Nitrile biotransformations for the synthesis of enantiomerically enriched Baylis-Hillman adducts.

Article abstract of DOI:10.1039/b209791e

Catalysed by the nitrile hydratase/amidase-containing Rhodococcus sp. AJ270 cells, a number of beta-aryl- and beta-alkyl- beta-hydroxy-alpha-methylenepropiononitriles (the Baylis-Hillman nitriles) 1 underwent hydrolysis under mild conditions to produce the corresponding enantiomerically enriched Baylis-Hillman amides 2 and acids 3. The enantioselectivity of the biotransformations was strongly determined by the steric effect of the substituents at the beta-position of the substrates. The protection of the free hydroxy of beta-phenyl-beta-hydroxy-alpha-methylenepropiononitrile 1a by methylation led to the enhancement of enantiocontrol of the biohydrolysis.

Full text of DOI:10.1039/b209791e

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Nitrile biotransformations for the synthesis of enantiomerically
enriched Baylis–Hillman adducts
Mei-Xiang Wang* and Yan Wu
Laboratory of Chemical Biology, Centre for Molecular Science, Institute of Chemistry,
Chinese Academy of Sciences, Beijing 100080, China. E-mail: mxwang@infoc3.icas.ac.cn
Received 8th October 2002, Accepted 14th November 2002
First published as an Advance Article on the web 23rd December 2002
Catalysed by the nitrile hydratase/amidase-containing Rhodococcus sp. AJ270 cells, a number of β-aryl- and β-alkyl-
β-hydroxy-α-methylenepropiononitriles (the Baylis–Hillman nitriles) 1 underwent hydrolysis under mild conditions
to produce the corresponding enantiomerically enriched Baylis–Hillman amides 2 and acids 3. The enantioselectivity
of the biotransformations was strongly determined by the steric effect of the substituents at the β-position of the
substrates. The protection of the free hydroxy of β-phenyl-β-hydroxy-α-methylenepropiononitrile 1a by methylation
led to the enhancement of enantiocontrol of the biohydrolysis.
Our previous study has revealed an interesting ortho-
substituent effect for the Rhodococcus sp. AJ270-catalysed
Introduction
hydrolysis of nitriles; the hydrolysis of acrylonitrile gave acrylic
acid without accumulation of acrylamide while methacrylo-
nitrile afforded a mixture of methacrylamide and methacrylic
acid in a short incubation time.11 We envisaged that by intro-
ducing a stereogenic center into the α-position of acrylonitrile,
the Baylis–Hillman nitrile, for example, the biotransformation
would give rise to the Baylis–Hillman amide. More importantly,
the amidase would kinetically resolve the amide and therefore
produce optically active Baylis–Hillman amide and acid. It
should be noted that the biotransformation of the Baylis–
Hillman nitriles differs greatly from those lipase-catalyzed
kinetic resolution of the secondary alcohol of the Baylis–
Hillman substrates,7 because in our case the stereogenic center
is remote from or β-positioned to the enzyme-reacting cyano
and amido function groups. To our knowledge, there is no such
study reported in literature.14
The reaction between electron-deficient alkenes and aldehydes
catalyzed by 1,4-diazabicyclo[2.2.2]octane (DABCO), well-
known as the Baylis–Hillman reaction, provides a direct entry
to synthetically versatile α-methylene-β-hydroxy carbonyl/
nitrile compounds.1,2 Despite its obvious utility, this base-
catalyzed reaction, however, suffers from a few drawbacks. For
example, the Baylis–Hillman reaction usually takes a very long
period of time under atmospheric pressure and some electron-
deficient alkenes do not effectively participate in the reaction.1a
It has been reported that whist acrylonitrile undergoes the reac-
tion readily under ambient conditions,3 acrylamide appears
unreactive.1a Furthermore, although the Baylis–Hillman reac-
tion involves the generation of a stereogenic center, the study of
asymmetric reactions has only met with mixed success so far.1b,4
Using chiral auxiliaries such as the Oppolzer camphor sultam
used recently by Leahy et al.5 and a camphor-derived hydrazide
developed later by Yang and Chen,6 efficient stereoselective
Baylis–Hillman reactions have been achieved towards
a
Results and discussion
number of aliphatic aldehydes. However, both chiral auxiliary
approaches showed low to no reactivity against α-branched
aliphatic aldehydes and, particularly, aromatic aldehydes.5,6
Moderate to excellent enantioselectivity has been reported from
the biocatalytic resolution of the secondary alcohol of the
Baylis–Hillman adducts.7 From the practical point of view,
almost no useful catalytic enantioselective Baylis–Hillman reac-
tion has been reported.1b,4
Since the successful industrial production of acrylamide
from the microbial hydration of acrylonitrile, there has been an
increasing interest in biotransformations of nitriles.8 It has been
known for decades that biotransformations of nitriles proceed
through either a direct transformation into the acids catalyzed
by a nitrilase or the nitrile hydratase-catalyzed hydration to the
amides followed by the hydrolysis to the acids by the action of
an amidase.8 Recent studies have also shown that nitrile-hydro-
lyzing enzymes and the amidases display enantiomeric dis-
criminations against nitrile and amide substrates, respectively,
and therefore enantioselective biotransformations of nitriles
have drawn much attention in recent years.8,9 Among the vari-
ous nitrile-hydrolyzing microorganisms reported, Rhodococcus
sp. AJ270, an isolate from a soil sample,10 appears to be a robust
and efficient nitrile hydratase/amidase-containing biocatalyst
able to hydrolyze nitriles in chemo-,11 regio-12 and enantio-
selective13 manners. Interest in the Baylis–Hillman reaction and
in the understanding of enzymes’ action and their synthetic
potential led us to undertake the current study.
We first examined the preparation of the Baylis–Hillman amide
from the biotransformation of α-methylene-β-hydroxy-β-
phenylpropiononitrile 1a. As we expected, Rhodococcus sp.
AJ270 efficiently converted 1a into the racemic α-methylene-β-
hydroxy-β-phenylpropionamide 2a in 90% yield under very
mild conditions.1a Complete hydrolysis could yield the racemic
Baylis–Hillman acid 3a, but it took weeks, which makes this
approach synthetically impractical. The slower conversion of
the amide 2a as we anticipated, however, allowed us to study the
stereochemistry of this biocatalytic reaction (Scheme 1).
As shown in Table 1, biotransformations of racemic 1a at
around 50% conversion led to a kinetic resolution, yielding
S-(ϩ)-α-methylene-β-hydroxy-β-phenylpropionamide 2a and
R-(Ϫ)-α-methylene-β-hydroxy-β-phenylpropionic acid14 3a
with enantiomeric excesses ranging from 31–80% (entries 1 to 3
in Table 1). Complete hydrolysis of optically active S-(ϩ)-α-
methylene-β-hydroxy-β-phenylpropionamide 2a (ee 63%) pro-
ceeded in 1 week with the aid of Rhodococcus sp. AJ270 to
afford almost quantitatively S-(ϩ)-α-methylene-β-hydroxy-β-
phenylpropionic acid 414 (ee 64%) (Scheme 2). The results indi-
cated clearly that the nitrile hydratase involved in the microbial
cells showed almost non-enantioselectivity against nitrile 1a
while the amidase exhibits R-enantioselection towards amide
2a. To examine the substituent effect of the aromatic ring on the
biotransformation reaction, a number of the Baylis–Hillman
nitriles 1b–j were prepared7,15 and fed to Rhodococcus sp.
T h i s j o u r n a l i s © T h e R o y a l S o c i e t y o f C h e m i s t r y 2 0 0 3
O r g . B i o m o l . C h e m . , 2 0 0 3 , 1, 5 3 5 – 5 4 0
535

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Table 1 Biotransformations of nitriles 1
Entry
Substrate
Ar
Conditionsa
2, yield (%)b
2, ee (%)c
3, yield (%)b
3, ee (%)c
Ed
1
2
3
4
5
6
7
8
9
10
11
12
13
14
1a
1a
1a
1a
1b
1c
1d
1e
1f
1g
1h
1i
1j
1j
C6H5
C6H5
C6H5
C6H5
4-MeO–C6H4
3-MeO–C6H4
2-MeO–C6H4
4-Me–C6H4
4-Cl–C6H4
3-Cl–C6H4
2-Cl–C6H4
Et
3 mmol, 24 h
1 mmol, 24 h
1 mmol, 36 h
1 mmol, 48 h
1 mmol, 24 h
1 mmol, 48 h
1 mmol, 72 h
1 mmol, 72 h
0.5 mmol, 24 h
0.5 mmol, 48 h
0.5 mmol, 12 h
1 mmol, 45 min
3 mmol, 8 h
90
59
46
29
43
48
50
45
45
49
50
44
43
64
0
33
63
80
41
81
79
41
49
53
78
0
—
35
47
63
52
45
44
45
49
45
48
47
51
26
—
55
45
31
27
75
70
45
39
38
80
0
—
4.7
4.8
4.2
2.5
17
13
3.9
3.6
3.6
21
—
6.4
4.0
Me2CH
Me2CH
61
19
56
54
3 mmol, 10 he
a The substrate was incubated with Rhodococcus sp. AJ270 cells (2 g wet weight) in phosphate buffer (pH 7.0, 10 mM, 50 ml). The reaction conditions
were not optimized. b Isolated yield. c Determined by HPLC analysis using a Chiralcel OD or OJ column. d See ref. 17. e Acetone (3 ml) was added.
reaction and lower enantioselectivity of biotransformations of
alkyl-containing Baylis–Hillman nitriles 1i and 1j in com-
parison to aryl-bearing nitriles 1a–h suggested the sterically
demanding nature of the enzymes.
To understand the role of the hydroxy group played in
biotransformation, we protected it by methylation and the
resulting substrate 5 was then subjected to biohydrolysis
(Scheme 3). Compared to the reaction of the parent nitriles, the
Scheme 1 Biotransformations of nitriles 1.
Scheme 2 Bioconversion of S-(ϩ)-amide 2a into S-(ϩ)-acid 4.
AJ270. In all cases of nitriles 1b–h derived from aromatic alde-
hydes, the reaction gave optically active S-(ϩ)-amide 2b–h and
R-(Ϫ)-acid 3b–h. It is interesting to note that, although the
electronic nature of the substituent affected the enantiomeric
excesses of the products, it was the substitution pattern that
mainly governed the reaction enantioselectivity. For example,
all substrates bearing a para-substituent such as 1d, 1e and 1h
resulted in modest enantioselectivity with enantiomeric ratio16
E<4, whereas the ortho-substituted analogs 1b and 1f gave high
enantioselectivity with E being 21 and 13, respectively. Good
enantioselectivity (E 17) was also obtained for 3-methoxy-
benzaldehyde-derived Baylis–Hillman nitrile 1g, but not for
3-chlorine substituted substrate 1c. The highly preferential
enantioselection for the ortho-substituted aromatic substrates in
this study is intriguing, as for other α-substituted phenyl-
acetonitriles and amides it is always the para-substitution on
the aromatic ring that lead to the increase of enantio-
selectivity.9,13 This may be due to the fact that in 1 or 2, the
aromatic ring is remote from or β-positioned to the cyano or
amido functional group. The nitriles 1i–j prepared form ali-
phatic aldehydes underwent a rapid hydrolysis under the similar
reaction conditions. When the reaction was quenched at around
50% conversion of the amide, 1i gave optically inactive products
2i and 3i in good yields while 1j yielded (Ϫ)-2j and (ϩ)-3j with
moderate enantiomeric excesses (entries 12–14). The faster
Scheme
3
Biotransformations of O-methylated Baylis–Hillman
nitriles
hydrolysis rate of all methyl protected nitriles 5 decreased.
Intriguingly, however, the enantioselectivity of the reaction of
5a was greatly enhanced, with E improving from 4.8 to 12, while
the alkyl-substituted analogous substrates 5i and 5j did not give
either improved or worsened enantiomeric excesses (Table 2).
The outcomes suggest that it is the steric effect rather than the
electronic or hydrogen bonding effect of the hydroxy substitu-
ent at stereogenic positions that determines the enantio-
selectivity of the enzymatic reaction. In other words, the
biotransformation of analogous α,β-unsaturated nitriles bear-
ing substituents other than hydroxy or alkoxy group would also
take place in an enantioselective manner. Furthermore, this
observation may open a new avenue to improve the enantio-
selective efficiency of the biotransformation of the Baylis–
Hillman nitriles by masking the hydroxy using other protecting
groups.17
In conclusion, we have shown that Rhodococcus sp. AJ270 is
able to catalyze the hydrolysis of the Baylis–Hillman nitriles
under mild conditions. Though the stereogenic center is remote
or β-positioned to the cyano or amido functional group, the
amidase involved in microbial cells still shows modest to good
R-enantioselectivity. We have also found that the enantio-
O r g . B i o m o l . C h e m . , 2 0 0 3 , 1, 5 3 5 – 5 4 0
536

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Table 2 Biotransformations of nitriles 5
Entry
Substrate
Ar
Conditionsa
6, yield (%)b
6, ee (%)c
7, yield (%)b
7, ee (%)c
Ed
1
2
3
4
5a
5a
5i
C6H5
C6H5
Et
1 mmol, 72 h
1 mmol, 168 he
1 mmol, 7.5 h
1 mmol, 72 h
S-(ϩ)-6a (47)
S-(ϩ)-6a (57)
( )-6i (46)
53
38
0
R-(Ϫ)-7a (43)
R-(Ϫ)-7a (34)
( )-7i (44)
77
82
0
12
14
—
5j
Me2CH
(Ϫ)-6j (47)
60
(ϩ)-7j (44)
56
6.4
a The substrate was incubated with Rhodococcus sp. AJ270 cells (2 g wet weight) in phosphate buffer (pH 7.0, 10 mM, 50 ml). The reaction conditions
were not optimized. b Isolated yield. c Determined by HPLC analysis using a Chiralcel OD or OJ column. d See ref. 17 e Acetone (2 ml) was added.
selectivity of the reaction is influenced by the steric factor of the
substituent at the stereogenic center and it can be improved by
engineering the Baylis–Hillman nitrile substrate with a methyl
protection group at the hydroxy group. Our study has provided
a new approach for the preparation of enantiomerically
enriched R-(Ϫ)-β-aryl-β-hydroxy-α-methylenepropionic acids
and their S-(ϩ)-amides which are hardly accessible by other
chemical5,6 and enzymatic7 methods. Biotransformation of
various Baylis–Hillman nitriles and improvement of enantio-
selectivity utilizing protecting group strategy17 is being actively
studied in this laboratory.
3-Methoxy-4-methyl-2-methylenepentanenitrile 5j
(65%) was obtained as a colorless oil; νmax(KBr disc)/cmϪ1 2224;
δH(200 MHz; CDCl3; Me4Si) 6.11 (1 H, s), 5.89 (1 H, s), 3.99
(1 H, s), 3.33 (3 H, s), 2.01–1.84 (1 H, m), 0.98 (3 H, J 7.2) and
0.92 (3 H, J 7.0); δC(75 MHz; CDCl3; Me4Si) 17.9, 18.6, 31.8,
57.3, 87.7, 117.0, 123.5 and 132.3; m/z (EI) 124 (Mϩ Ϫ 15, 3)
and 97 (100).
General procedure for the biotransformations of nitriles
To an Erlenmeyer flask (100 ml) with a screw cap were added
Rhodococcus sp. AJ270 cells10,11 (2 g wet weight) and potassium
phosphate buffer (0.1 M, 50 ml) and the resting cells were acti-
vated at 30 ЊC for 30 min with orbital shaking. Racemic nitriles
were added in one portion to the flask and the mixture was
incubated at 30 ЊC with the use of an orbital shaker (200 rpm).
The reaction, monitored by TLC, was quenched after a speci-
fied period of time (see Tables 1 and 2) by removing the biomass
throughCelite pad filtration. The resulting aqueous solution
was basified to pH 12 with aqueous NaOH (2 M). Extraction
with ethyl acetate gave, after drying and concentration, the
amides and unconverted nitriles. Separation of amide and
nitrile was effected by column chromatography. The aqueous
solution was then acidified using aqueous HCl (2 M) to pH 2
and extracted with ethyl acetate. Acid was obtained after
removal of the solvent. All products were characterized by their
spectral data and comparison of the melting points and optical
rotary power with that of the known compounds or by full
characterization.
Experimental
Both melting points, which were determined using a Reichert
Kofler hot-stage apparatus, and boiling points are uncorrected.
IR spectra were obtained on a Perkin-Elmer 782 instrument as
liquid films or KBr discs. NMR spectra were recorded on
Bruker AM 300 and Varian Unity 200 spectrometers. Chemical
shifts are reported in ppm and coupling constants are given
in hertz. Mass spectra were measured on an AEI MS-50
mass spectrometer and microanalyses were carried out by the
Analytical Laboratory of the Institute.
Polarimetry was carried out using an Optical Activity AA-
10R polarimeter and the measurements were made at the
sodium D-line with a 5 cm pathlength cell. Concentrations (c)
are given in g (100 ml)Ϫ1. The enantiomeric excesses of
all compounds were obtained with a Shimadzu LC-10AVP
HPLC system, except for compounds 6i,j and 7j for which the
enantiomeric excess values were determined by chiral GC
analysis. Starting nitriles 1 were prepared according to the
literature.7,15
Enzymatic hydrolysis of 3-hydroxy-2-methylene-3-phenyl-
propiononitrile 1a
3S-(ϩ)-3-Hydroxy-2-methylene-3-phenylpropionamide
2a
General procedure for the preparation of O-methylated Baylis–
(46%) was obtained as white solids (Found: C, 67.63; H, 6.21; N
8.07. C10H11NO2 requires C, 67.78; H, 6.26; N, 7.90%); mp
94–96 ЊC; [α]2D5 ϩ15.94 (c 1.38, CH3OH); ee 63% (HPLC
analysis); νmax(KBr disc)/cmϪ1 3380, 3185, 1660, 1630 and 1605;
δH(200 MHz; DMSO-d6; Me4Si) 7.42 (1 H, s), 7.34–7.20 (5 H,
m, Ar–H), 6.96 (1 H, s), 5.78 (1 H, s), 5.58 (1 H, s) and 5.48
(1 H, s); δC(75 MHz; DMSO-d6; Me4Si) 71.4, 117.8, 127.1,
127.4, 128.3, 143.6, 147.8 and 169.1; m/z (EI) 177 (Mϩ, 18%),
176 (46), 160 (21), 132 (30), 115 (19) and 105 (100). Chiral
HPLC analysis of the racemic amide using a Chiralcel OD
column with a mixture of hexane and propan-2-ol (90:10) as
the mobile phase at a flow rate of 0.8 ml minϪ1 gave tϩ = 28.6
min and tϪ = 23.7 min.
Hillman nitriles 5
A mixture of the Baylis–Hillman nitrile 1 (10 mmol), methyl
iodide (40 mmol) and Ag2O (10 mmol) was stirred at room
temperature for 24 h. Ether (30 ml) was added and the mixture
was well stirred and filtered. After removal of the solvent, the
residue was subjected to flash chromatography using a silica gel
column with dichloromethane as the eluent.
3-Methoxy-2-methylene-3-phenylpropiononitrile 5a
(77%) was obtained as a colorless oil (Found: C, 75.89; H, 6.42;
N, 8.42. C11H11NO requires C, 75.89; H, 6.40; N, 8.09%);
νmax(KBr disc)/cmϪ1 2226; δH(200 MHz; CDCl3; Me4Si)
7.37 (5 H, s), 6.01 (2 H, d, J 3.8), 4.75 (1 H, s) and 3.73 (3 H, s);
δC(75 MHz; CDCl3; Me4Si) 57.0, 83.0, 116.8, 125.0, 126.9,
128.8, 130.8 and 137.3; m/z (EI) 173 (Mϩ, 4%), 142 (6) and
121 (100).
3R-3-Hydroxy-2-methylene-3-phenylpropionic acid14 3a
(47%) was obtained as white solids (Found: C, 67.37; H, 5.72.
C10H10O3 requires C, 67.41; H, 5.66%); mp 80–81 ЊC (lit.14 79
ЊC); [α]2D5 Ϫ48.15 (c 0.5, CH3OH) {lit.14 [α]2D5 Ϫ23.2 (c 1.05,
CHCl3)}; ee 45% (HPLC analysis); νmax(KBr disc)/cmϪ1 2700–
3352, 1686 and 1630; δH(200 MHz; CDCl3; Me4Si) 7.25–7.37
(5 H, m, Ar–H), 6.48 (1 H, s), 5.95 (1 H, s) and 5.56 (1 H, s);
δC(75 MHz; CDCl3; Me4Si) 72.8, 126.7, 128.1, 128.5, 128.6,
140.8, 141.2 and 171.2; m/z (EI) 178 (Mϩ, 39%), 177 (39), 160
(13), 132 (43), 115 (29) and 105 (100). Chiral HPLC analysis of
the racemic acid using a Chiralcel OJ column with a mixture of
hexane, propan-2-ol and H3PO4(90:10:0.1) as the mobile phase
3-Methoxy-2-methylenepentanenitrile 5i
(60%) was obtained as a colorless oil; νmax(KBr disc)/cmϪ1 2225;
δH(200 MHz; CDCl3; Me4Si) 6.09 (1 H, s), 5.94 (1 H, s), 3.62
(1 H, t, J 7.4), 3.34 (1 H, s), 1.83–1.67 (2 H, m) and 0.95 (3 H, t,
J 7.4); δC(75 MHz; CDCl3; Me4Si) 9.3, 27.1, 56.8, 83.3, 116.7,
124.2 and 131.7; m/z (EI) 125 (Mϩ, 5%) and 96 (100).
O r g . B i o m o l . C h e m . , 2 0 0 3 , 1, 5 3 5 – 5 4 0
537

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at a flow rate of 0.8 ml minϪ1 gave tϩ = 36.8 min and tϪ = 20.8
min.
H, 6.38; N, 6.63. C11H13NO3 requires C, 63.76; H, 6.32; N;
6.76%); mp 156–156 ЊC; [α]2D5 ϩ54.24 (c 0.88, CH3OH); ee 79%
(HPLC analysis); νmax(KBr disc)/cmϪ1 3383, 3339, 1668, 1621
and 1612; δH(300 MHz; DMSO-d6; Me4Si) 7.43 (1 H, s), 7.26–
7.19 (2 H, m), 6.95–6.87 (2 H, m), 5.76 (1 H, s), 5.73 (1 H, s),
5.28 (1 H, s) and 3.73 (3 H, s); δC(75 MHz; DMSO-d6; Me4Si)
56.1, 65.7, 111.5, 118.7, 120.8, 128.0, 129.1, 131.6, 147.7, 157.1
and 169.8; m/z (EI) 207 (Mϩ, 5%), 206 (17), 189 (22), 176 (15),
137 (45) and 135 (100). Chiral HPLC analysis of the racemic
amide using a Chiralcel OB column with a mixture of hexane
and propan-2-ol (90:10) as the mobile phase at a flow rate of 0.8
ml minϪ1 gave tϩ = 26.9 min and tϪ = 34.3 min.
Enzymatic hydrolysis of 3-hydroxy-3-(4-methoxyphenyl)-2-
methylenepropiononitrile 1b
3S-(ϩ)-3-Hydroxy-3-(4-methoxyphenyl)-2-methylenepropion-
amide 2b (52%) was obtained as white solids (Found: C, 63.62;
H, 6.21; N, 6.63. C11H13NO3 requires C, 63.76; H, 6.32; N;
6.76%); mp 104–106 ЊC; [α]2D5 ϩ13.79 (c 1.0, CH3OH); ee 41%
(HPLC analysis); νmax(KBr disc)/cmϪ1 3379, 3181, 1659 and
1610; δH(300 MHz; DMSO-d6; Me4Si) 7.40 (1 H, s), 7.17 (2 H,
d, J 8.7), 6.93 (1 H, s), 6.83 (2 H, d, J 8.7), 5.74 (1 H, s), 5.56
(1 H, s), 5.41 (1 H, s), 3.70 (3 H, s); δC(75 MHz; DMSO-d6;
Me4Si) 55.8, 71.4, 114.0, 117.7, 128.7, 135.9, 148.4, 159.0 and
169.5; m/z (EI) 207 (Mϩ, 7%), 206 (9), 190 (18), 189 (18), 146
(14) and 135 (100). Chiral HPLC analysis of the racemic amide
using a Chiralcel OJ column with a mixture of hexane, propan-
2-ol and H3PO4 (90:10:0.1) as the mobile phase at a flow rate of
0.8 ml minϪ1 gave tϩ = 46.0 min and tϪ = 57.0 min.
3R-(Ϫ)-3-Hydroxy-3-(2-methoxyphenyl)-2-methylene-
propionic acid 3d (44%) was obtained as white solids; mp 81–
82; [α]2D5 Ϫ55.27 (c 2.75, CH3OH); ee 70% (HPLC analysis);
νmax(KBr disc)/cmϪ1 2750–3500 and 1703 (C᎐O); δ (300 MHz;
᎐
H
CDCl3; Me4Si) 7.34–7.26 (2 H, m), 7.00–6.89 (2 H, m), 6.46
(1 H, s), 5.86 (1 H, s), 5.82 (1 H, s) and 3.85 (3 H, s); δC(75 MHz;
CDCl3; Me4Si) 55.4, 68.1, 110.6, 120.8, 127.7, 128.3, 128.6,
129.1, 140.6, 156.6 and 171.6; m/z (EI) 207.0665 (C11H12O4
requires 207.0663), 190 (18), 162 (33), 147 (24), 137 (42) and 135
(100). Chiral HPLC analysis of the racemic acid using a Chiral-
cel OD column with a mixture of hexane, propan-2-ol and
H3PO4 (90:10:0.1) as the mobile phase at a flow rate of 0.8 ml
minϪ1 gave tϩ = 12.9 min and tϪ = 16.1 min.
3R-(Ϫ)-3-Hydroxy-3-(4-methoxyphenyl)-2-methylene-
propionic acid 3b (43%) was obtained as white solids (Found:
C, 63.50; H 5.81. C11H12O4 requires C, 63.45; H, 5.81%); mp 88–
89 ЊC; [α]2D5 Ϫ27.98 (c 1.93 CH3OH); ee 27% (HPLC analysis);
νmax(KBr disc)/cmϪ1 2600–3278, 1691 and 1618; δH(300 MHz;
CDCl3; Me4Si) 7.30 (2 H, d, J 8.7), 6.89 (2 H, d, J 8.7), 6.47
(1 H, s), 5.97 (1 H, s), 5.41 (1 H, s) and 3.81 (3 H, s); δC(75 MHz;
CDCl3; Me4Si) 55.6, 72.7, 114.2, 128.3, 128.5, 133.4, 141.7,
159.7 and 171.1; m/z (EI) 208 (Mϩ, 13%), 190 (24), 162 (14) and
146 (100). Chiral HPLC analysis of the racemic acid using a
Chiralcel OJ column with a mixture of hexane, propan-2-ol and
H3PO4 (90:10:0.1) as the mobile phase at a flow rate of 0.8 ml
minϪ1 gave tϩ = 61.3 min and tϪ = 42.3 min.
Enzymatic hydrolysis of 3-hydroxy-2-methylene-3-(4-methyl-
phenyl)propiononitrile 1e
3S-(ϩ)-3-Hydroxy-2-methylene-3-(4-methylphenyl)propion-
amide 2e (45%) was obtained as white solids (Found: C, 68.83;
H, 6.80; N, 7.28. C11H13NO2 requires C, 69.09; H, 6.85; N,
7.32%); mp 117–118 ЊC; [α]2D5 ϩ16.28 (c 0.86, CH3OH); ee 41%
(HPLC analysis); νmax(KBr disc)/cmϪ1 3393, 3191, 1659 and
1618; δH(300 MHz; DMSO-d6; Me4Si) 7.39 (1 H, s), 7.15 (2 H,
d, J 7.8), 7.08 (2 H, d, J 7.8), 6.93 (1 H, s), 5.75 (1 H, s), 5.59
(1 H, br s), 5.55 (1 H, s), 5.42 (1 H, s) and 3.25 (3 H, s);
δC(75 MHz; DMSO-d6; Me4Si) 21.5, 71.7, 118.0, 127.5, 129.3,
136.8, 140.9, 148.3 and 169.6; m/z (EI) 191 (Mϩ, 9%), 190 (26),
174 (18), 146 (19) and 119 (100). Chiral HPLC analysis of the
racemic amide using a Chiralcel OD column with a mixture of
hexane and propan-2-ol (90:10) as the mobile phase at a flow
rate of 0.8 ml minϪ1 gave tϩ = 27.5 min and tϪ = 25.4 min.
3R-(Ϫ)-3-Hydroxy-2-methylene-3-(4-methylphenyl)propi-
onic acid 3e (45%) was obtained as white solids (Found: C,
68.61; H, 6.22. C11H12O3 requires C, 68.74; H, 6.29%); mp 91–
92 ЊC; [α]2D5 Ϫ55.71 (c 1.79, CH3OH); ee 45% (HPLC analysis);
νmax(KBr disc)/cmϪ1 2759–3394, 1716, 1673 and 1623; δH(300
MHz; CDCl3; Me4Si) 7.26 (2 H, d, J 7.8), 7.17 (2 H, d, J 7.8),
6.48 (1 H, s), 5.98 (1 H, s), 5.55 (1 H, s) and 2.35 (3 H, s);
δC(75 MHz; CDCl3; Me4Si) 21.0, 72.5, 126.4, 128.2, 129.0,
137.6, 137.7, 141.1 and 171.1; m/z (EI) 192 (Mϩ, 21%), 177 (26),
174 (28), 159 (8), 146 (30), 130 (51), 129 (43), 128 (33) and 119
(100). Chiral HPLC analysis of the racemic acid using a Chiral-
cel OJ column with a mixture of hexane, propan-2-ol and
H3PO4 (90:10:0.1) as the mobile phase at a flow rate of 0.8 ml
minϪ1 gave tϩ = 28.9 min and tϪ = 17.7 min.
Enzymatic hydrolysis of 3-hydroxy-3-(3-methoxyphenyl)-2-
methylenepropiononitrile 1c
3S-(ϩ)-3-Hydroxy-3-(3-methoxyphenyl)-2-methylenepropion-
amide 2c (48%) was obtained as white solids (Found: C, 64.01;
H, 6.27; N, 6.74. C11H13NO3 requires C, 63.76; H, 6.32; N;
6.76%); mp 93.5–94.5 ЊC; [α]2D5 ϩ12.96 (c 1.23, CH3OH); ee 81%
(HPLC analysis); νmax(KBr disc)/cmϪ1 3389, 3214, 1630 and
1599; δH(300 MHz; DMSO-d6; Me4Si) 7.41 (1 H, s), 7.18 (1 H, t,
J 8.0), 6.95 (1 H, s), 6.85–6.74 (3 H, m), 5.75 (1 H, s), 5.70 (1 H,
br s), 5.55 (1 H, s), 5.43 (1 H, s) and 3.85 (3 H, s); δC(75 MHz;
DMSO-d6; Me4Si) 55.7, 71.6, 112.9, 113.2, 118.2, 119.8, 129.7,
145.6, 148.1, 159.8 and 169.5; m/z (EI) 207 (Mϩ, 11%), 206 (19),
190 (19), 189 (23), 188 (10), 187 (19), 185 (18), 162 (14), 160 (15)
and 135 (100). Chiral HPLC analysis of the racemic amide
using a Chiralcel OD column with a mixture of hexane and
propan-2-ol (90:10) as the mobile phase at a flow rate of 0.8 ml
minϪ1 gave tϩ = 48.6 min and tϪ = 36.8 min.
3R-(Ϫ)-3-Hydroxy-3-(4-methoxyphenyl)-2-methylene-
propionic acid 3c (45%) was obtained as an oil; [α]2D5 Ϫ76.6
(c 0.23, CH3OH); ee 75% (HPLC analysis); νmax(KBr disc)/cmϪ1
2750–3500, 1702 and 1601; δH(300 MHz; CDCl3; Me4Si) 7.27
(1 H, t, J 8.1), 7.26 (1 H, s), 6.96–6.83 (2 H, m), 6.49 (1 H, s),
5.96 (1 H, s), 5.55 (1 H, s) and 3.81 (3 H, s); δC(75 MHz;
DMSO-d6; Me4Si) 55.2, 72.7, 112.2, 113.5, 119.0, 128.7, 129.6,
141.1, 142.5, 159.6 and 171.2; m/z (EI) 207.0664 (C11H12O4
requires 207.0663), 190 (36), 162 (32) and 135 (100). Chiral
HPLC analysis of the racemic acid using a Chiralcel OJ column
with a mixture of hexane, propan-2-ol and H3PO4 (90:10:0.1) as
the mobile phase at a flow rate of 0.8 ml minϪ1 gave tϩ = 34.8
min and tϪ = 26.7 min.
Enzymatic hydrolysis of 3-(4-chlorophenyl)-3-hydroxy-2-
methylenepropiononitrile 1f
3S-(ϩ)-3-(4-Chlorophenyl)-3-hydroxy-2-methylenepropion-
amide 2f (45%) was obtained as white solids (Found: C, 56.41;
H, 5.02; N, 6.63%. C10H10NO2Cl requires C, 56.75; H, 4.76; N,
6.62%); mp 127–129 ЊC; [α]2D5 ϩ13.89 (c 0.72, CH3OH); ee 49%
(HPLC analysis); νmax(KBr disc)/cmϪ1 3390, 3200, 1660 and
1620; δH(300 MHz; DMSO-d6; Me4Si) 7.45 (1 H, s), 7.33 (2 H,
d, J 8.6), 7.29 (2 H, d, J 8.6), 6.97 (1 H, s), 5.79 (1 H, s), 5.60
(1 H, s) and 5.46 (1 H, s); δC(75 MHz; DMSO-d6; Me4Si) 70.7,
118.0, 128.3, 129.0, 131.9, 142.7, 147.5 and 168.9; m/z (EI)
213 (10), 212 (28), 211 (Mϩ, 31%), 210 (82), 196 (14), 194 (45),
Enzymatic hydrolysis of 3-hydroxy-3-(2-methoxyphenyl)-2-
methylenepropiononitrile 1d
3S-(ϩ)-3-Hydroxy-3-(2-methoxyphenyl)-2-methylenepropion-
amide 2d (50%) was obtained as white solids (Found: C, 63.65;
O r g . B i o m o l . C h e m . , 2 0 0 3 , 1, 5 3 5 – 5 4 0
538

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168 (25), 166 (76), 141 (50) and 139 (100). Chiral HPLC analy-
sis of the racemic amide using a Chiralcel OD column with a
mixture of hexane and propan-2-ol (90:10) as the mobile phase
at a flow rate of 0.8 ml minϪ1 gave tϩ = 28.3 min and tϪ = 25.2
min.
3R-(Ϫ)-3-(4-Chlorophenyl)-3-hydroxy-2-methylenepropionic
acid 3f (49%) was obtained as an oil; [α]2D5 Ϫ26.67 (c 0.22,
CH3OH); ee 39% (HPLC analysis); νmax(KBr disc)/cmϪ1 2750–
3500, 1703 and 1631; δH(300 MHz; CDCl3; Me4Si) 7.32 (4 H, s),
6.49 (1 H,s), 5.97 (1 H,s) and 5.54 (1 H, s); δC(75 MHz; CDCl3;
Me4Si) 72.2, 128.1, 128.7, 128.9, 133.8, 139.3, 140.9 and 171.1;
m/z (EI) 214 (7), 213 (11), 211.0170 (C10H9O3Cl requires
211.0167), 211 (25), 194 (18), 177 (8), 166 (39) and 139 (100).
Chiral HPLC analysis of the racemic acid using a Chiralcel OJ
column with a mixture of hexane, propan-2-ol and H3PO4
(90:10:0.1) as the mobile phase at a flow rate of 0.8 ml minϪ1
gave tϩ = 17.0 min and tϪ = 13.5 min.
138.3, 140.4 and 171.6; m/z (EI) 214 (10), 213 (23), 211.0169
(C10H9O3Cl requires 211.0167), 211 (60), 177 (81), 159 (45), 141
(73), 139 (75), 131 (41) and 77 (100). Chiral HPLC analysis of
the racemic acid using a Chiralcel OJ column with a mixture of
hexane, propan-2-ol and H3PO4 (90:10:0.1) as the mobile phase
at a flow rate of 0.8 ml minϪ1 gave tϩ = 27.1 min and tϪ = 13.8
min.
Enzymatic hydrolysis of 3-hydroxy-2-methylenepentanenitrile 1i
( )-3-Hydroxy-2-methylenepentanamide 2i (44%) was obtained
as white solids (Found: C, 57.31; H, 8.51; N, 10.70. C6H11NO2
requires C, 57.80; H, 8.58; N, 10.84%); mp 53–54 ЊC; [α]2D5
0
(c 0.4, CH3OH); ee 0% (HPLC analysis); νmax(KBr disc)/cmϪ1
3382, 3193, 1658, 1629 and 1604; δH(300 MHz; DMSO-d6;
Me4Si) 7.47 (1 H, s), 7.03 (1 H, s), 5.69 (1 H, s), 5.46 (1 H, s),
4.93 (1 H, d, J 5.1), 4.26 (1 H, t, J 6.7), 1.58–1.28 (2 H, m) and
0.82 (3 H, t, J 7.4); δC(75 MHz; DMSO-d6; Me4Si) 10.3, 29.3,
70.5, 117.2, 148.3 and 169.7; m/z (EI) 100 (Mϩ Ϫ 29, 100) and
83 (86). Chiral HPLC analysis of the racemic amide using a
Chiralcel OD column with a mixture of hexane and propan-2-
ol (90:10) as the mobile phase at a flow rate of 0.8 ml minϪ1 gave
tϩ = 16.3 min and tϪ = 14.6 min.
Enzymatic hydrolysis of 3-(3-chlorophenyl)-3-hydroxy-2-
methylenepropiononitrile 1g
3S-(ϩ)-3-(3-Chlorophenyl)-3-hydroxy-2-methylenepropion-
amide 2g (45%) was obtained as white solids (Found: C, 56.76;
H, 4.78; N, 6.58. C10H10NO2Cl requires C, 56.75; H, 4.76; N,
6.62%); mp 103.5–104 ЊC; [α]2D5 ϩ11.35 (c 0.7, CH3OH); ee 53%
(HPLC analysis); νmax(KBr disc)/cmϪ1 3358, 3280, 3163, 1683
and 1594; δH(300 MHz; DMSO-d6; Me4Si) 7.49 (1 H, s), 7.34–
7.22 (4 H, m), 7.00 (1 H, s), 5.90 (1 H, br s), 5.85 (1 H, s), 5.63
(1 H, s) and 5.47 (1 H, s); δC(75 MHz; DMSO-d6; Me4Si) 70.8,
118.2, 125.9, 126.8, 127.3, 130.3, 133.1, 146.3, 147.2 and 168.8;
m/z (EI) 213 (2), 212 (9), 211 (Mϩ, 7%), 210 (26), 193 (22), 166
(25), 141 (67) and 139 (100). Chiral HPLC analysis of the
racemic amide using a Chiralcel OD column with a mixture of
hexane and propan-2-ol (90:10) as the mobile phase at a flow
rate of 0.8 ml minϪ1 gave tϩ = 26.9 min and tϪ = 23.5 min.
3R-(Ϫ)-3-(3-Chlorophenyl)-3-hydroxy-2-methylenepropionic
acid 3g (47%) was obtained as an oil; [α]2D5 Ϫ35.9 (c 1.56,
CH3OH); ee 38% (HPLC analysis); νmax(KBr disc)/cmϪ1 2750–
3500 and1700; δH(300 MHz; CDCl3; Me4Si) 7.39 (1 H, br s),
7.29 (4 H, s), 6.52 (1 H, s), 5.99 (1 H, s) and 5.55 (1 H, s); δC(75
MHz; CDCl3; Me4Si) 72.5, 125.2, 127.1, 128.5, 129.5, 130.1,
134.7, 141.0, 143.2 and 171.3; m/z (EI) 214 (7), 213 (9), 211.0169
(C10H9O3Cl requires 211.0167), 211 (21), 194 (16), 177 (17), 168
(16), 166 (38), 141 (46) and 139 (100). Chiral HPLC analysis of
the racemic acid using a Chiralcel OK column with a mixture
of hexane and propan-2-ol (90:10) as the mobile phase at a flow
rate of 0.2 ml minϪ1 gave tϩ = 42.1 min and tϪ = 46.9 min.
( )-3-Hydroxy-2-methylenepentanoic acid 3i (47%) was
obtained as an oil; [α]2D5 0 (c 1.55, CH3OH); ee 0% (HPLC analy-
sis); νmax(KBr disc)/cmϪ1 2500–3427, 1698 and 1629; δH(300
MHz; CDCl3; Me4Si) 7.28 (2 H, br s), 6.39 (1 H, s), 5.91 (1 H,
s), 4.38 (1 H, t, J 6.6), 1.78–1.62 (2 H, m) and 0.95 (3 H, t, J 7.4);
δC(75 MHz; CDCl3; Me4Si) 9.9, 28.8, 72.6, 127.4, 141.3 and
170.9; m/z (EI) 129.0557 (C6H10O3 requires 129.0557), 112
(Mϩ Ϫ 18, 12), 101 (45) and 83 (100). Chiral HPLC analysis
of the racemic acid using a Chiralcel OJ column with a mixture
of hexane, propan-2-ol and H3PO4 (100:2:0.1) as the mobile
phase at a flow rate of 0.8 ml minϪ1 gave t1 = 33.0 min and
t2 = 37.0 min.
Enzymatic hydrolysis of 3-hydroxy-2-methylene-4-methyl-
pentanenitrile 1j
(Ϫ)-3-Hydroxy-2-methylene-4-methylpentanamide 2j (43%)
was obtained as white solids (Found: C, 58.92; H, 8.86; N, 9.93.
C7H13NO2 requires C, 58.72; H, 9.15; N, 9.78%); mp 123–
124 ЊC; [α]2D5 Ϫ10.17 (c 3.0, CH3OH); ee 61% (HPLC analysis);
νmax(KBr disc)/cmϪ1 3320, 3170, 1680 and 1610; δH(200 MHz;
DMSO-d6; Me4Si) 7.41 (1 H, s), 6.95 (1 H, s), 5.70 (1 H, s)
5.42 (1 H, s), 4.81 (1 H, br s), 4.13 (1 H, d, J 4.8), 1.79–1.63 (1
H, m), 0.84 (3 H, d, J 6.6) and 0.77 (3 H, d, J 7.0); δC(75 MHz;
DMSO-d6; Me4Si) 17.0, 20.0, 32.2, 74.2, 117.9, 147.7 and 170.1;
m/z (EI) 125 (Mϩ Ϫ 18, 8), 101 (43), 100 (100) and 83 (59).
Chiral HPLC analysis of the racemic amide using a Chiralcel
OD column with a mixture of hexane and propan-2-ol (90:10)
as the mobile phase at a flow rate of 0.8 ml minϪ1 gave tϩ = 16.3
min and tϪ = 14.6 min.
Enzymatic hydrolysis of 3-(2-chlorophenyl)-3-hydroxy-2-
methylenepropiononitrile 1h
3S-(ϩ)-3-(2-chlorophenyl)-3-hydroxy-2-methylenepropion-
amide 2h (50%) was obtained as white solids (Found: C, 57.04;
H, 4.70; N, 6.63. C10H10NO2Cl requires C, 56.75; H, 4.76; N,
6.62%); mp 128–130 ЊC; [α]2D5 ϩ46.32 (c 0.95, CH3OH); ee 78%
(HPLC analysis); νmax(KBr disc)/cmϪ1 3313, 3200, 1672 and
1595; δH(300 MHz; DMSO-d6; Me4Si) 7.52 (1 H, s), 7.39–7.21
(4 H, m), 6.97 (1 H, s), 5.79 (2 H, s), 5.69 (1 H, br s) and 5.27
(1 H, s); δC(75 MHz; DMSO-d6; Me4Si) 67.8, 118.8, 127.2,
128.8, 129.1, 129.4, 132.7, 140.6, 146.6 and 169.0; m/z (EI) 212
(6), 211 (Mϩ, 3%), 210 (18), 193 (19), 176 (96), 174 (28), 143
(22), 141 (91), 139 (83) and 77 (100). Chiral HPLC analysis of
the racemic amide using a Chiralcel OD column with a mixture
of hexane and propan-2-ol (90:10) as the mobile phase at a flow
rate of 0.8 ml minϪ1 gave tϩ = 34.1 min and tϪ = 38.5 min.
3R-(Ϫ)-3-(2-Chlorophenyl)-3-hydroxy-2-methylenepropionic
acid 3h (48%) was obtained as an oil; [α]2D5 Ϫ45.71 (c 0.35,
CH3OH); ee 80% (HPLC analysis); νmax(KBr disc)/cmϪ1 2750–
3500 and 1702; δH(300 MHz; CDCl3; Me4Si) 7.59–7.26 (4 H,
m), 6.49 (1 H, s), 6.00 (1 H, s) and 5.70 (1 H, s); δC(75 MHz;
CDCl3; Me4Si) 69.1, 127.4, 128.4, 129.5, 129.8, 129.9, 133.2,
(ϩ)-3-Hydroxy-2-methylene-4-methylpentanoic
acid
3j
(51%) was obtained as white solids (Found: C, 58.20; H, 8.48;
C7H12O3 requires C, 58.32; H, 8.39%); [α]2D5 ϩ1.6 (c 2.5,
CH3OH); ee 56% (HPLC analysis); νmax(KBr disc)/cmϪ1 2607–
3348, 1678, 1681 and 1630; δH(300 MHz; CDCl3; Me4Si) 7.09
(1 H, br s), 6.44 (1 H, s), 5.90 (1 H, s), 4.13 (1 H, d, J 6.9), 1.98
(2 H, octet, J 6.8), 0.98 (3 H, d, J 6.7) and 0.91 (3 H, d, J 6.8);
δC(75 MHz; CDCl3; Me4Si) 17.5, 19.5, 32.5, 77.4, 128.7, 140.5
and 171.4; m/z (EI) 126 (Mϩ Ϫ 18, 5), 111 (5), 102 (67), 101 (74),
84 (96) and 83 (100). Chiral HPLC analysis of the racemic acid
methyl ester using a Chiralcel OD column with a mixture of
hexane and propan-2-ol (20:1) as the mobile phase at a flow rate
of 0.8 ml minϪ1 gave tϩ = 7.0 min and tϪ = 7.9 min.
Enzymatic hydrolysis of 3-methoxy-2-methylene-3-phenyl-
propiononitrile 5a
3S-(ϩ)-3-Methoxy-2-methylene-3-phenylpropionamide
6a
(47%) was obtained as white solids (Found: C, 69.10; H, 6.87;
O r g . B i o m o l . C h e m . , 2 0 0 3 , 1, 5 3 5 – 5 4 0
539

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N, 7.29. C11H13NO2 requires C, 69.09; H, 6.85; N 7.32%); mp
108–109 ЊC; [α]2D5 ϩ26.67 (c 0.6, CH3OH); ee 53% (HPLC analy-
sis); νmax(KBr disc)/cmϪ1 3397, 3207, 1643 and 1594; δH(300
MHz; DMSO-d6; Me4Si) 7.45 (1 H, s), 7.34–7.25 (5 H, m), 6.99
(1 H, s), 5.84 (1 H, s), 5.50 (1 H, s), 5.12 (1 H, s) and 3.19 (3 H,
s); δC(75 MHz; DMSO-d6; Me4Si) 56.6, 80.8, 118.0, 127.5,
127.8, 128.4, 140.1, 145.0 and 168.4; m/z (EI) 191 (Mϩ, 5%),
190 (13), 176 (23) and 121 (100). Chiral HPLC analysis of the
racemic amide using a Chiralcel OD column with a mixture of
hexane and propan-2-ol (90:10:) as the mobile phase at a flow
rate of 0.8 ml minϪ1 gave tϩ = 17.4 min and tϪ = 14.8 min.
3R-(Ϫ)-3-Methoxy-2-methylene-3-phenylpropionic acid 7a
(43%) was obtained as white solids (Found: C, 68.61; H, 6.22.
C11H12O3 requires C, 68.74; H, 6.29%); mp 53–54 ЊC; [α]2D5
Ϫ107.91 (c 1.39, CH3OH); ee 77% (HPLC analysis); νmax(KBr
disc)/cmϪ1 2750–3500, 1699 and 1630; δH(300 MHz; CDCl3;
Me4Si) 7.35–7.29 (5 H, m), 6.47 (1 H, s), 5.98 (1 H, s), 5.10 (1 H,
s) and 3.35 (3 H, s); δC(75 MHz; CDCl3; Me4Si) 56.9, 80.5,
127.3, 127.4, 127.9, 128.2, 138.8, 140.2 and 170.8; m/z (EI) 192
(Mϩ, 24%), 191 (16), 177 (31), 159 (27), 146 (28) and 121 (100).
Chiral HPLC analysis of the racemic acid using a Chiralcel OJ
column with a mixture of hexane, propan-2-ol and H3PO4
(90:10:0.1) as the mobile phase at a flow rate of 0.8 ml minϪ1
gave tϩ = 24.2 min and tϪ = 15.5 min.
(3 H, d, J 6.7); δC(75 MHz; CDCl3; Me4Si) 17.2, 18.9, 32.4, 57.3,
84.8, 128.5, 138.5 and 171.3; m/z (EI) 157.0869 (C8H14O3
requires 157.0870), 126 (5), 115 (90) and 83 (100). Chiral GC
analysis of the racemic acid using a chiral acidic 750Z column,
10 psi from 110 ЊC to 140 ЊC (2 ЊC minϪ1) gave tϩ = 34.0 min and
tϪ = 32.0 min.
Acknowledgements
We thank the Major Basic Research Development Program
(No. G2000077506), the Ministry of Science and Technology of
China (Grant No. 2002CCA03100), the National Science
Foundation of China and the Chinese Academy of Sciences for
financial Support. M.-X. W also thanks O. Meth-Cohn and
J. Colby for discussion.
References
1 For useful reviews, see: (a) E. Ciganek, Organic Reactions,
ed. L. A. Paquette, John Wiley & Sons, Inc.1997, vol. 51, pp 201–
350; (b) D. Basavaiah, P. D. Rao and R. S. Hyma, Tetrahedron, 1996,
52, 8001; (c) S. E. Drewes and G. H. P. Roos, Tetrahedron, 1988, 44,
4653.
2 For recent examples, see: (a) M. Shi and Y.-S. Feng, J. Org. Chem.,
2001, 66, 406; (b) W.-D. Lee, K.-S. Yang and K. Chen, Chem.
Commun., 2001, 1612; (c) C. Yu, B. Liu and L. Hu, J. Org. Chem.,
2001, 66, 5413.
3 (a) J. Auge, N. Lubin and A. Lubineau, Tetrahedron Lett., 1994, 35,
7947; (b) D. Basavaiah and V. V. L. Gowriswari, Synth. Commun.,
1987, 17, 587.
4 H. Venkatesan and D. C. Liotta, Chemtracts: Org. Chem., 1998, 11,
29.
Enzymatic hydrolysis of 3-methoxy-2-methylenepentanenitrile 5i
( )-3-Methoxy-2-methylenepentanamide
6i
(46%)
was
obtained as white solids mp 32.5–33.5 ЊC; [α]2D5 0 (c 1.2,
CH3OH); ee 7% (GC analysis); νmax(KBr disc)/cmϪ1 3355, 3184,
1671 and 1605; δH(300 MHz; DMSO-d6; Me4Si) 7.49 (1 H, s),
7.10 (1 H, s), 5.84 (1 H, s), 5.41 (1 H, s), 3.96 (1 H, t, J 5.9), 3.17
(3 H, s), 1.62–1.37 (2 H, m) and 0.81 (3 H, t, J 7.4); δC(75 MHz;
DMSO-d6; Me4Si) 9.9, 27.8, 56.4, 80.8, 118.5, 144.2 and 169.1;
m/z (EI) 144.1019 (C7H13NO2 requires 144.1019), 128 (10),
114 (26) and 96 (100). Chiral DC analysis of the racemic amide
using a chiral acidic 750Z column, 10 psi, from 110 ЊC to 140 ЊC
(0.5 ЊC minϪ1) gave t1 = 35.0 min and t2 = 38.0 min.
5 L. J. Brzezinski, S. Rafel and J. W. Leahy, J. Am. Chem. Soc., 1997,
119, 4317.
6 K.-S. Yang and K. Chen, Org. Lett., 2000, 2, 729.
7 (a) K. Burgess and L. D. Jennings, J. Org. Chem., 1990, 55, 1138;
(b) D. Basavaiah and P. D. Rao, Synth. Commun., 1994, 24, 917.
8 (a) T. Sugai, T. Yamazaki, M. Yokoyama and H. Ohta, Biosci.
Biotech. Biochem., 1997, 61, 1419; (b) J. Crosby, J. Moiliet,
J. S. Parratt and N. J. Turner, J. Chem. Soc., Perkin Trans. 1, 1994,
1679.
( )-3-Methoxy-2-methylenepentanoic acid 7i (44%) was
obtained as an oil; [α]2D5 0 (c 0.65, CH3OH); νmax(KBr disc)/cmϪ1
2750–3100, 1698 and 1629; δH(300 MHz; CDCl3; Me4Si) 6.49
(1 H, s), 5.92 (1 H, s), 4.01 (1 H, t, J 5.8), 3.31 (1 H, s), 1.72–1.56
(2 H, m) and 0.93 (3 H, t, J 7.4); δC(75 MHz; CDCl3; Me4Si) 9.4,
28.2, 56.7, 80.3, 127.4, 139.5 and 171.4; m/z (EI) 143.0711
(C7H12O3 requires 143.0714), 129 (6), 115 (85) and 83 (100).
9 For recent examples of enantioselective biotransformation of
nitriles, see: (a) M. A. Wegman, U. Heinemann, A. Stolzs,
F. van Rantwijk and R. A. Sheldon, J. Mol. Catal. Enzymol., 2001,
11, 249; (b) R. Bauer, H. J. Knackmuss and A. Stolzs,
Appl. Microbiol. Biotech., 1998, 49, 89; (c) K. Matoishi, A. Sano,
T. Yamazaki, M. Yokoyama, T. Sugai and H. Ohta, Tetrahedron:
Asymmetry, 1998, 9, 1097; (d ) Z.-L. Wu and Z.-Y. Li, Tetrahedron:
Asymmetry, 2001, 12, 3305.
10 A. J. Balkey, J. Colby, E. Williams and C. O’Reilly, FEMS Microbiol.
Lett., 1995, 129, 57.
11 O. Meth-Cohn and M.-X. Wang, J. Chem. Soc., Perkin Trans. 1,
1997, 1099.
Enzymatic hydrolysis of 3-methoxy-4-methyl-2-
methylenepentanenitrile 5j
12 O. Meth-Cohn and M.-X. Wang, J. Chem. Soc., Perkin Trans. 1,
1997, 3197.
(Ϫ)-3-Methoxy-4-methyl-2-methylenepentanamide 6j (47%)
was obtained as an oil; [α]2D5 Ϫ27.68 (c 0.65, CH3OH); ee 60%
(GC analysis); νmax(KBr disc)/cmϪ1 3419, 3194, 1673, 1624 and
1605; δH(300 MHz; DMSO-d6; Me4Si) 7.43 (1 H, s), 7.03 (1 H,
s), 5.81 (1 H, s), 5.32 (1 H, s), 3.74 (1 H, d, J 5.7), 3.11 (3 H, s),
1.70 (1 H, octet, J 6.6), 0.78 (3 H, d, J 6.3) and 0.76 (3 H, d,
J 6.4); δC(75 MHz; DMSO-d6; Me4Si) 18.1, 19.7, 32.6, 57.3,
85.4, 119.8, 143.8 and 169.9; m/z (EI) 158.1173 (C8H15NO2
requires 158.1175), 142 (12), 125 (16), 114 (52) and 97 (100).
Chiral GC analysis of the corresponding racemic acid methyl
ester using a chiral acidic 750Z column, 14 psi at 80 ЊC gave
tϩ = 10.9 min and tϪ = 11.7 min.
(ϩ)-3-Methoxy-4-methyl-2-methylenepentanoic acid 7j
(44%) was obtained as an oil; [α]2D5 ϩ26.67 (c 0.45, CH3OH);
νmax(KBr disc)/cmϪ1 2750–3100, 1698 and 1627; δH(300 MHz;
CDCl3; Me4Si) 6.54 (1 H, s), 5.87 (1 H, s), 3.82 (1 H, d, J 5.9),
3.30 (3 H, s), 1.89 (1 H, octet, J 6.6), 0.93 (3 H, d, J 6.8) and 0.92
13 (a) M.-X. Wang, G. Lu, G.-J. Ji, Z.-T. Huang, O. Meth-Cohn and
J. Colby, Tetrahedron: Asymmerty, 2000, 11, 1123; (b) M.-X. Wang,
J.-J. Li and J.-S. Li, J. Mol. Catal. Enzymol., 2001, 14, 77;
(c) M.-X. Wang and G.-Q. Feng, Tetrahedron Lett., 2000, 41, 6501;
(d ) M.-X. Wang and S.-J. Lin, Tetrahedron Lett., 2001, 42, 6925;
(e) M.-X. Wang, C.-S. Liu and J.-S. Li, Tetrahedron: Asymmetry,
2001, 12, 3367; ( f ) M.-X. Wang and S.-J. Lin, J. Org. Chem., 2002,
67, 6542; (g) M.-X. Wang and S.-M. Zhao, Tetrahedron: Asymmetry,
2002, 13, 1695; (h) M.-X. Wang and S.-M. Zhao, Tetrahedron Lett.,
2002, 43, 6617; (i) M.-X. Wang and G.-Q. Feng, New J. Chem., 2002,
1575.
14 S. E. Drewes, N. D. Emslie, J. S. Field, A. A. Khan and N. Ramesar,
Tetrahedron: Asymmetry, 1992, 3, 255.
15 J. S. Hill and N. S. Isaacs, J. Chem. Res. Miniprint, 1988, 2641.
16 (a) C.-S. Chen, Y. Fujimoto, G. Girdaukas and C. J. Sih,
J. Am. Chem. Soc., 1982, 104, 7294; (b) Program “Selectivity” by
K. Faber and H. Hoenig, http://www.cis.TUGraz.at/orgc/.
17 A. de Raadt, H. Griengl and H. Weber, Chem. Eur. J., 2001, 7, 27.
O r g . B i o m o l . C h e m . , 2 0 0 3 , 1, 5 3 5 – 5 4 0
540