A study of asymmetric hydrocyanation of heteroaryl carboxaldehydes catalyzed by (R)-oxynitrilase under micro-aqueous conditions

Article abstract of DOI:10.1016/S0957-4166(02)00005-8

A number of new optically active heteroaryl cyanohydrins have been prepared by hydrocyanation under micro-aqueous conditions catalyzed by almond meal (containing (R)-oxynitrilase). Substituent effects on the reaction are discussed. This micro-aqueous meth

Full text of DOI:10.1016/S0957-4166(02)00005-8

TETRAHEDRON:
ASYMMETRY
Pergamon
Tetrahedron: Asymmetry 12 (2001) 3273–3279
A study of asymmetric hydrocyanation of heteroaryl
carboxaldehydes catalyzed by (R)-oxynitrilase under
micro-aqueous conditions
Peiran Chen, Shiqing Han, Guoqiang Lin,* Hao Huang and Zuyi Li
Shanghai Institute of Organic Chemistry, Chinese Academy of Sciences, 354 Fenglin Road, Shanghai 200032, China
Received 20 November 2001; accepted 21 December 2001
Abstract—A number of new optically active heteroaryl cyanohydrins have been prepared by hydrocyanation under micro-aqueous
conditions catalyzed by almond meal (containing (R)-oxynitrilase). Substituent effects on the reaction are discussed. This
micro-aqueous method provides an efficient, convenient and economical approach to optically active cyanohydrins. © 2002
Published by Elsevier Science Ltd.
1
. Introduction
and the aldehyde carbonyl group that causes the inhibi-
tion of the hydrocyanation reaction. Elimination of the
hydrogen bond by protecting the NH group might
therefore provide a way to improve the situation. In
addition, we were also interested in undertaking an
investigation into the effect of ring substituents on the
hydrocyanation reaction. In many cases, almond meal
has been proven to be as efficient as the purified
enzyme and as convenient as the immobilized enzyme
Optically active cyanohydrins are useful intermediates
in the synthesis of a variety of natural and non-natural
compounds of biological interest because the stereo-
genic carbon atom in the molecule bears two function-
alities,
which
can
readily
undergo
further
transformation. For example, the preparation of
homochiral amino alcohols starting from optically
active cyanohydrins in most cases is easier and more
efficient. Among cyanohydrins, heteroaryl cyanohy-
drins are of special importance, which constitute the
structural moiety of many biologically active
3
4
by Brussee and by ourselves. It is known that reaction
in an organic solvent can effectively depress the non-
stereoselective addition of HCN to the carbonyl group
via chemical pathway and minimize the reversible equi-
librium between HCN addition and cyanohydrin
decomposition. As such, we carried out the hydrocya-
nation of a variety of substituted heteroaryl carboxalde-
hydes using almond meal as the catalyst under
1
molecules. Routes to optically active cyanohydrins can
be categorized into non-enzymatic and enzymatic
approaches. In the former there are the chiral complex-
controlled methods and the cyclic dipeptide-catalyzed
method, while in the latter, transformations by lipases
4
2
‘micro-aqueous conditions’. Herein we wish to report
and oxynitrilases have been reported. However, only a
our results.
few chiral heteroaryl cyanohydrins containing O- or
S-atoms in the heterocyclic ring have been successfully
synthesized by the isolated or recombinant (R)- or
(
S)-oxynitrilases, whilst the hydrocyanations of N-con-
2. Results and discussion
taining heteroaryl carboxaldehydes have been reported
to be unsuccessful.
2
2.1. ‘Micro-aqueous conditions’ for the asymmetric
hydrocyanation of heteroaryl carboxaldehydes
In analyzing the structural feature of some NH-con-
taining heteroaryl carboxaldehydes, we hypothesised
that it might be the hydrogen bond between the N–H
In efforts to optimise the reaction conditions with
almond preparations as the catalyst, we found that
dried almond powder gave no hydrocyanation product,
even when the reaction was carried out in water-satu-
rated iso-propyl ether (IPE) (which was determined to
*
Corresponding author. Tel.: +86-21-64163300; fax: +86-21-
4166263; e-mail: lingq@pub.sioc.ac.cn
6
0
957-4166/01/$ - see front matter © 2002 Published by Elsevier Science Ltd.
PII: S0957-4166(02)00005-8

3
274
P. Chen et al. / Tetrahedron: Asymmetry 12 (2001) 3273–3279
contain about 0.3% water). Therefore, almond kernels
were firstly saturated with water then pulverized, which
resulted in a water content of about 9% in the tissue of
the almond powder. This water content satisfies the
need of the enzyme for essential water to exhibit its full
activity, and the organic medium used for the reaction
has so little water content that it can effectively prevent
the resultant cyanohydrins from decomposition into the
starting aldehyde and racemization, additionally the
reactions are carried out at ambient temperature. In
order to compare the stability of the resulting cyanohy-
drin in aqueous buffer and in iso-propyl ether, (S)-2-(2-
furanyl)-2-hydroxynitrile was dissolved in citrate buffer
the former case and with an e.e. value of 99% and yield
7a
of 70% in the latter case. The results obtained by
performing the reaction under micro-aqueous condi-
tions with these two substrates are similar to those
reported previously (Table 1, entry a, b). Methyl substi-
tution at the 5-position leads to a significant decrease in
the yield, which may be attributed to steric hindrance
resulting in poor fit between the substrate and the
enzyme. 2-Methyl-furanyl-3-carboxaldehyde (entry c)
gave moderate yield and low e.e. The reaction was
totally inhibited when the furan ring bore a hydroxy-
methyl or acetoxymethyl group at the 5-position. Intro-
duction of a nitro group caused the aldehyde to be so
reactive that a tar formed without any desired product
detected.
(
pH 5.5) and in isopropyl ether, respectively. The for-
mation of the 2-furanylcarboxaldehyde by decomposi-
tion and racemization of the cyanohydrin was
determined for the two conditions. It was found that
the cyanohydrin underwent rapid decomposition and
racemization in aqueous solution, whereas it was fairly
stable in iso-propyl ether. Therefore, micro-aqueous
2.3. Thien-2-yl carboxaldehydes
Thien-2-yl cyanohydrin was obtained under our condi-
tions in similar yield and stereoselectivity to those
4
5
conditions can provide an environment for the hydro-
reported by Effenberger et al. (Table 2, entry a).
cyanation reaction which minimizes the decomposition
and racemization of the formed cyanohydrins.
Introduction of a methyl substituent at the 3-position
of the thienyl ring also resulted in a significant decrease
both in the yield and enantiomeric excess as in the case
of 5-methylfuran-2-yl cyanohydrin mentioned above
(entry c). Interestingly, bromo substitution at the 5-
position maintained the yield of the cyanohydrin at the
same level as the non-substituted substrate and did not
decrease the product e.e. as much as in the case of
methyl substitution (entry b). This may be a result of a
balance between the activation effect on the carbonyl
group and steric hindrance from the bromo moiety.
The general hydrocyanation reaction is shown in the
following scheme.
2.2. Furanyl carboxaldehydes
2.4. Pyrrolylcarboxaldehydes and
indolylcarboxaldehydes
Transformation of furan-2-yl and 5-methylfuran-2-yl
carboxaldehyde to the corresponding cyanohydrins has
been accomplished under the catalysis of (R)-oxynitri-
lase isolated from almond nuts (Prunus amygdalus)
The use of N-containing five-membered heteroaryl car-
boxaldehydes as the substrate of enzymatic hydrocya-
nation has so far not been extensively studied. As
5
6a
8
with an e.e. value of 99% and yield of 96 or 88% in
reported by Griengl et al., pyrrolyl- and indolyl-car-
Table 1. Hydrocyanation of some furanyl carboxaldehydes under micro-aqueous conditions

P. Chen et al. / Tetrahedron: Asymmetry 12 (2001) 3273–3279
3275
Table 2. Hydrocyanation of some thien-2-yl carboxaldehydes under micro-aqueous conditions
boxaldehydes gave no product in the hydrocyanationre-
action catalyzed either by isolated (R)-oxynitrilase
2.5. Pyridinyl-carboxaldehydes
(
from almond, Prunus amygdalus) or by (S)-oxynitri-
All pyridinyl 2-, 3- and 4-carboxaldehydes have been
reported to give no hydrocyanation product under the
lase (from rubber tree, Hevea brasiliensis). We assumed
that the intra- or intermolecular hydrogen bonds
between the hydrogen atom of the ring nitrogen and the
oxygen atom of the carbonyl group in the substrate
molecules might deactivate the carbonyl group. There-
fore, a series of N-blocked substrates was tested for
hydrocyanation under our conditions. The results
appear to support our assumption. Most of the N-
blocked substrates gave the corresponding cyanohy-
drins with varying yields and enantiomeric excesses.
Although many substrates did not give products with
preparative significance, the results in some cases are
promising and practical. N-Ts and N-Boc protected
pyrrolylcarboxaldehydes (entry a and b) gave no good
results (both yield and e.e.), probably due to the bulk of
the protecting groups, which may interfere with the
interaction between the substrate and the enzyme.
Pyrrolylcarboxaldehydes with N-blocked by a methyl
8b
catalysis of (S)-oxynitrilase isolated from rubber tree
(Hevea brasiliensis). In the case of the enzyme isolated
from almond (Prunus amygdalus), pyridinyl 3-carbox-
aldehyde was reported to give (R)-pyridin-3-yl
6a
cyanohydrin in 89% yield and 14% e.e., and 97% yield
6b
and 82% e.e., respectively, whereas the transformation
of other pyridinyl carboxaldehydes has not been
reported.
Under our reaction conditions, the results of the hydro-
cyanation of pyridinyl-carboxaldehydes varied dramati-
cally with the position of the aldehyde group on the
pyridine ring (Table 4). Pyridin-2-yl carboxaldehyde
(entry a) gave the corresponding cyanohydrin in moder-
ate yields and 0 e.e., pyridin-3-yl carboxaldehyde (entry
d) produced its cyanohydrin in 99.5% yield and 50%
e.e. and pyridin-4-yl carboxaldehyde formed a tar. Sub-
stitution on the pyridine ring also gave varied results.
Again, bromo substitution at a position ortho to the
hetero-atom improved both the yield and e.e. (entry c),
whereas methyl substitution at the same position pro-
vided no good effect (entry b).
(
(
Table 3, entry d) or a methoxymethyl group (MOM)
entry c) afforded the corresponding cyanohydrins in
low yields and with modest enantioselectivities. Substi-
tution at the 5-position with an acetyl (entry e) or a
cyano group (entry f) significantly improved the yields
with moderate enantiomeric excesses. Nitro- or chloro-
substituents at position 5 gave adverse effects, resulting
in the formation of a tar. A methoxy group on the
2.6. Heteroaryl-carboxaldehydes containing two hetero-
atoms in the ring
5
-position afforded no reaction with recovery of the
starting material. In the case of the indolyl series,
compared to the parent compound, blocking the nitro-
gen atom by Boc promoted the reaction (entry g),
although the result was still not satisfactory. This may
be due to the bulky backbone of the aryl ring itself,
which results in poor fit with the enzyme. Protonation
of the nitrogen atom under the acidic medium may be
the other reason which results in an adverse effect on
the outcome of the reaction.
The enzymatic hydrocyanation of heteroaryl carbox-
aldehydes containing two heteroatoms in the ring has
so far not been reported. 1-N-Methyl-imidazol-2-yl car-
boxaldehyde gave the corresponding cynaohydrin in
high yield and low e.e. (Table 5, entry a), but no
hydrocyanation reaction occurred with both unpro-
tected imidazolyl and 1-N-MOM-imidazol-2-yl carbox-
aldehydes. Fortunately, thiazol-2-yl cyanohydrin was
obtained from the carboxaldehyde in good yield and

3
276
P. Chen et al. / Tetrahedron: Asymmetry 12 (2001) 3273–3279
moderate enantiomeric excess (Table 5, entry b), which
we believe will find appreciable applications in the
synthesis of biologically interesting compounds.
aldehyde so much that a black tar was formed without
any desired products detected; heteroaryl carboxalde-
hydes substituted with moderate electron-withdrawing
groups such as halogen and cyano groups usually gave
modest yields and e.e.s.
3
. Conclusions
It is believed that these new heteroaryl cyanohydrins
will find application in the synthesis of biologically
interesting molecules.
A number of new optically active heteroaryl cyanohy-
drins have been prepared from heteroaryl carboxalde-
hydes under the catalysis of almond meal using
4
micro-aqueous conditions. The effect of substituents of
the heteroaryl ring on the reaction has also been exam-
ined. Introduction of a substituent generally gave
results in both yield and e.e., which were no better than
the corresponding parent compounds. It seems that
electron-donating groups such as methyl, hydroxy-
methyl, and methoxy groups reduce the reactivity of
the aldehydes preventing the hydrocyanation reaction
from occurring; the presence of strong electron-with-
drawing groups such as a nitro group activates the
4. Experimental
4.1. Materials and methods
All of the heteroaryl carboxaldehydes used were pur-
chased from Acros Organics. N-Protection with Boc,
methoxymethyl, methyl, and tosyl groups for pyrrolyl-,
indolyl- and imidazolyl-carboxaldehydes was performed
by known methods.
Table 3. Hydrocyanation of some pyrrolyl- and indolylcarboxaldehydes under micro-aqueous conditions

P. Chen et al. / Tetrahedron: Asymmetry 12 (2001) 3273–3279
3277
Table 4. Hydrocyanation of some pyridinyl-carboxaldehydes under micro-aqueous conditions
Table 5. Hydrocyanation of some heteroaryl-carboxaldehydes containing two heteroatoms in the ring under micro-aqueous
conditions
1
Melting points are uncorrected. H NMR spectra were
recorded on a Bruker AM 300 (300 MHz) with TMS as
an internal reference; EI mass spectra were measured
on an HP 5989A; high resolution mass spectra (FAB)
were measured on a Finnigan MAT 8430; infrared
spectra were acquired on a Perkin Elmer 983 or Digibal
FTIR; optical rotations were determined on a Perkin–
Elmer 241MC. Enantiomeric excess values were
obtained by first either acetylating or benzoylating the
cyanohydrins by known methods, then subjecting the
acylated products to HPLC analysis on Chiralpak
columns. The e.e. determinations and elemental analy-
ses on a Heraeus Rapid-CHNO elemental analyzer
were performed by the Analytical Department of this
Institute. Water contents in the crude enzyme and in
iso-propyl ether used in the enzymatic reaction was
determined on a Mettler DL35 Karl–Fischer titrator.
The almond kernals used in this study were obtained
from fresh fruits of almond produced in Lishi County,
Shanxi Province.
4.2. Preparation of racemic cyanohydrins
A mixture of aldehyde (1 mmol), 10% aqueous
NaHSO (1.5 mL) and ethyl ether was stirred at 0°C for
3
1 h. To the stirred mixture 20% aqueous KCN (0.4 mL)
was added. The resultant mixture was stirred at 0–30°C
for 2–24 h. The aqueous phase was separated and
extracted with ethyl ether (2×10 mL). The combined
organic phase was washed with water (10 mL) and
dried over Na SO . Flash chromatography on silica gel
2
4
(eluent: ethyl acetate/petroleum ether) gave the corre-
sponding racemic cyanohydrins, which were used as
references in e.e. value determination.

3
278
P. Chen et al. / Tetrahedron: Asymmetry 12 (2001) 3273–3279
+
+
4
.3. Crude enzyme preparation
100), 136 (20), 126 (M −HCN, 88), 125 (M −HCN−H,
00), 97 (36), 53 (18), 45 (20), 44 (30); HRMS (FAB):
C H NOS. Found: 153.0213, calcd: 153.0248.
1
Almond kernels were swollen by soaking in distilled
water for 2 h, peeled, air-dried and then pulverized in
cooled ethyl acetate with a homogenizer. The resultant
powder was filtered and de-fatted by three washes with
ethyl acetate, filtered and stored in a refrigerator.
7
7
4.4.7. (R)-(+)-2-Hydroxy-2-(2-(N-methoxymethyl)pyrro-
2
1
lyl)acetonitrile 3c. Clear oil; yield: 33%; [h] +104.9
D
1
(c=0.667, CHCl ); e.e. 81%; H NMR (CDCl ): l, 3.30
3
3
(
s, 3H, CH ), 3.92 (br, s, 1H, OH), 5.08–5.68 (AB, 2H,
3
4.4. General procedure for enzymatic hydrocyanation
J=10.9 Hz, CH ), 5.56 (s, 1H, CH), 6.13 (dd, 1H,
J =3.5 Hz, J =3.0 Hz, Pyrr-H), 6.47 (dd, 1H, J =3.6
2
1
2
1
A mixture of aldehyde (1.25 mmol), almond meal (0.5
g), and 2 M HCN in isopropyl ether (5 mL) was stirred
at 4–30°C for 16–100 h. Flash chromatography on
silica gel (eluent: ethyl acetate/petroleum ether) pro-
vided the corresponding cyanohydrins.
Hz, J =1.7 Hz, Pyrr-H), 6.83 (dd, 1H, J =2.9 Hz,
2 1
13
J2=1.7 Hz, Pyrr-H); C NMR: l, 126.38 (t-C-Pyrr),
125.59 (C-Pyrr), 118.01 (CN), 113.18 (C-Pyrr), 108.01
(C-Pyrr), 78.63 (NCH O), 56.55 (CHOH), 55.995
2
−
1
(OCH ); IR (cm ): 3402, 3117, 2934, 2851, 2247, 1486,
3
1
464, 1444, 1400, 1277, 1097, 1025, 732; MS: m/z (rel.
+
4
.4.1. (S)-(+)-2-Hydroxy-2-(2-furyl)acetonitrile 1a. Clear
intensity, %): 166 (M , 5), 149 (4), 139 (9), 124 (31), 108
(17), 94 (7), 80 (10), 71 (9), 57 (13), 45 (100), 41 (12);
HRMS (FAB): C H N O . Found: 166.0732, calcd:
2
1
9
oil; yield: 100%; [h] +50.0 (c=1.60, CHCl ), (lit
D
3
1
value: +50.3); e.e. 99%; H NMR (CDCl ): l, 3.17 (br,
s, 1H, OH), 5.55 (s, 1H, CH), 6.43 (dd, 1H, J =1.9 Hz,
3
8
10
2
2
166.0742.
1
J2=3 Hz, Ar-H), 6.61 (m, 1H, Ar-H), 7.49 (m, 1H,
Ar-H).
4
.4.8. (R)-(+)-2-Hydroxy-2-(2-(N-methyl)pyrrolyl)acet-
21
onitrile 3d. Clear oil; yield: 17%; [h] +35.7 (c=1.2,
D
4
1
.4.2. (S)-(+)-2-Hydroxy-2-(5-methyl-2-furyl)acetonitrile
21
1
CHCl ); e.e. 40.1%; H NMR (CDCl ): l, 2.90 (br, s,
1H, OH), 5.50 (s, 1H, Pyrr-H), 6.38 (m, 1H, Pyrr-H),
3
3
b. Clear oil; yield: 60%; [h] +61.0 (c=1.60, CHCl3);
D
1
e.e. 97.2%; H NMR (CDCl ): l, 2.5 (s, 3H, CH ), 3.0
3
3
−
1
6
2
.67 (m, 1H, Pyrr-H); IR (cm ): 3414 (w), 3114, 2953,
248 (CN), 1644, 1543, 1494, 1417, 1300, 1024, 729;
(
s, 1H, OH), 5.5 (s, 1H, CH), 6.0–7.2 (m, 2H, Ar-H).
+
+
MS: m/z (rel. intensity, %): 137 (M +1, 5), 136 (M ,
4
.4.3. (R)-(+)-2-Benzoyloxy-2-(2-methyl-3-furanyl)acet-
+
+
+
2
1
D
56), 121 (M −CH , 2), 120 (M −1−CH , 9), 119 (M +
3 3
+ +
onitrile 1c. Clear oil; yield 78%; [h] +8.2 (c=6.5,
1
1−H O, 100), 109 (M −HCN, 49), 108 (M −1−HCN,
2
CHCl ); e.e. 24.3%; H NMR (CDCl ): l, 2.6 (s, 3H,
3
3
4
4), 91 (14), 80 (24), 65 (16), 57 (24), 53 (32), 41 (23);
CH ), 5.5 (s, 1H, CH), 6.5–7.5 (m, 7H, Ar-H); IR
3
−
1
HRMS (FAB): C H N O. Found: 136.0613, calcd:
7
8
2
(
1
cm ): 3401, 2806, 2511, 1790, 1726, 1601, 1591, 1492,
452, 1280, 1011, 996, 930, 869. MS: m/z (rel. intensity,
1
36.0637.
+
+
+
%
): 137 (M , 94), 120 (M −OH, 86), 119 (M −H O,
2
64), 110 (94), 109 (100), 81 (44), 53 (78), 43 (98);
4
.4.9. (R)-(+)-2-Hydroxy-2-(2-(5-acetyl-N-methyl)pyr-
HRMS (FAB): C H NO . Found: 241.0799, calcd:
1
4
11
3
rolyl)acetonitrile 3e. White solid, mp=96–97°C; yield:
241.0740.
21
1
9
9%; [h]D +38.8 (c=0.80, EtOH); e.e. 34.1%; H NMR
(
acetone-d ): l, 2.40 (s, 3H, CH CO), 3.30 (s, 1H, OH),
6
3
4
.4.4. (S)-(+)-2-Hydroxy-2-(2-thienyl)acetonitrile 2a.
3
.96 (s, 3H, N-CH ), 5.93 (s, 1H, CH), 6.37 (d, 1H,
3
2
1
Clear oil; yield: 70%; [h] +61.6 (c=1.60, CHCl ); e.e.
D
3
J=4 Hz, Pyrr-H), 7.03 (d, 1H, J=4 Hz, Pyrr-H); IR
1
99%; H NMR (CDCl ): l, 3.0 (s, 1H, OH), 5.8 (s, 1H,
−1
3
(
1
cm ): 3337, 3200 (w), 3127, 2966, 2918, 2846, 2246,
645, 1625, 1531, 1492, 1458, 1385, 1250, 1027, 768;
CH), 6.9–7.4 (m, 3H, Ar-H).
+
+
MS: m/z (rel. intensity, %): 179 (M +1, 5), 178 (M ,
4
.4.5. (S)-(+)-2-Hydroxy-2-(5-bromo-2-thienyl)acet-
+
+
1
6), 163 (M −CH , 15), 151 (M −HCN, 100), 136
3
2
1
onitrile 2b. Clear oil; yield: 72%; [h] +19.7 (c=1.60,
+
D
(
M −CH −HCN, 78), 123 (14), 108 (19), 80 (22), 53
23), 43 (19); elemental analysis: C H N O . Found: C,
3
1
CHCl ); e.e. 86%; H NMR (CDCl ): l, 3.0 (s, 1H,
3
3
(
9
10
2
2
OH), 5.7 (s, 1H, CH), 7.3–7.4 (m, 2H, Ar-H); IR
6
1
0.5; H, 5.57; N, 15.78, calcd: C, 60.55; H, 5.66; N,
5.75%.
−
1
(
cm ): 3386, 3109, 2922, 1526, 1401, 1339, 1301, 1253,
1
5
187, 1145, 1125, 1062, 1030, 903, 841, 820, 750, 628,
+
78; MS: m/z (rel. intensity, %): 219 (M +H, 53) 217
+
+
+
(
1
M −H, 54), 192 (M −CN, 67), 191 (M −HCN, 100),
4.4.10. (R)-(+)-2-Hydroxy-2-(3-(5-cyano-N-methyl)pyr-
rolyl)acetonitrile 3f. White solid, mp=104–105°C; yield:
84%; [h]D +24.7 (c=0.75, EtOH); e.e. 66.4%; H NMR
(acetone-d ): l, 3.30 (s, 1H, OH), 3.82 (s, 3H, N-CH ),
+
90 (M −HCN−H, 86), 189 (91), 138 (67), 82 (45);
HRMS (FAB): C H BrNOS. Found: 190.9183, calcd:
21
1
6
4
190.9166.
6
3
5
.62 (s, 1H, CH), 6.96 (d, 1H, J=1.8 Hz, Pyrr-H), 7.26
−1
4
.4.6. (S)-(+)-2-Hydroxy-2-(3-methyl-2-thienyl)acet-
(d, 1H, J=1.8 Hz, Pyrr-H); IR (cm ): 3406, 3125,
3093, 2954, 2881, 2225, 1561, 1484, 1414, 1398, 1214,
1135, 1052, 845, 600; MS: m/z (rel. intensity, %): 162
21
onitrile 2c. Clear oil; yield: 48%; [h] +24.5 (c=5.0,
D
1
CHCl ); e.e. 65%; H NMR (CDCl ): l, 2.5 (s, 3H,
CH ), 3.0 (s, 1H, OH), 5.8 (s, 1H, CH), 6.9–7.4 (m, 3H,
Ar-H); IR (cm ): 3404, 3110, 2926, 2864, 2250, 1639,
3
3
+
+
+
+
(M +1, 8), 161 (M , 34), 144 (M −OH, 32), 135 (M −
+ +
3
−
1
CN, 52), 134 (M −HCN, 65), 134 (M −H−HCN, 100),
117 (3), 105 (14), 78 (9), 64 (9); HRMS (FAB):
C H N O. Found: 161.0896, calcd: 161.0859.
1
7
554, 1428, 1387, 1257, 1179, 1015, 942, 920, 846, 836,
28, 680, 589; MS: m/z (rel. intensity, %): 153 (M ,
+
8
7
3

P. Chen et al. / Tetrahedron: Asymmetry 12 (2001) 3273–3279
3279
4
.4.11. (R)-(+)-2-Hydroxy-2-(6-bromo-2-pyridinyl)acet-
Basic Research Development Program (Grant No.
2000077506), and The National Natural Science Foun-
dation of China (Grant No. 29972050) for financial
support.
2
1
onitrile 4c. Clear oil; yield: 92%; [h] +22.4 (c=1.60,
D
1
CHCl ); e.e. 65%; H NMR (CDCl ): l, 4.4 (s, 1H,
OH), 5.5 (s, 1H, CH), 7.3–7.4 (m, 3H, Ar-H); IR
3
3
−
1
(
cm ): 3105, 2927, 2682, 1589, 1562, 1456, 1435, 1306,
1
5
1
262, 1245, 1163, 1137, 1075, 1001, 931, 792, 745, 649,
96; MS: m/z (rel. intensity, %): 212 (M , 19), 159 (98),
+
References
58 (48), 157 (100), 156 (34), 78 (42), 77 (20), 76 (29), 51
+
(
2
24); HRMS (FAB): C H BrN O (M −H): found:
1. For examples, see: (a) Asselin, A. A.; Humber, L. G.;
Crosilla, D.; Oshiro, G.; Wojdan, A.; Grimes, D.;
Heaslip, R. J.; Rimele, T. J.; Shaw, C. C. J. Med. Chem.
1986, 29, 1009; (b) Naylor, E. M.; Colandrea, V. J.;
Candelore, M. R. Bioorg. Med. Chem. Lett. 1998, 8,
3087.
2. For more recent reviews about the preparation of
cyanohydrins catalyzed by oxynitrilases, see: (a) Effen-
berger, F.; F o¨ ster, S.; Wajant, H. Curr. Opin. Biotechnol.
2001, 532 and references cited therein; (b) Gr o¨ ger, H.
Adv. Synth. Catal. 2001, 343, 547; (c) Gregory, R. J. H.
Chem. Rev. 99, 1999, 3649 and references cited therein.
3. Brussee, J.; Loos, W. T.; Kruse, C. G.; van der Gen, A.
Tetrahedron 1990, 46, 979.
7
5
2
11.9561, calcd: 211.9585.
4
.4.12. (R)-(+)-2-Hydroxy-2-(3-pyridinyl)acetonitrile 4d.
2
1
White crystal, mp=85–86°C; yield 99.5%; [h] +21.4
D
1
(
(
c=0.95, EtOH); e.e. 50%; H NMR (CDCl ): l, 5.55
br, s, 1H, OH), 5.65 (s, 1H, CH); 7.45 (dd, 1H, J =8
3
1
Hz, J =1.6 Hz, Py-H), 7.98 (dd, 1H, J =8 Hz, J =1.6
2
1
2
Hz, Py-H), 8.56 (d, 1H, J=4.8 Hz, Py-H), 8.61 (s, 1H,
Py-H).
4
.4.13. (S)-(−)-2-Hydroxy-2-(2-N-methylimidazolyl)-
acetonitrile 5a. Colorless crystal, mp=124°C (decomp.);
2
1
1
yield: 94%; [h]D −2 (c=0.30, MeOH); e.e. 5%;
H
NMR (CD OD): l, 4.0 (s, 4H, CH , OH), 6.03 (s, 1H,
4. (a) Han, S.; Lin, G.; Li, Z. Tetrahedron: Asymmetry
1998, 9, 1835; (b) Han, S.; Lin, G.; Li, Z. Tetrahedron
1999, 55, 3531; (c) Han, S.; Chen, P.; Lin, G.; Li, Z.
Tetrahedron: Asymmetry 2001, 12, 843.
3
3
CH), 7.13 (d, 1H, J=1.0 Hz, Im-H), 7.35 (d, 1H,
J=1.0 Hz, Im-H); IR (cm ): 2500–3300 (w), 3148,
3
1
−
1
062, 2817, 2693, 2065, 1681, 1666, 1504, 1468, 1427,
392, 1280, 1035, 925, 748, 719; MS: m/z (rel. intensity,
5. Effenberger, F.; Eichhorn, J. Tetrahedron: Asymmetry
+
+
+
%
): 138 (M +1, 11), 137 (M , 33), 120 (M −OH, 35),
1997, 8, 469.
+ +
1
(
11 (M −CN, 36), 110 (M −HCN, 83), 97 (11), 82
100), 81 (72), 54 (61), 42 (66); elemental analysis:
C H N O. Found: C, 52.23; H, 5.12; N, 30.72, calcd: C,
6. (a) Effenberger, F.; Ziegler, T.; Forster, S. Angew.
Chem., Int. Ed. Engl. 1987, 26, 458; (b) Effenberger, F.
Angew. Chem., Int. Ed. Engl. 1994, 33, 1555; (c) Effen-
berger, F. Enantiomer 1996, 1, 359; (d) Loos, W. T.;
Geluk, H. W.; Ruijken, M. M. A.; Kruse, C. G.; Brus-
see, J.; van der Gen, A. Biocatalysis and Biotransforma-
tion 1995, 12, 255.
7. (a) Zandbergen, P.; van der Linden, J.; Brussee, J.; van
der Gen, A. Synth. Commun. 1991, 21, 1387; (b) Huuh-
tanen, T. T.; Kanerva, L. T. Tetrahedron: Asymmetry
1992, 3, 1223; (c) Kiljunen, E.; Karneva, L. T. Tetra-
hedron: Asymmetry 1996, 7, 1105; (d) Kiljunen, E.;
Karneva, L. T. Tetrahedron: Asymmetry 1997, 8, 1225;
(e) Kiljunen, E.; Karneva, L. T. Tetrahedron: Asymmetry
1997, 8, 1551.
6
7
3
52.55; H, 5.15; N, 30.64%.
4
.4.14. (S)-(+)-2-Hydroxy-2-(2-thiazolyl)acetonitrile 5b.
2
1
Light yellow crystal, mp=133–134°C; yield 97%; [h]
D
1
+
13 (c=0.4, EtOH); e.e. 67%; H NMR (CD OD): l,
3
6
.17 (s, 1H, CH), 7.89 (AB, 1H, Ar-H, J=3.3 Hz), 8.03
−1
(AB, 1H, Ar-H, J=3.3 Hz); IR (cm ): 3125 (w), 2843,
2
725, 1508, 1454, 1408, 1187, 1123, 1046, 909, 753; MS:
+
+
m/z (rel. intensity, %): 142 (M +2, 4), 141 (M +1, 15),
+
+
+
1
40 (M , 30), 123 (M −OH, 13), 114 (M −CN, 20), 110
+
(
M −HCN, 26), 95 (8), 86 (68), 85 (51), 58 (100), 45
21); elemental analysis: C H N OS. Found: C, 42.87;
(
5
4
2
H, 2.78; N, 20.03, calcd: C, 42.85; H, 2.88; N, 19.98%.
8. (a) Schmidt, M.; Griengl, H. In Oxynitrilases: From
Cyanogenesis to Asymmetric Synthesis; Fessner, W.-D.,
Ed. Topics in Current Chemistry; Springer-Verlag:
Berlin, 1999; Vol. 200, pp. 193–226; (b) Schmidt, M.;
Herve, S.; Klempier, N.; Griengl, H. Tetrahedron 1996,
Acknowledgements
52, 7833.
The authors are grateful to The Chinese Academy of
Sciences (Grant No. KJ951A150605), The Major State
9. Ziegler, T.; H o¨ rsch, B.; Effenberger, F. Synthesis 1990,
7, 575.