and stereochemistry of microbiological hydroxylation and
the influence of fluorine atoms on the selectivity of such
(
4) Differding, E.; Lang, W. R. Tetrahedron Lett. 1988, 29, 6087-
6090. (b) Davis, F. A.; Zhou, P.; Murphy, C. K. Tetrahedron Lett. 1993,
4, 3971-3974. (c) Takeuchi, Y.; Suzuki, T.; Kameda, A.; Dohrin, M.;
-6
3
Satoh, T.; Koizumi, T.; Kirk, K. L. Chem. Pharm. Bull. 1997, 45, 1085-
1088. (d) Davis, F. A. Zhou, P.; Murphy, C. K.; Sundarababu, G. Qi,
H.; Han, W.; Przeslawski, R. M.; Chen, B.-C.; Carroll, P. J . J . Org.
Chem. 1998, 63, 2273-2280. (e) Takeuchi, Y.; Suzuki, T.; Satoh, T.;
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Takeuchi, Y. Tarui, T.; Shibata, N. Org. Lett. 2000, 2, 639-642. (g)
Shibata, N.; Suzuki, E.; Takeuchi, Y. J . Am. Chem. Soc. 2000, 122,
Optically active organofluorine compounds have also
been prepared by enzymatic methods such as yeast
reductions of fluorinated ketones, hydrogenations of
1
0728-10729. (h) Cahard, D.; Audouard, C.; Plaquevent, J .-P.; Roques,
N. Org. Lett. 2000, 2, 3699-3701.
*
To whom correspondence should be addressed. Fax: +49-251-83-
9772.
1) (a) Enantiocontrolled Synthesis of Fluoro-organic Compounds.
Stereochemical Challenges and Biomedicinal Targets; Soloshonok, V.
A., Ed.; J ohn Wiley Sons: Chichester, 1999. (b) Asymmetric
Fluoroorganic Chemistry. Synthesis, Applications, and Future Direc-
tions; Ramachandran, P. V., Ed.; ACS Symposium Series 746; Ameri-
can Chemical Society: Washington, 2000.
(5) Hintermann, L.; Togni, A. Angew. Chem. 2000, 112, 4530-4533;
Angew. Chem., Int. Ed. 2000, 39, 4359-4362.
3
(
(6) For recent reviews cf. (a) Mu n˜ iz, K. Angew. Chem. 2001, 113,
1701-1704; Angew. Chem., Int. Ed. 2001, 40, 1653-1656. (b) Davis,
F. A.; Qi, H.; Sundarababu, G. In ref 1a, pp 1-32.
&
(7) (a) Bruns, S.; Haufe, G. J . Fluorine Chem. 2000, 104, 247-254.
(b) Haufe, G.; Bruns, S. Adv. Synth. Catal. 2002, in press.
(8) Fujisawa, T.; Shimizu, M. In ref 1a, pp 307-348.
(
2) (a) Iseki, K. In ref 1a, pp 33-62; in ref 1b, pp 38-51. (b) Bravo,
(9) (a) Kitazume, T.; Sato, T.; Ishikawa, N. Chem. Lett. 1984, 1811-
1814. (b) Kitazume, T.; Murata, K.; Ikeda, T. J . Fluorine Chem. 1986,
31, 143-150. (c) Kalaritis, P.; Renenye, R. W.; Partridge, J . J .; Coffen,
D. L. J . Org. Chem. 1990, 55, 812-815. (d) Dasaradhi, L.; O’Hagan,
D. Bioorg. Med. Chem. Lett. 1993, 3, 1655-1658. (e) O’Hagan, D.;
Rzepa, H. S. J . Chem. Soc., Perkin Trans. 2 1994, 3-4. (f) Yamazaki,
Y.; Yusa, S.; Kageyama, Y.-I.; Tsue, H.; Hirao, K.-I.; Okuno, H. J .
Fluorine Chem. 1996, 79, 167-171. (g) Kometani, T.; Isobe, T.; Goto,
M.; Takeuchi, Y.; Haufe, G. J . Mol. Catal. B, Enz. 1998, 5, 171-174.
(h) Takeuchi, Y.; Konishi, M.; Hori, H.; Takahashi, T.; Kometani, T.;
Kirk, K. L. Chem. Commun. 1998, 365-366. (h) Narisano, E.; Riva,
R. Tetrahedron: Asymmetry 1999, 10, 1223-1242.
P.; Zanda, M. In ref 1a, pp 107-160. Bravo, P.; Bruch e´ , L.; Crucianelli,
M.; Viani, F.; Zanda, M. In ref 1b, pp 98-116. Zanda, M.; Bravo, P.;
Volonterio, A. In ref 1b, pp 127-141. (c) Soloshonok, V. A. In ref 1a,
pp 229-262; in ref 1b, pp 74-83. (d) Yamazaki, T. In ref 1a, pp 263-
2
86. (e) Uneyama, K. In ref 1a, pp 391-418. (f) Ishii, A.; Mikami, K.
In ref 1b, pp 60-71. (g) Gyenes, F.; Kornilov, A.; Welch, J . T. In ref
b, pp 182-192. (h) Kirk, K. L.; Herbert, B.; Lu, S.-F.; J ayachandran,
1
B.; Padgett, W. L.; Olufunke, O.; Daly, J . W.; Haufe, G.; Laue, K. W.
In ref 1b, pp 194-209. (i) Hiyama, T.; Kusumoto, T.; Matsutani, H. In
ref 1b, pp 226-238. (j) Mikami, K. In ref 1b, pp 255-269. (k) Haufe,
G.; Kr o¨ ger, S. Amino Acids 1996, 11, 409-424.
(
3) Ramachandran, P. V.; Brown, H. C. In ref 1a, pp 179-228; in
(10) Tranel, F.; Haufe, G. Tetrahedron: Asymmetry 2000, 11, 889-
896 and references therein.
ref 1b, pp 22-37.
1
0.1021/jo016331r CCC: $22.00 © 2002 American Chemical Society
Published on Web 04/06/2002

3
016 J . Org. Chem., Vol. 67, No. 9, 2002
W o¨ lker and Haufe
reactions, we needed both enantiomers of â-fluorocyclo-
alkanols of ring size C to C . Recently, we synthesized
S,S)-(+)-2-fluorocyclohexanol and (S,S)-(+)-2-fluoro-
6
8
(
cycloheptanol with maximum 72% ee and 65% ee, re-
spectively, by asymmetric ring opening of the corre-
sponding epoxides with silver fluoride mediated by (R,R)-
F igu r e 1. Enantiomer preferably transferred by lipases
according to the Kazlauskas rule.19
(-)-(salen)chromium chloride. However, almost a stoichio-
metric amount of the chiral Lewis acid was necessary,
and the eight-membered compound was not available in
this way.7b Herein, we present the preparation of these
compounds with significantly higher enantiomeric ex-
cesses using deracemization of the corresponding esters
or the acylation of the fluorohydrins in organic solvents.
ing acyl compounds 3 or 4 using the respective carboxylic
acid anhydrides.
Resu lts a n d Discu ssion
Vicinal fluorohydrins can be synthesized from epoxides
N N
by either S 1-like or S 2-type ring opening depending
1
4
on the applied hydrofluorinating agent. While reactions
with HF itself or HF in combination with bases such as
tetrahydrofuran or pyridine are occasionally accompanied
by rearrangements,7 such competing processes were not
,15
observed with less acidic, but more nucleophilic reagents
N‚3HF.1
6,17
We obtained the desired fluoro-
N‚
HF at temperatures between 115 and 155 °C for 3-5
h. The fluorohydrins 2 were converted to the correspond-
such as Et
3
hydrins 2 by treatment of the epoxides 1 with neat Et
3
Having the acetates 3 or the chloroacetates 4 in hand,
we investigated hydrolyses using lipases from Pseudo-
monas cepacia (PCL), Candida antarctica (CAL) or
Candida rugosa (CRL). PCL and CRL have already been
applied for hydrolyses of esters of trans-2-azidocycloal-
3
(
11) (a) Yamazaki, T.; Asai, M.; Ohnogi, T.; Lin, J . T.; Kitazume, T.
J . Fluorine Chem. 1987, 35, 537-553. (b) Yamazaki, T.; Ichikawa, S.;
Kitazume, T. J . Chem. Soc., Chem. Commun. 1989, 253-255. (d)
Bucciarelli, M.; Forni, A.; Moretti, I.; Prati, F.; Torre, G.; Resnati, G.;
Bravo, P. Tetrahedron 1989, 45, 7505-7514. (c) Murata, K.; Kitazume,
T. Tetrahedron: Asymmetry 1993, 4, 889-892. (d) Goj, O.; Burchardt,
A.; Haufe, G. Tetrahedron: Asymmetry 1997, 8, 399-408. (e) Skupin,
R.; Cooper, T. G.; Fr o¨ hlich, R.; Prigge, J .; Haufe, G. Tetrahedron:
Asymmetry 1997, 8, 2453-2464.
1
8
kanols or esters of trans-2-bromocycloalkanols. In all
cases, (R)-selectivity was observed according to Kazlaus-
19
kas’ rule in cases when the large substituent has also
the higher priority according to the CIP nomenclature
(cf. Figure 1). From C. antarctica two isozymes A and B
are produced, which differ in selectivity to a certain
extent.20 In this study, we used Novozym435, which
contains the isozyme B. Using these three lipases, we
hydrolyzed the corresponding racemic esters to about
(12) (a) Gaspar, J .; Guerrero, A. Tetrahedron: Asymmetry 1995, 6,
2
2
31-238. (b) Sattler, A.; Haufe, G. Tetrahedron: Asymmetry 1995, 6,
841-2848. (c) Takeda, M.; Ishizuka, T.; Itoh, K.; Kitazume, T. J .
Fluorine Chem. 1995, 75, 111-113. (d) Hamada, H.; Shiromoto, M.;
Funahashi, M.; Itoh, T.; Nakamura, K. J . Org. Chem. 1996, 61, 2332-
5
0% conversion in a phosphate buffer (pH ) 7.0) at room
2
336. (e) Petschen, I.; Malo, E. A.; Bosch, M. P.; Guerrero, A.
Tetrahedron: Asymmetry 1996, 7, 2135-2143. (f) Takahashi, T.;
Fukushima, A.; Tanaka, Y.; Segawa, M.; Hori, H.; Takeuchi, Y.;
Burchardt, A.; Haufe, G. Chirality 2000, 12, 458-463. (g) Runge, M.;
Haufe, G. J . Org. Chem. 2000, 65, 8737-8742. (h) Burchardt, A.;
Takahashi, T.; Takeuchi, Y.; Haufe, G. J . Org. Chem. 2001, 66, 2078-
temperature. The results are shown in Table 1.
2
084.
(
13) (a) Pietz, S.; Fr o¨ hlich, R.; Haufe, G. Tetrahedron 1997, 53,
1
5
7055-17066. (b) Pietz, S.; W o¨ lker, D.; Haufe, G. Tetrahedron 1997,
3, 17067-17078. (c) Abraham, W.-R.; Arfmann, H.-A.; Kieslich, K.;
Haufe, G. Biocatal. Biotransform. 2000, 18, 283-290.
(14) Reviews: (a) B o¨ hm, S. Fluorination with Ring Opening of
Epoxides. In Houben-Weyl, Methods of Organic Chemistry, 4th ed.;
Baasner, B., Hagemann, H., Tatlow, J . C., Eds.; Thieme-Verlag:
Stuttgart, 1999; Vol. E10b , pp 137-158 (refs until 1990). (b) Mieth-
1
Hydrolysis of the acetates 3 took a very long time to
reach 50% conversion for all enzymes. The enantioselec-
tivity of PCL was very high for the six- and the seven-
chen, R.; Peters, D. Introduction of Fluoride with Anhydrous Hydrogen
Fluoride, Aqueous Solutions of Hydrogen Fluoride, and HF-Base
Complexes. In Houben-Weyl, Methods of Organic Chemistry, 4th ed.;
Baasner, B., Hagemann, H., Tatlow, J . C., Eds.; Thieme-Verlag:
Stuttgart, 1999; Vol. E10a, pp 95-158. (c) Yoneda, N. Tetrahedron
21
membered ring esters (E > 65), yielding the (R,R)-
fluorohydrins with about 90% ee and the remaining (S,S)-
acetates with >92% ee. The selectivity for the eight-
membered ring esters was low (Table 1, entries 1-3). For
1
991, 47, 5329-5365. (d) Olah, G. A.; Li, X. Y. In Synthetic Fluorine
Chemistry; Olah, G. A., Chambers, R. D., Prakash, G. K. S., Eds.; Wiley
Sons: New York, 1992; pp 163-204.
15) (a) Olah, G. A.; Meidar, D. Isr. J . Chem. 1978, 17, 148-149.
b) Olah, G. A.; Welch, J . T.; Vankar, Y.; Nojima, M.; Kerekes, I.; Olah,
&
(
(18) (a) Xie, Z.-F.; Nakamura, I.; Suemune, H.; Sakai, K. J . Chem.
Soc., Chem. Commun. 1988, 966-967. (b) H o¨ nig, H.; Seufer-Wasser-
thal, P.; F u¨ l o¨ p, F. J . Chem. Soc., Perkin Trans. 1 1989, 2341-2344.
(c) Gupta, A. K.; Kazlauskas, R. J . Tetrahedron: Asymmetry 1993, 4,
879-888.
(19) Kazlauskas, R. J .; Weissfloch, A. N. E.; Rappoport, A. T.; Cuccia,
L. A. J . Org. Chem. 1991, 56, 2656-2665.
(20) (a) Patkar, S. A.; Bj o¨ rkling, F.; Zyndel, M.; Schulein, M.;
Svendsen, A.; Heldt-Hansen, H. P.; Gormsen, E. Ind. J . Chem. 1993,
32B, 76-80; Anderson, E. M.; Larsson, K. M.; Kirk, O. Biocatalysis
Biotrans. 1998, 16, 181-204.
(21) Chen, C.-S.; Fujimoto, Y.; Girdaukas, G.; Sih, C. S. J . Am. Chem.
Soc. 1982, 104, 2794-2799.
(
J . A. J . Org. Chem. 1979, 44, 3872-3881. (c) Alvernhe, G.; Laurent,
A.; Haufe, G. J . Fluorine Chem. 1986, 34, 147-156. (d) Umezawa, J .;
Takahashi, O.; Furuhashi, K.; Nohira, H. Tetrahedron: Asymmetry
1
9
993, 4, 2053-2060. (e) Skupin, R.; Haufe, G. J . Fluorine Chem. 1998,
2, 157-165.
(
16) Reviews: (a) McClinton, M. A. Aldrichim. Acta 1995, 28, 31-
3
5. (b) Haufe, G. J . Prakt. Chem./ Chem. Ztg. 1996, 338, 99-113 and
references therein.
17) (a) Aranda, G.; J ullien, J .; Martin, J . A. Bull. Soc. Chim. Fr.
(
1
1
966, 2850-2851. (b) Goj, O.; Haufe, G. Liebigs Ann. 1996, 1289-
294.

Optically Active Vicinal Fluorohydrins
J . Org. Chem., Vol. 67, No. 9, 2002 3017
Ta ble 1. Lip a se-Ca ta lyzed Hyd r olysis of Aceta tes (()-3 or Ch lor oa ceta tes (()-4
conversion
(%)
entry
1
acetate
lipase
PCL
time
4 d
products
yield (%)
ee (%)
E21
(()-3a
53
50
48
54
50
63
45
49
42
53
47
55
50
50
57
42
41
41
(S,S)-(+)-3a
R,R)-(-)-2a
35
29
35
43
44
43
35
47
40
37
23
44
41
40
42
41
46
39
35
29
41
42
30
47
43
40
39
37
23
44
50
34
49
33
46
42
>95
87
92
91
26
44
66
48
6
65
66
79
67
2
4
7
5
1
(
2
3
4
5
6
7
8
9
(()-3b
(()-3c
(()-3a
(()-3b
(()-3c
(()-3a
(()-3b
(()-3c
(()-4a
(()-4b
(()-4c
(()-4a
(()-4b
(()-4c
(()-4a
(()-4b
(()-4c
PCL
PCL
CAL
CAL
CAL
CRL
CRL
CRL
PCL
PCL
PCL
CAL
CAL
CAL
CRL
CRL
CRL
7 d
25 d
5 h
(S,S)-(+)-3b
R,R)-(-)-2b
(S,S)-(+)-3c
R,R)-(-)-2c
(S,S)-(+)-3a
R,R)-(-)-2a
(R,R)-(-)-3b
S,S)-(+)-2b
(R,R)-(-)-3c
S,S)-(+)-2c
(S,S)-(+)-3a
R,R)-(-)-2a
(S,S)-(+)-3b
R,R)-(-)-2b
(S,S)-(+)-3c
R,R)-(-)-2c
(S,S)-(+)-4a
R,R)-(-)-2a
(S,S)-(+)-4b
R,R)-(-)-2b
(S,S)-(+)-4c
R,R)-(-)-2c
(S,S)-(+)-4a
R,R)-(-)-2a
(R,R)-(-)-4b
S,S)-(+)-2b
(R,R)-(-)-4c
S,S)-(+)-2c
(S,S)-(+)-4a
R,R)-(-)-2a
(S,S)-(+)-4b
R,R)-(-)-2b
(S,S)-(+)-4c
R,R)-(-)-2c
(
(
(
5 h
(
5
1
4
5
17 h
20 h
10 h
23 h
2.75 h
4.5 h
16 d
1.2 h
5 h
66
42
80
82
78
75
71
86
> 95
75
75
73
51
28
< 3
< 3
21
21
47
38
28
34
34
54
50
43
(
220
20
23
15
217
25
55
18
27
12
4
2
1
1
2
2
3
4
3
(
(
(
1
1
1
1
1
1
1
1
1
0
1
2
3
4
5
6
7
8
(
(
(
(
(
5 h
(
15 min
(
3
6
5
10
3
10 min
90 min
(
(
CAL, the reaction time was shorter. However, the enan-
tioselectivity of this enzyme was poor, particularly for
the seven-membered ring (Table 1, entry 5). We find it
interesting that the enantiopreference of CAL was re-
versed for the seven- and eight-membered ring com-
pounds as compared with the cyclohexane derivatives
ses of the esters in a buffer system using the same
enzyme.22
It is advantageous to use enol esters as acylating
agents in general to ensure on one hand the irrevers-
ibility of the reaction, and therefore the most probable
enantioselectivity, and on the other hand the enhance-
ment of the reaction rate by using a great excess of the
reagent. Thus, the fluorohydrins 2 were acylated with
the above-mentioned lipases in combination with vinyl
acetate or vinyl chloroacetate.
(Table 1, entries 4-6 and 13-15) and compared to the
reactions of the other lipases. For the hydrolysis of
acetates 3 using CRL, the enantiomeric excess was
reasonable for all products (Table 1, entries 7-9), while
the selectivity was lower in case of the chloro acetates 4
(Table 1, entries 16-18).
As expected, hydrolysis of the corresponding chloro-
acetates 4 with all lipases proceeded much faster than
those of the acetates. However, the enantioselectivity in
most cases was much lower when compared to hydrolysis
of the corresponding acetates.
Lipase-catalyzed transformations in organic solvents
have recently become more common. The better solubility
of most substrates in organic solvents compared to
aqueous buffer systems and the easier separation of the
mostly immobilized lipases favor reactions in organic
media. A more facile monitoring of the reaction’s progress
is possible, and the isolation of the products is simpler
for reactions in organic media. The polarity of organic
solvents is generally less than that of aqueous buffers.
Thus, the polar interactions of different parts of the
protein become stronger and the enzyme becomes con-
formationally more rigid. Therefore, lipase-catalyzed
esterifications in organic solvents or in the acylating
reagent itself sometimes proceed with higher enantio-
selectivity as compared with the corresponding hydroly-
The results of acetylation of 2 with vinyl acetate by
using PCL immobilized on Celite in different solvents are
shown in Table 2.
With trans-2-fluorocyclohexanol 2a there was not a big
difference in enantioselectivity in different solvents.
However, in diisopropyl ether (DIPE) or vinyl acetate
itself, the highest ee was found, while the reactions in
cyclohexane proceeded faster. In the case of trans-2-
fluorocycloheptanol 2b, the reaction in all solvents took
much more time and the enantioselectivity was slightly
lower. The best results were obtained in DIPE for 2a or
(
22) E.g. (a) Wu, S. H.; Guo, Z. W.; Sih, C. J . J . Am. Chem. Soc.
990, 112, 1990-1995. (b) Fitzpatrick, P. A.; Klibanov, A. M. J . Am.
Chem. Soc. 1991, 113, 3166-3171.
1

3
018 J . Org. Chem., Vol. 67, No. 9, 2002
W o¨ lker and Haufe
Ta ble 2. En a n tioselectivity of Acetyla tion s of F lu or oh yd r in s 2 w ith Vin yl Aceta te Ca ta lyzed by P CL Im m obilized on
Celite Dep en d en t on Solven ts
entry
1
fluorohydrin
solvent
DIPE
time
25 h
conversion (%)
50
products
yield (%)
ee (%)
E21
(()-2a
(R,R)-(-)-3a
S,S)-(+)-2a
40
48
39
39
41
33
29
35
40
31
30
30
32
29
37
48
31
39
35
27
38
36
20
37
18
37
95
86
82
83
86
>95
94
84
75
85
87
74
84
68
84
76
86
70
90
75
24
23
23
11
23
8
146
37
24
35
55
48
115
30
16
33
41
15
27
13
28
19
32
15
53
18
2
(
2
3
4
5
6
7
8
9
(()-2a
(()-2a
(()-2a
(()-2a
(()-2b
(()-2b
(()-2b
(()-2b
(()-2b
(()-2c
(()-2c
(()-2c
toluene
46 h
17 h
49 h
99 h
3 d
49
53
50
50
50
48
49
48
49
49
32
31
(R,R)-(-)-3a
S,S)-(+)-2a
(R,R)-(-)-3a
S,S)-(+)-2a
(R,R)-(-)-3a
S,S)-(+)-2a
(R,R)-(-)-3a
S,S)-(+)-2a
(R,R)-(-)-3b
S,S)-(+)-2b
(R,R)-(-)-3b
S,S)-(+)-2b
(R,R)-(-)-3b
S,S)-(+)-2b
(R,R)-(-)-3b
S,S)-(+)-2b
(R,R)-(-)-3b
S,S)-(+)-2b
(R,R)-(-)-3c
S,S)-(+)-2c
(R,R)-(-)-3c
S,S)-(+)-2c
(R,R)-(-)-3c
S,S)-(+)-2c
(
cyclohexane
vinyl acetate
THF
(
(
(
DIPE
(
toluene
15 d
2 d
(
cyclohexane
vinyl acetate
THF
(
15 d
16 d
19 d
42 d
56 d
(
1
1
1
1
0
1
2
3
(
DIPE
(
2
2
2
2
cyclohexane
vinyl acetate
(
(
2
THF for 2b, respectively (Table 2, entries 1 and 10). In
contrast with the eight-membered ring fluorohydrin 2c,
only the acetylation in DIPE came to 49% conversion
after 19 days, but the enantioselectivity was very poor.
Only 32 or 31% conversion was found in cyclohexane or
vinyl acetate after 42 or 56 days, respectively, and the
enantioselectivity was also very poor (Table 2, entries 12
and 13).
The reaction time with all fluorohydrins was much
shorter with vinyl chloroacetate and PCL in DIPE when
compared to the corresponding reactions with vinyl
acetate. The enantioselectivity was good with the six-
membered and quite good with the seven-membered ring
fluorohydrins. Again, the cyclooctane derivative showed
an unacceptable selectivity (Table 3, entries 1-3).
Next we examined the esterifications of the fluoro-
hydrins 2 with vinyl acetate in DIPE. Only the six-
membered compound 2a showed reasonable enantiose-
lectivity (Table 3, entries 4-6). Interestingly, reverse
stereoselection was found for the eight-membered ring
fluorohydrin. With vinyl chloroacetate as the acylation
reagent the reactions became very fast in DIPE. After
The acetylation in pure vinyl acetate of all fluorohy-
drins 2 was very slow. Vinyl chloroacetate, when used
as the acylation reagent, produced faster reactions. In
contrast to the esterifications with PCL or CAL, the
enantioselectivity was almost independent of the ring size
and the acylation reagent.
Deter m in a tion of th e Absolu te Con figu r a tion .
According to the Kazlauskas rule19 for the enantiopref-
erence of P. cepacia lipase (PCL) and several other lipases
of this type such as CRL, the enantiomer of 3 shown in
Figure 1 should be transferred preferably. Thus, because
the CHF group is larger than a CH group, the (R,R)-
2
enantiomers of acetates 3 should be hydrolyzed faster
than the (S,S)-enantiomers.
To prove whether polar interactions such as hydrogen
bonding of the protein to the F atom of the C-F-bond,
which seems to be responsible for the modification of the
biological activity of fluorinated compounds as compared
to their nonfluorinated parent compounds,24 do contradict
the geometry-based rule, we determined the absolute
configuration of some representative products by CD
spectroscopy.25 CD spectra of approximately 5 × 10
-3
M
4
-5 min, more than 50% of the fluorohydrins were
solutions were measured in acetonitrile of the acetates
converted to product. In contrast to all other esterifica-
tions, there was no enantioselectivity obtained for the
esterification of 2a , and also for the seven-membered 2b
the selectivity was quite low. Surprisingly, for the eight-
membered 2c a quite high enantiomeric excess was found
for the remaining fluorohydrin (R,R)-(-)-2c after 55%
conversion (Table 3, entry 11). The reactions became
much slower in cyclohexane, while the enantioselectivity
did not increase significantly for the six- and the seven-
membered ring systems and, in fact, decreased for the
cyclooctane derivative. For all chloroacetylations with
CAL, the enantiopreference was the reverse of that
obtained in the reactions catalyzed by PCL or CRL (Table
(23) Miyazawa, T.; Kurita, S.; Ueji, S.; Yamada, T.; Kuwata, S. J .
Chem. Soc., Perkin Trans. 1 1992, 2253-2255.
(24) (a) Takahashi, L. H.; Radhakrishnan, R.; Rosenfield, R. E., J r.;
Meyer, F. E., J r.; Trainor, D. A. J . Am. Chem. Soc. 1989, 111, 3368-
3374. (b) Abeles, R. H.; Alston, T. A. J . Biol. Chem. 1990, 265, 16705-
1
6708. (c) Kov a´ cs, T.; Pabuccuoglu, A.; Lesiak, K.; Torrence, P. F.
Bioorg. Chem. 1993, 21, 192-208. (d) Mattos, C.; Rasmussen, B.; Ding,
X.; Petsko, G. A.; Ringe, D. Nat. Struct. Biol. 1994, 1, 55-58. (e)
Chapeau, M.-C.; Frey, P. A. J . Org. Chem. 1994, 59, 6994-6998. (f)
O’Hagan, D.; Rzepa, H. S. J . Chem. Soc., Chem. Commun. 1997, 645-
6
52. (g) Yamazaki, T.; Kitazume, T. Coordination Ability of Fluorine
to Proton or Metals Based on Experimental and Theoretical Evidence.
In Enantiocontrolled Synthesis of Fluoro-Organic Compounds; Solo-
shonok, V. A., Ed.; J ohn Wiley & Sons: Chichester, 1999; pp 575-
6
00. (h) Desiraju, G. R.; Steiner, T. The Weak Hydrogen Bond in
Structural Chemistry and Biology; IUCr Monographs on Crystal-
lography, Vol. 9; Oxford University Press: Oxford, 1999.
3
). A similar observation was made for the transesteri-
(25) Legrand, M.; Pougier, M. J . In StereochemistrysFundamentals
fication of methyl mandelate using vinyl acetate and a
and Methods; Kagan, H. B., Ed.; Thieme-Verlag: Stuttgart, 1977; Vol.
2, Dipole Moments, CD or ORD, pp 31-183.
lipase of Pseudomonas sp.23

Optically Active Vicinal Fluorohydrins
J . Org. Chem., Vol. 67, No. 9, 2002 3019
Ta ble 3. Acyla tion s of F lu or oh yd r in s 2 w ith Lip a ses Im m obilized on Celite 577 (P CL a n d CAL) or on La ctose (CRL)
entry fluorohydrin
solvent
DIPE
lipase
PCL
acylation reagent
vinyl chloroacetate
time
conversion (%)
45
products
yield (%) ee (%) E21
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
(()-2a
(()-2b
(()-2c
(()-2a
(()-2b
(()-2c
(()-2a
(()-2a
(()-2b
(()-2b
(()-2c
(()-2c
(()-2a
(()-2b
(()-2c
(()-2a
(()-2b
(()-2c
90 min
(R,R)-(-)-4a
S,S)-(+)-2a
43
39
44
38
39
41
44
41
42
40
40
42
47
35
52
43
51
42
35
48
37
42
51
41
37
39
41
48
20
61
42
40
45
41
47
36
91
81
67
75
18
21
73
65
46
40
30
29
<1
<1
6
47
500
9
52
2
2
14
9
4
4
2
4
1
1
1
1
3
3
3
4
(
DIPE
PCL
PCL
CAL
CAL
CAL
CAL
CAL
CAL
CAL
CAL
CAL
CRL
CRL
CRL
CRL
CRL
CRL
vinyl chloroacetate 135 min
vinyl chloroacetate 330 min
45
52
50
47
50
54
52
55
46
55
56
43
42
21
50
49
41
(R,R)-(-)-4b
S,S)-(+)-2b
(R,R)-(-)-4c
S,S)-(+)-2c
(R,R)-(-)-3a
S,S)-(+)-2a
(R,R)-(-)-3b
S,S)-(+)-2b
(S,S)-(+)-3c
R,R)-(-)-2c
4a
(
DIPE
(
DIPE
vinyl acetate
2 h
3 h
(
DIPE
vinyl acetate
(
DIPE
vinyl acetate
12 h
(
DIPE
vinyl chloroacetate
vinyl chloroacetate
vinyl chloroacetate
4 min
2
a
cyclohexane
DIPE
70 min
5 min
(S,S)-(+)-4a
R,R)-(-)-2a
(S,S)-(+)-4b
R,R)-(-)-2b
(S,S)-(+)-4b
R,R)-(-)-2b
(S,S)-(+)-4c
R,R)-(-)-2c
(S,S)-(+)-4c
R,R)-(-)-2c
(R,R)-(-)-3a
S,S)-(+)-2a
(R,R)-(-)-3b
S,S)-(+)-2b
(R,R)-(-)-3c
S,S)-(+)-2c
(R,R)-(-)-4a
S,S)-(+)-2a
(R,R)-(-)-4b
S,S)-(+)-2b
(R,R)-(-)-4c
S,S)-(+)-2c
(
6
31
38
35
38
67
87
33
41
78
56
83
53
87
24
80
60
82
68
86
52
(
1
1
1
1
1
1
1
1
1
cyclohexane
DIPE
vinyl chloroacetate 180 min
(
vinyl chloroacetate
vinyl chloroacetate
vinyl acetate
5 min
14 h
13
16
3
(
cyclohexane
(
3
35 d
36 d
15 d
22 d
2 d
15
12
20
11
18
25
22
7
24
12
24
12
(
vinyl acetate
(
vinyl acetate
(
vinyl chloroacetate
vinyl chloroacetate
vinyl chloroacetate
(
(
19 d
(
(
2
-)-3a (Table 2, entry 1, 95% ee), (-)-3b (Table 1, entry
, after acetylation of (-)-2b with Ac O/pyridine, 90% ee),
2
and (+)-3c (Table 3, entry 11, after hydrolysis of the
chloroacetate (+)-4c and acetylation of the formed (+)-
2
c with Ac
at 214 nm for all acetates. The CD was positive for (-)-
a and (-)-3b and was negative for (+)-3c over the
2
O/pyridine, 75% ee). The λmax was determined
3
complete range of wavelengths. From the carboxylate
sector rules23 relevant for the acetate chromophores, an
(R)-configuration for the acetoxy-substituted stereogenic
center is predicted for (-)-3a and (-)-3b, while the (S)-
configuration follows for (+)-3c on the basis of the
following assumptions: the ring methylene groups are
arranged preferably in a chair configuration (zigzag
orientation), the OAc group is smaller than the CHFR
moiety, and the H attached to C-1 and the carbonyl group
both point in the same direction. Thus, the absolute
configuration determined by CD spectroscopy for (-)-3a
and (-)-3b obtained in the corresponding transforma-
tions with PCL is consistent with that predicted by the
F igu r e 2. CD spectra of (a) (1R,2R)-(-)-1-acetoxy-2-fluoro-
-3
cycloheptane (3b), 90% ee, 6.75 × 10 M (corrected to 100%
ee) and (b) (1S,2S)-(+)-1-acetoxy-2-fluorocyclooctane (3c), 75%
-
3
ee, 5.6 × 10 M (corrected to 100% ee), each in CH
3
CN at 20
°C.
acetates 3 or chloroacetates 4 may be used. Among the
three tested lipases PCL, CAL, and CRL, the first showed
very good enantioselectivity for the six- and the seven-
membered ring compounds 3a and 3b, while low selectiv-
ity was observed in the eight-membered ring compound
1
9
Kazlauskas rule. In contrast, the transformation of the
eight-membered ring compounds with CAL are in dis-
agreement with the above-mentioned rule. An indepen-
dent proof that the absolute configuration of (+)-2a was
3
c. Comparing the reactions with PCL of the acetates 3
with the chloroacetates 4 the latter were hydrolyzed
faster, as expected, but the reactions gave slightly lower
ee values. CRL can be recommended for all ring sizes.
The enantioselectivity of the hydrolysis of the acetates
(1S,2S) was found by the X-ray structural analysis of two
products produced by microbial hydroxylation of the
N-phenylcarbamate of (+)-2a .26
3
a and 3c is very high and slightly less so for the seven-
Con clu sion
membered acetate 3b . The hydrolysis of the chloro-
acetates occurred much faster, but the ee values were
small. When CAL was used as the biocatalyst, the
enantioselectivity of the reaction was poor for all ring
sizes, both for acetates and chloroacetates. The reverse
For deracemizations of vicinal cyclic fluorohydrins of
ring sizes C to C , hydrolyses of the corresponding
6 8
(
26) Haufe, G.; W o¨ lker, D.; Fr o¨ hlich, R. J . Org. Chem. 2002, 67,
3
022-3028.

3
020 J . Org. Chem., Vol. 67, No. 9, 2002
W o¨ lker and Haufe
diastereoselection was obtained for the seven- and the
eight-membered acetates and chloroacetates.
tr a n s-2-F lu or ocycloh ep ta n ol 2b: yield 1.87 g (71%); bp
5 °C/0.01 bar (lit.1 bp 90-92 °C/25 mm). The spectroscopic
3a
7
data agree with those reported in ref 13a.
PCL and CRL may also be used for deracemization of
fluorohydrins by acetylation or chloroacetylation in sev-
eral organic solvents. Diisopropyl ether (DIPE), cyclo-
hexane, or the acetylating reagent itself were shown to
be the most suitable solvents in the case of the reactions
with PCL as the immobilized biocatalyst. The highest
enantioselectivity was found for the six- and the seven-
membered fluorohydrins 2a and 2b, while this lipase did
not give acceptable results for the eight-membered fluo-
rohydrin 2c. The acylations with PCL of 2c were very
slow both in pure vinyl acetate or vinyl chloroacetate.
For CAL, the acetylations proceeded relatively fast, but
the enantioselectivity was poor for all ring sizes and with
both acylation reagents. Furthermore, for acetylation, the
enantiopreference obtained for the six- and seven-
membered ring fluorohydrin changed for the eight-
membered fluorohydrin. In chloroacetylation, reverse
selectivity by CAL compared to that of PCL and CRL was
observed for all ring sizes.
tr a n s-2-F lu or ocycloocta n ol 2c: yield 1.58 g (54%, after
chromatographic separation) (lit.27 bp 60-65 °C/2 mm);
1
H
NMR δ 1.32-2.09 (m), 2.25 (br s, 1H), 3.78-3.89 (m, 1H), 4.46
2
3
3
(
ddt, J H,F ) 48.6 Hz, J Ha,Ha ) 8.6 Hz, J Ha,He ) 2.7 Hz, 1H);
1
3
2
C NMR δ 23.3 (t), 23.5 (t, J
C,F
) 7.6 Hz), 26.1 (t), 29.8 (dt,
C,F ) 10.2 Hz), 74.2 (dd,
2J C,F ) 5.1 Hz), 30.1 (dt,
3
J
2
J
)
C,F
1
19
20.3 Hz), 99.2 (dd, J C,F ) 162.8 Hz); F NMR δ -182.1 (m);
GC-MS m/z 146 (3), 129 (3), 128 (18), 103 (6), 100 (18), 95
(
(
6), 83 (8), 82 (17), 81 (20), 73 (4), 72 (13), 69 (9), 67 (28), 58
9), 57 (100).
Acetyla tion of F lu or oh yd r in s 2. A solution of the fluo-
rohydrin 2 (5 mmol), acetic anhydride (0.51 g, 5 mmol), and
pyridine (0.45 g, 6 mmol) was heated at 110 °C for 3 h. After
being cooled to room temperature, the mixture was dissolved
in diethyl ether (15 mL) and washed with diluted HCl (3 × 5
mL) and water (5 mL). The organic layer was dried over
magnesium sulfate, the solvent was evaporated, and the
residue was purified by column chromatography (silica gel,
pentane/diethyl ether 1:1) to give colorless liquids of the
acetates 3.
tr a n s-1-Acetoxy-2-flu or ocycloh exa n e 3a : yield 0.73 g
2
8
(
91%). Spectroscopic data agree with published data.
tr a n s-1-Acetoxy-2-flu or ocycloh ep ta n e 3b: yield 0.81 g
Exp er im en ta l Section
1
(
93%); H NMR δ 1.38-1.94 (m, 10H), 2.01 (s, 3H), 4.54 (dm,
Gen er a l Meth od s. H NMR (300.1 MHz), 13C NMR (75.5
1
2
13
J
H,F
) 48.3 Hz), 4.90-5.02 (m, 1H); C NMR δ 20.8 (q), 21.3
3
1
9
3
MHz), and F NMR spectra (282.3 MHz) were recorded from
ca. 20% solutions in CDCl . Chemical shifts are reported as δ
values (ppm) relative to TMS ( H), CDCl
respectively, as internal standards. The multiplicity of
signals was determined by the DEPT operation. Mass spectra
electron impact ionization, 70 eV) were recorded by GC/MS
(dt, J
) 7.6 Hz), 22.7 (t), 27.9 (t), 29.1 (dt, J
) 7.6 Hz),
C,F
C,F
2
2
3
30.5 (dt,
J
C,F
) 20.4 Hz), 76.5 (dd,
J
C,F
) 33.1 Hz), 95.5 (dd,
1
13
19
1
19
3
( C) or CFCl
3
( F),
J C,F ) 173.0 Hz), 169.8 (s); F NMR δ -170.8 (m); GC-MS
m/z 174 (0.2), 159 (0.1), 156 (0.4), 132 (21), 114 (30), 112 (27),
99 (10), 94 (20), 85 (8), 79 (7), 72 (9), 68 (14), 67 (8), 55 (11), 54
(4), 44 (8), 43 (100). Anal. Calcd for C H FO (174.2): C, 62.06;
1
3
C
(
9
15
2
coupling. The conversion of substrates during enzymatic
transformations was followed by GC (quartz capillary columns,
5 m × 0.33 mm, 0.52 µm HP-1 and 30 m × 0.32 mm, 0.25 µm
SPB-1, temperature program, 40 f 280 °C with 10 °C/min
heating rate, N as the carrier gas). The ratio of compounds
was determined by integration of the peak area and corrected
by a factor that was determined from the ratio of peak areas
of a precisely weighted mixture of the respective fluorohydrin
and the corresponding acetate or chloroacetate. The products
of enzymatic transformations were separated by column
chromatography (silica gel, 70-230 mesh, diethyl ether/
pentane 1:1). The enantiomeric excesses of the fluorohydrins
and the corresponding acetates and chloroacetates were
determined by chiral GC using a â-cyclodextrin column, 30m
H, 8.68. Found: C, 61.64; H, 8.96.
tr a n s-1-Acetoxy-2-flu or ocycloocta n e 3c: Yield 0.84 g
2
1
(
89%); H NMR δ 1.33-2.00 (m, 12H), 2.04 (s, 3H), 4.53 (dm,
2
13
J
H,F ) 48.4 Hz), 4.90-5.02 (m, 1H); C NMR δ 21.2 (q), 23.5
3 3
2
(
7
9
dt, J C,F ) 5.1 Hz), 24.0 (t), 25.4 (t), 25.8 (t,), 28.5 (dt, J C,F
)
2
2
.6 Hz), 29.5 (dt, J C,F ) 20.3 Hz), 76.2 (dd, J C,F ) 22.9 Hz),
1 19
5.0 (dd, J C,F ) 172.9 Hz), 170.3 (s); F NMR δ -173.1 (m);
GC-MS m/z 189 (0.2), 188 (2), 171 (0.6), 170 (5), 160 (3), 146
(
(
5
32), 128 (72), 126 (52), 108 (23), 100 (90), 98 (74), 86 (20), 85
25), 82 (57), 76 (38), 72 (36), 67 (49), 59 (22), 57 (30), 55 (48),
4 (20), 44 (34), 43 (100), 41 (66), 39 (28). Anal. Calcd for
(188.2): C, 63.81; H, 9.10. Found: C, 63.57; H, 9.38.
Ch lor oa cetyla tion of F lu or oh yd r in s 2. A solution of the
10 2
C H17FO
fluorohydrin 2 (1 mmol) and chloroacetic anhydride (0.17 g, 1
mmol) was heated to 80 °C for 8 h. After being cooled to room
temperature, the mixture was dissolved in diethyl ether (5 mL)
and poured into water (8 mL). The organic layer was sepa-
rated, and the aqueous phase was extracted with diethyl ether
×
0.25 mm, 0.25 µm, Beta-Dex 120, isotherm 96 °C for 2a and
11 °C for 2b , N as carrier gas. trans-2-Fluorocyclooctanol
c was silylated (0.5 mg of 2c and two drops of N,O-bis-
1
2
2
(
trimethylsilyl)acetamide were heated to 85 °C for 2 h) prior
to GC analyses (isotherm, 110 °C). The E value given in the
(
2 × 5 mL). The combined ethereal phase was washed with
2
1
tables is a measure for the selectivity of an enzyme. CD
water (5 mL) and dried over magnesium sulfate. After evapo-
ration of the solvent, the residue was purified by column
chromatography (silica gel, pentane/diethyl ether 1:1).
-
3
spectra were determined of about 5 × 10 M solutions in
acetonitrile. Optical rotations were determined at Na line, λ
589 nm. Elemantal analyses were carried out by the
Mikroanalytisches Laboratorium, Organische Chemie”, Uni-
D
)
“
tr a n s-1-Ch lor oa cetoxy-2-flu or ocycloh exa n e 4a : yield
1
0
.17 g (85%); mp 34-37 °C; H NMR δ 1.18-1.81 (m, 6H),
versity of M u¨ nster.
2
1
.96-2.17 (m, 2H), 4.05 (s, 2H), 4.41 (dddd, J H,F ) 50.6 Hz,
Syn th esis of 2-F lu or ocycloa lk a n ols 2, 1-Acetoxy-2-
flu or ocycloa lk a n es 3, a n d 1-Ch lor oa cetoxy-2-flu or oa l-
k a n es 4. Rin g Op en in g of Ep oxid es 1 w ith Tr ieth yla m in e
Tr ish yd r ogen F lu or id e. In a glass vessel, the corresponding
3
3
3
J
Ha,Ha ) 8.4 Hz, J Ha,Ha ) 10.4 Hz, J Ha,He ) 4.9 Hz, 1H), 4.85-
13 3
4
2
7
(
(
.96 (m, 1H); C NMR δ 22.7 (dt, J C,F ) 10.2 Hz), 23.0 (t),
9.2 (dt, 3
C,F ) 7.6 Hz), 30.4 (dt, 2
J C,F ) 17.8 Hz), 40.9 (t)
1
J
2
5.0 (dd, J C,F ) 20.3 Hz), 91.7 (dd, J C,F ) 178.0 Hz), 166.6
epoxide 1 (20 mmol) and Et
stirred for 3.5 h at 115 °C (2a ), 4 h at 155 °C (2b), or 5 h at
55 °C (2c). After being cooled at room temperature, the
3
N‚3HF (2.38 g, 20 mmol) were
19
2
s); F NMR δ -181.7 (d, J F,H ) 49.6 Hz); GC-MS m/z 176
0.2)/174 (0.5), 145 (2), 119 (4), 118 (28), 101 (23), 100 (100),
1
9
8 (32), 85 (35), 81 (94), 80 (59), 72 (42), 59 (24), 57 (29), 55
mixture was poured into ice-water (25 mL), neutralized with
concentrated ammonia solution, and extracted with methylene
chloride (2 × 20 mL). The combined organic layer was washed
with saturated sodium chloride solution (20 mL) and dried over
magnesium sulfate. The solvent was removed, and the residue
was distilled in vacuo to yield colorless liquids.
(
4
28), 49 (22), 41 (45). Anal. Calcd for C 12FClO (194.6): C,
9.37; H, 6.21. Found: C, 49.67; H, 6.28.
8
H
tr a n s-1-Ch lor oa cetoxy-2-flu or ocycloh ep ta n e 4b: yield
1
0
.17 g (81%); H NMR δ 1.40-2.02 (m, 10H), 4.04 (s, 2H), 4.41
(
27) Pietz, S. Diploma Thesis, University of Leipzig, 1992.
tr a n s-2-F lu or ocycloh exa n ol 2a : yield 1.63 g (69%); mp
(28) Visser, G. W. M.; Bakker, C. N. M.; van Halteren, B. W.;
7
2
3-24 °C (lit. mp 22 °C). The spectroscopic data agree with
Herscheid, J . D. M.; Brinkman, G. A.; Hoekstra, A. Recl. Trav. Chim.
Pays-Bas 1986, 105, 214-219.
those given in ref 6.

Optically Active Vicinal Fluorohydrins
J . Org. Chem., Vol. 67, No. 9, 2002 3021
(
dm, 2J H,F ) 48.8 Hz), 5.00-5.10 (m, 1H); 13C NMR δ 21.6 (dt,
content of the light brownish powder is about 1% according to
ref 29. The immobilized lipases have been stored at 4 °C in a
closed bottle for months without significant loss of activity.
Lip a se-Ca ta lyzed Ester ifica tion s of F lu or oh yd r in s 2.
The corresponding fluorohydrin 2 (1 mmol) and vinyl acetate
or vinyl chloroacetate (2 mmol) were dissolved in the corre-
sponding organic solvent (5 mL) or the acyl donor itself (2 mL),
the immobilized lipase (74 mg PCL, 100 mg CRL, 146 mg CAL,
Novozym435) was added, and the mixture was stirred at room
temperature. The conversion was followed by gas chromatog-
raphy (ca. 0.2 mL aliquots of the mixture were taken and
filtered through silica gel prior to GC). After ca. 50% conversion
of the fluorohydrin 2, the immobilized lipase was filtered off,
the solvent was evaporated, and the remaining mixture of the
fluorohydrins 2 and the acetates 3 or chloroacetates 4 was
separated by column chromatography. The enantiomeric ex-
cess was determined by chiral GC (the results are given in
Tables 2 and 3), and the optical rotation was determined (Table
4, Supporting Information).
3
3
J
C,F ) 7.6 Hz), 22.9 (t), 28.1 (t), 29.3 (dt,
J
C,F ) 10.2 Hz),
2
2
3
9
0.7 (dt, J C,F ) 22.9 Hz), 40.9 (t) 79.6 (dd, J C,F ) 22.9 Hz),
1
1
9
5.3 (dd, J C,F ) 172.9 Hz), 166.5 (s); F NMR δ -171.7 (m);
GC-MS m/z 190 (0.5)/188 (0.9), 160 (0.5), 159 (3), 132 (46),
1
7
15 (10), 114 (100), 112 (35), 99 (36), 95 (96), 86 (38), 79 (30),
7 (84), 72 (28), 68 (54), 67 (47), 59 (18), 57 (32), 55 (53), 49
24), 43 (19), 41 (39), 39 (13).
(
tr a n s-1-Ch lor oa cetoxy-2-flu or ocycloocta n e 4c: yield
1
0
(
(
7
2
-
1
(
.19 g (87%); H NMR δ 1.23-2.06 (m, 12H), 4.04 (s, 2H), 4.41
2
13
dm, J H,F ) 48.3 Hz, 1H), 5.11-5.22 (m, 1H); C NMR δ 23.4
3
3
dt, J C,F ) 7.6 Hz), 23.9 (t), 25.3 (t), 25.5 (t), 28.3 (dt, J C,F
)
)
2
2
.6 Hz), 29.5 (dt, J C,F ) 20.4 Hz), 41.0 (t), 78.4 (dd, J C,F
19
0.3 Hz), 94.6 (dd, 1
J
C,F ) 170.4 Hz), 166.6 (q); F NMR δ
173.2 (m); GC-MS m/z 222 (0.1), 207 (0.6), 174 (8), 161 (6),
46 (40), 145 (7), 129 (12), 128 (100), 109 (67), 100 (96), 95
27), 85 (23), 82 (46), 81 (51), 77 (88), 72 (32), 67 (66).
Lip a se-Ca ta lyzed Hyd r olysis of Aceta tes 3 or Ch lor o-
a ceta tes 4. To a suspension of the corresponding esters 3 or
(1 mmol) in a phosphate buffer (30 mL, 0.1 M, pH 7.0) was
4
added the lipase (30 mg PCL, or 80 mg CRL, or 140 mg CAL,
Novozym435), and the mixture was stirred at room temper-
ature. The conversion was followed by gas chromatography
Ack n ow led gm en t. Financial support by the Deut-
sche Forschungsgemeinschaft and the Fonds der Che-
mischen Industrie is gratefully acknowledged. We wish
to thank the Bayer AG, Leverkusen, Germany, the Novo
Nordisk A/S, Copenhagen, Denmark, and the Amano
Pharmaceutical Co., Ltd., Nagoya, J apan, for kind
donation of chemicals and enzymes, respectively.
(aliquots of 0.5 mL were taken and extracted with 1 mL of
diethyl ether, dried over magnesium sulfate, and analyzed).
After ca. 50% of conversion, the reaction mixture was extracted
with diethyl ether (3 × 15 mL). The combined ethereal extracts
were dried over magnesium sulfate, and the solvent was
evaporated. The remaining mixture of the acetates 3 or 4 and
the corresponding fluorohydrins 2 were separated by column
chromatography (silica gel, pentane/diethyl ether, 1:1), and the
enantiomeric excess (chiral GC, results are given in Table 1)
and the optical rotation were determined (Table 4, Supporting
Information).
Su p p or tin g In for m a tion Ava ila ble: 1H, 13C, and 19
F
NMR spectral data including assignments of the signals and
the EI mass spectral data of the acetates 3b and 3c and all
chloroacetates 4, respectively. Optical rotations and the re-
spective enantiomeric excesses of the enantiomers of 2-4.
This material is available free of charge via the Internet at
http://pubs.acs.org.
Im m obiliza tion of th e Lip a ses. According to ref 29, Celite
5
77 (2 g) was washed with water and phosphate buffer (0.1
M, pH 7.0) and subsequently added to a suspension of PCL or
CRL (0.5 g) in phosphate buffer (10 mL, 0.1 M, pH 7.0) and
stirred for 30 min. The buffer was removed by filtration, and
the solid was air-dried with occasionally mixing. The water
J O016331R
(29) Bianchi, D.; Chesti, P.; Battistel, E. J . Org. Chem. 1988, 53,
5531-5534.