Nitrile biotransformations for the synthesis of enantiomerically enriched β2-, and β3-hydroxy and -alkoxy acids and amides, a dramatic O-substituent effect of the substrates on enantioselectivity

Article abstract of DOI:10.1016/j.tetasy.2008.01.017

Rhodococcus erythropolis AJ270, a nitrile hydratase/amidase-containing microbial whole cell catalyst, is able to catalyze the hydrolysis of a number of β-hydroxy and β-alkoxy nitriles under very mild conditions. Both the efficiency and enantioselectivity of the biocatalysis, however, were strongly dependent upon the structures of both nitrile and amide substrates. When biotransformations of racemic 3-hydroxy-3-phenylpropionitrile and 2-hydroxymethyl-3-phenylpropionitrile gave low enantioselectivity, their O-methylated isomers underwent highly efficient and enantioselective biocatalytic reactions to afford highly enantioenriched β²- and β³-hydroxy amide and acid derivatives in excellent yield. The study has provided an example of simple and very convenient substrate engineering method to increase the enantioselectivity of the biocatalytic reaction.

Full text of DOI:10.1016/j.tetasy.2008.01.017

Available online at www.sciencedirect.com
Tetrahedron: Asymmetry 19 (2008) 322–329
Nitrile biotransformations for the synthesis of enantiomerically
enriched b2-, and b3-hydroxy and -alkoxy acids and amides, a
dramatic O-substituent effect of the substrates on enantioselectivity
Da-You Ma, De-Xian Wang, Jie Pan, Zhi-Tang Huang and Mei-Xiang Wang*
Beijing National Laboratory for Molecular Sciences, Laboratory of Chemical Biology, Institute of Chemistry,
Chinese Academy of Sciences, Beijing 100080, China
Received 23 November 2007; accepted 8 January 2008
Abstract—Rhodococcus erythropolis AJ270, a nitrile hydratase/amidase-containing microbial whole cell catalyst, is able to catalyze the
hydrolysis of a number of b-hydroxy and b-alkoxy nitriles under very mild conditions. Both the efficiency and enantioselectivity of the
biocatalysis, however, were strongly dependent upon the structures of both nitrile and amide substrates. When biotransformations of
racemic 3-hydroxy-3-phenylpropionitrile and 2-hydroxymethyl-3-phenylpropionitrile gave low enantioselectivity, their O-methylated iso-
mers underwent highly efficient and enantioselective biocatalytic reactions to afford highly enantioenriched b2- and b3-hydroxy amide
and acid derivatives in excellent yield. The study has provided an example of simple and very convenient substrate engineering method
to increase the enantioselectivity of the biocatalytic reaction.
Ó 2008 Elsevier Ltd. All rights reserved.
1. Introduction
tion of a nitrile followed by the amide hydrolysis catalyzed
by the amidase,10 are an effective and environmentally
benign method for the production of carboxylic acids and
their amide derivatives.11 Studies have demonstrated that
the biotransformations of nitriles complement the existing
asymmetric chemical and enzymatic methods for the syn-
thesis of chiral carboxylic acids and their derivatives.12,13
The distinct features of enzymatic transformations of
nitriles are the formation of enantiopure carboxylic acids
and the straightforward generation of enantiopure amides,
which are valuable organonitrogen compounds in synthetic
chemistry. Recently, we have shown that Rhodococcus ery-
thropolis AJ270,14 a nitrile hydratase/amidase-containing
whole cell catalyst, is able to efficiently and enantioselec-
tively transform a number of racemic nitriles including a-
alkylated and functionalized nitriles,15 a-aminonitriles,16
cyclopropanecarbonitriles,17 oxiranecarbonitriles,18 and
aziridinecarbonitriles19 into chiral carboxylic acids and
amide derivatives. Racemic nitriles bearing a b-stereogenic
center were also biocatalytically transformed into the
corresponding enantiopure acids and amides, provided
the substrates were designed carefully.20 For example, R.
erythropolis AJ270-catalyzed hydrolysis of racemic b-benz-
yloxy alkanenitriles led to the formation of highly enantio-
pure b-benzyloxy alkanoic acids and amides whereas the
biotransformations of racemic b-hydroxy alkanenitriles
Optically active b3- and b2-hydroxy carboxylic acids, b-hy-
droxy carboxylic acids that contain, respectively, a substitu-
ent at the 3- and 2-position, and their derivatives are key
intermediates in the synthesis of natural products and bio-
logically important compounds.1 3-Hydroxy-3-phenylpro-
pionic acid and its amide derivatives, for example, have
been used as the precursors to chiral drugs such as tomoxe-
tine and fluorine and nisoxetine.2 Much effort has been
devoted to the synthesis of chiral b-hydroxy carboxylic acids
and their derivatives. The synthetic methods documented so
far include catalytic asymmetric hydrogenation,1a,3 reduc-
tion,4 Mukaiyama-aldol reaction,5 and Reformatsky
reaction.6 Biocatalytic reduction of b-ketoesters,7 enzyme-
catalyzed kinetic resolution of secondary alcohols,8 and
microbial deracemization of racemic ethyl 3-aryl-3-hydroxy
propionic acid ester9 have also been reported.
Biotransformations of nitriles, either through direct con-
version from a nitrile to a carboxylic acid catalyzed by a
nitrilase or through the nitrile hydratase-catalyzed hydra-
*
Corresponding author. Tel.: +86 10 62565610; fax: +86 10 62564723;
e-mail: mxwang@iccas.ac.cn
0957-4166/$ - see front matter Ó 2008 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tetasy.2008.01.017

D.-Y. Ma et al. / Tetrahedron: Asymmetry 19 (2008) 322–329
323
yielded very low enantioselectivity.20b The intention of fur-
ther exploring the synthetic applications and understand-
ing the mechanism of the powerful R. erythropolis AJ270
whole cell catalyst in organic chemistry led us to the cur-
rent study. Having considered the ready availability of
starting nitriles and the high catalytic efficiency and enantio-
selectivity of the biocatalyst, we envisaged that R. ery-
thropolis AJ270-catalyzed biotransformations of nitriles
might offer us a novel approach to optically active b3-
and b2-hydroxy and alkoxy acids and amide derivatives.
Herein, we report the microbial hydrolysis of two types
of racemic b-hydroxy and b-alkoxy nitriles and the obser-
vation of a dramatic O-substituent effect on the enantio-
selectivity of biocatalytic reactions.
ported in the literature, for example, biotransformations of
b-substituted b-hydroxy-a-methylenepropiononitriles,21 3-
hydroxy-4-aryloxy-butyronitriles,22 and 3-methyloxycar-
bonyl-3-benzyloxy propionitrile23 formed amide and acid
products with low ee values. It is widely believed that both
chemical and enzymatic reactions generally show poor chi-
ral induction when the substrates contain a stereogenic cen-
ter remote from the reaction site. To circumvent this
problem, we developed very recently a simple and powerful
protection/docking strategy.20 By the protection of a free
b-hydroxy of b-hydroxy alkanenitrile with a benzyl group,
for example, the enantioselectivity of an enzyme-catalyzed
reaction was increased dramatically. The benzyl group
probably acts as a docking moiety to enhance the chiral
interaction between the substrate and the enzyme, leading
therefore to a highly enantioselective biotransformation.
We applied this strategy in the current study by converting
substrate 1a into its O-benzylated form 1b. Unfortunately,
biotransformation of ( )-1b proceeded very sluggishly, and
only amide 2b and starting nitrile were isolated in 56% and
31% yields, respectively, after a week’s interaction with R.
erythropolis AJ270. No acid product 3b was observed (Ta-
ble 1, entry 2). The sharp contrast to the very efficient bio-
transformations of many b-benzyloxy alkanenitriles20
clearly suggests that the presence of a phenyl group rather
than an alkyl group in the substrates poses steric hindrance
to both nitrile hydratase and amidase within a microbial
cell. In other words, 3-benzyloxy-3-phenylpropionitrile 1b
and 3-benzyloxy-3-phenylpropionamide 2b were not ac-
cepted as good substrates by the nitrile hydratase and the
amidase, respectively, most probably due to their steric
bulkiness. Having realized the steric requirement of the en-
zymes toward the substrates, we then varied the O-substitu-
2. Results and discussion
To start our investigation, we first examined the R. ery-
thropolis AJ270 whole cell catalyzed hydrolysis of racemic
3-phenyl-3-hydroxypropionitrile ( )-1a, a b3-hydroxy car-
bonitrile substrate. Under very mild conditions, nitrile
( )-1a underwent a highly efficient hydrolysis to afford
amide 2a and acid 3a in almost quantitative yields. Disap-
pointingly, the enantiomeric excess (ee) values for amide
and acid products were found to be extremely low, indicat-
ing that the nitrile hydratase and amidase enzymes in-
volved within R. erythropolis AJ270 cell were almost non-
enantioselective against racemic nitrile ( )-1a and amide
( )-2a substrates, respectively (Table 1, entry 1). Such a
low enantioselectivity is not fully unexpected, however,
since most of the biotransformations of nitriles bearing a
b-stereogenic center gave very low enantioselectivity. As re-
Table 1. Biotransformations of racemic b3-hydroxy and b3-alkoxy nitriles 1a–da
OR
OR
OR
Rhodococcus erythropolis AJ270
CN
CONH2
+
CO2H
phosphate buffer, pH7.0, 30 o
C
Ph
Ph
R*-(+)-2a-d
Ph
S*-(-)-3a-d
(+/-)-1a-d
Entry
(
)-1
Time
2 (yield %)b (ee %)c
3 (yield %)b (ee %)c
Ed
1
1a R = H
0.5 h
7 d
2a (50) (1.6)
2b (56) (2.4)
3a (49) (4.0)
3b (0)
1.1
—
2e
3
1b R = Bn
1c R = Allyl
1d R = Me
1d R = Me
1d R = Me
1d R = Me
1d R = Me
1d R = Me
53 h
5.5 h
5.5 h
5.5 h
7 h
(R*)-2c (47) (40.0)
(R)-(+)-2d (49) (77.6)
(R)-(+)-2d (49) (68.8)
(R)-(+)-2d (47) (70.0)
(R)-(+)-2d (55) (69.4)
(R)-(+)-2d (55) (70.2)
(R)-(+)-2d (55) (60.8)
(S*)-3c (50) (29.4)
(S)-(ꢀ)-3d (51) (59.2)
(S)-(ꢀ)-3d (51) (45.6)
(S)-(ꢀ)-3d (51) (41.4)
(S)-(ꢀ)-3d (44) (52.0)
(S)-(ꢀ)-3d (44) (61.0)
(S)-(ꢀ)-3d (44) (63.2)
2.6
8.9
5.3
4.7
6.3
8.4
8.1
4
5f
6g
7h
8i
9j
5.5 h
11 h
a Biotransformation was carried out by incubating nitrile (1 mmol) in a suspension of Rhodococcus erythropolis AJ270 cells (2 g wet weight) in phosphate
buffer (50 mL, pH 7.0) at 30 °C.
b Isolated yield.
c Determined by HPLC analysis using a chiral column (see Section 4).
d Enantiomeric selection (E) was calculated according to a literature method.25
e Nitrile 1c was recovered (31% yield, ee 13.4%).
f pH 6.5 was applied.
g pH 7.5 was applied.
h Acetone (2 mL) was used as a co-solvent.
i b-Cyclodextrin (100 mg) was used as an additive.
j Incubation temperature was 20 °C.
* Stereochemistry is tentatively assigned.

324
D.-Y. Ma et al. / Tetrahedron: Asymmetry 19 (2008) 322–329
ent by choosing a smaller alkyl group. Introduction of an
alkyl group onto the free hydroxy of 1a resulted indeed
in the effective biotransformations with a slightly increased
enantioselectivity. Incubation of racemic nitrile ( )-1c with
biocatalyst for 53 h, for example, afforded amide (R*)-2c
and acid (S*)-3c in high yields with enantiomeric excesses
being 40.0% and 29.4%, respectively (entry 3, Table 1). A
further decrease in the size of the O-substituent led to faster
and more enantioselective biotransformations. As indi-
cated in entry 4, Table 1, effective biotransformations of
racemic 3-methoxy-3-phenylpropionitrile ( )-1d finished
within 5.5 h to yield quantitative yield of amide (R)-(+)-
2d and acid (S)-(ꢀ)-3d24 with enantiomeric excess values
being 77.6% and 59.2%, respectively. In comparison with
the biotransformations of nitrile ( )-1a (E25 = 1.1), the
enantioselectivity of biotransformations of ( )-1d
(E = 8.9) was improved more than 8-fold. Attempts were
made to further increase the enantioselectivity of the
reaction of 1d. In our previous studies, a slight change of
pH of the reaction media around 7.0,16,18a lower reaction
temperature such as at 20 °C,15e,16a,b and the addition of
acetone or b-cyclodextrin26 were found to increase the
enantioselectivity in some cases. As summarized in Table
1, however, variation of pH values of buffered reaction
media (entries 5 and 6), the addition of an organic
additive (entries 7 and 8), and the decrease of reaction
temperature (entry 9) had only a marginal effect on
enantioselectivity.
the closer the stereogenic center is to the reaction site, the
higher the chiral induction. The free hydroxy group was
then protected by several different substituents, and the ef-
fect of the O-substituent on the reaction efficiency and
enantioselectivity was examined. A large protection group
such as a TMS 4b or a benzyl group 4c led to a slow reac-
tion (Table 2, entries 2 and 3). The introduction of an allyl
group onto the free hydroxy of 4a also decreased the rate of
biotransformation, especially the amidase-mediated hydro-
lysis of amide 5d (Table 2, entry 4). Only under the condi-
tions halving the concentration of ( )-4d did the
biotransformations proceed within 36 h to afford optically
active amide (S*)-5d and acid (R*)-6d in excellent yields
(Table 2, entry 5). Surprisingly, the enantioselectivity of
the reaction of O-allylated substrate ( )-4d (E = 6)
decreased compared to the reaction of hydroxy-containing
substrate ( )-4a (E = 20) (entries 1 and 5). Gratifyingly,
when the hydroxy was protected by a methyl group, the
racemic nitrile substrate ( )-4e underwent highly efficient
and enantioselective biotransformations to furnish the cor-
responding amide (S)-(ꢀ)-5e and acid (R)-(+)-6e28 both in
a quantitative yield with excellent enantiomeric purity
(E = 193) (Table 2, entry 6). The enantioselectivity of the
reaction increased almost 10-fold (Table 2, entries 1 and 6).
The configurations of biocatalytically resolved products
(R)-3-methoxy-3-phenylpropionamide (R)-(+)-2d and
(S)-3-methoxy-3-phenylpropionic acid (S)-(ꢀ)-3d,24 (S)-2-
benzyl-3-hydroxypropionamide (S)-(ꢀ)-5a and (R)-2-benz-
yl-3-hydroxypropionic acid (R)-(+)-6a,26 and (S)-2-benzyl-
3-methoxy-propionamide amide (S)-(ꢀ)-5e and (R)-2-
benzyl-3-methoxy-propionic acid (R)-(+)-6e27 were deter-
mined by comparing the optical rotatory powers of
(S)-(ꢀ)-3d, (R)-(+)-6a, and (R)-(+)-6e with that of
authentic samples.24,26,27 The absolute configurations of
other biotransformation products including (R*)-2c,
(S*)-3c, (S*)-5c, (S*)-5d, and (R*)-6d were only assigned
tentatively, assuming that R. erythropolis AJ270 has the
same sense of enantioselection or enantiodifferentiation
against analogous substrates.
We then tuned our attention to the biotransformations of
racemic 2-hydroxymethyl-3-phenylpropionitrile 4a, a b2-
hydroxy carbonitrile species. Under identical incubation
conditions for the biotransformations of nitriles ( )-1a–d,
racemic nitrile ( )-4a underwent rapid and efficient bio-
transformations to produce optically active amide (S)-
(ꢀ)-5a and acid (R)-(+)-6a27 in excellent yield with moder-
ate enantioselectivity (E = 20) (Table 2, entry 1). It is worth
noting that the biotransformations of ( )-4a (Table 2, en-
try 1) gave higher enantioselectivity than that of ( )-1a
(Table 1, entry 1). This is in agreement with the notion that
Table 2. Biotransformations of racemic b2-hydroxy and b2-alkoxy nitriles 4a-ea
CN
CONH2
CO2H
OR
Rhodococcus erythropolis AJ270
Ph
Ph
Ph
+
phosphate buffer, pH 7.0, 30 oC
OR
OR
(R*)-6a-e
(
S*
)
-
5a-e
( )-4a-e
Entry
(
)-4 (mmol)
Time
5 (yield %)b (ee %)c
6 (yield %)b (ee %)c
Ed
20
—
—
—
1
4a R = H (1 mmol)
4b R = TMS (1 mmol)
4c R = Bn (1 mmol)
4d R = Allyl (2 mmol)
4d R = Allyl (1 mmol)
4e R = Me (2 mmol)
1.4 h
3 d
7 d
7 d
36 h
3.5 h
(S)-(ꢀ)-5a (43) (71.0)
5b (0)
(R)-(+)-6a (47) (81.1)
6b (0)
2e
3f
4
(S*)-(ꢀ)-5c (21) (68.4)g
(S*)-(+)-5d (72) (4.3)g
(S*)-(+)-5d (47) (57.6)g
(S)-(ꢀ)-5e (50) (96.2)
6c (0)
(R*)-6d (25) (62.8)g
(R*)-6d (51) (54.6)g
(R)-(+)-6e (50) (96.2)
5
6
6
193
a Biotransformation was carried out in a suspension of Rhodococcus erythropolis AJ270 cells (2 g wet weight) in phosphate buffer (50 mL, pH 7.0) at 30 °C.
b Isolated yield.
c Determined by HPLC analysis using a chiral column.
d Enantiomeric selection (E) was calculated according to a literature method.25
e Racemic nitrile ( )-4b (100%) was fully recovered.
f Nitrile 4c (66% yield, ee 12.4%) was recovered.
g Absolute configuration was tentatively assigned.

D.-Y. Ma et al. / Tetrahedron: Asymmetry 19 (2008) 322–329
325
The aforementioned results clearly indicated that the nat-
ure of the O-protecting group played an important role
in determining the enzymatic efficiency and enantioselectiv-
ity. In both 3-hydroxy-3-phenylpropionitrile and 2-hydrox-
ymehtyl-3-phenylpropionitrile cases, a large O-protecting
group such as a benzyl or a TMS had an inhibitory effect
on both nitrile hydratase and amidase, indicating the steric
limitation of the substrates accepted by both enzymes. The
introduction of an allyl group onto 3-hydroxy-3-phenyl-
propionitrile led to an increase in enantioselectivity while
the same O-protection in the case of 2-hydroxymethyl-3-
phenylpropionitrile had a negative effect in terms of enantio-
selectivity. O-Methylation in both 3-hydroxy-3-phenylpro-
pionitrile and 2-hydroxymethyl-3-phenylpropionitrile
substrates gave rise to a great increase in enantioselectivity.
The varied O-substituent effect suggested the importance of
choosing an O-protecting group. Based on the observation
of low ee values of recovered nitriles, and also according to
our early studies,15–21 the enhancement of enantioselectivi-
ty of overall nitrile biotransformations stems predomi-
nantly the high enantioselective amidase involved in R.
erythropolis AJ270. Although it is currently difficult to
rationalize the beneficial effect of O-methylation of the sub-
strates on the enantioselectivity because of the lack of a
structure of the amidase, the favorable match or recogni-
tion between the amidase and a sterically complementary
b-methoxy nitrile 1d, or particularly 4e, might account
for the high enantioselectivity.
method,29 and benzyl bromide (7.25 mL, 77.5 mmol) in
dichloromethane (30 mL). The mixture was stirred at room
temperature in the dark for 4 h and then filtrated. After the
removal of the solvent, column chromatography using a
silica gel eluted with a mixture of petroleum ether and ethyl
acetate (7:1) gave 3-benzyloxy-3-phenylpropionitrile 1b
1
(12.4 g, 74%) as a colorless liquid: H NMR (300 MHz,
CDCl3) d 7.32–7.43 (10H, m), 4.64 (1H, dd, J = 7.4,
5.5 Hz), 4.55 (1H, d, J = 12.0 Hz), 4.34 (1H, d, J =
12.0 Hz), 2.82 (1H, dd, J = 16.6, 7.4 Hz), 2.70 (1H, dd,
J = 16.6, 5.5 Hz); 13C NMR (75 MHz, CDCl3) d 138.8,
137.3, 129.1 (2C), 129.0, 128.6 (2C), 128.0, 127.2 (2C),
126.6 (2C), 117.2, 76.3, 70.8, 27.1 ppm; IR (KBr) m
2251 cmꢀ1 (CN); MS (EI) m/z (%) 197 (14) [Mꢀ40]+, 129
(14), 91 (100); Anal. Calcd for C16H15NO: C, 80.98; H,
6.37; N, 5.90. Found: C, 81.19; H, 6.37; N, 6.01.
4.1.2. Preparation of racemic 3-allyloxy-3-phenylpropioni-
trile 1c. A mixture of 3-hydroxy-3-phenylpropionitrile 1a
(294 mg, 2 mmol), acetone (4 mL), allyl bromide (0.51 mL,
6 mmol), and potassium carbonate (552 mg, 4 mmol) was
stirred at room temperature for 3 days and then filtered.
The filtrate was concentrated under vacuum and then sub-
jected to a silica gel column chromatography eluted by
petroleum ether and ethyl acetate (7:1). 3-Allyloxy-3-phen-
ylpropionitrile 1c (223 mg, 60%) was obtained as a color-
1
less liquid: H NMR (300 MHz, CDCl3) d 7.34–7.41 (5H,
m), 5.89 (1H, m), 5.23 (2H, m), 4.63 (1H, dd, J = 7.1,
5.6 Hz), 3.98 (1H, m), 3.84 (1H, m), 2.76 (1H, dd,
J = 16.6, 7.1 Hz), 2.69 (1H, dd, J = 16.6, 5.6 Hz); 13C
NMR (75 MHz, CDCl3) d 138.9, 133.9, 128.93 (2C),
128.88, 126.4 (2C) (MꢀC3H4), 117.7, 117.2, 76.3, 69.9,
27.0 ppm; IR (KBr) m 2251 cmꢀ1 (CN); MS (EI) m/z (%)
147 (100), 130 (76), 105 (58). Anal. Calcd for C12H13NO:
C, 76.98; H, 7.00; N, 7.48. Found: C, 76.84; H, 6.93; N,
7.66.
3. Conclusion
In conclusion, we have shown that R. erythropolis AJ270
whole cells can catalyze the hydrolysis of a number of b-hy-
droxy and b-alkoxy nitriles under very mild conditions.
Both the efficiency and enantioselectivity of biocatalysis,
however, were strongly dependent upon the structures of
both nitrile and amide substrates. We have demonstrated
an efficient approach to improve the enantioselectivity of
the biotransformations of b2- and b3-hydroxy nitriles by
simply methylating the free hydroxy group of b2- and b3-
hydroxy nitrile substrates. When the biotransformations
of 3-hydroxy-3-phenylpropionitrile and 2-hydroxymethyl-
3-phenylpropionitrile gave a low enantioselectivity, their
O-methylated isomers underwent highly efficient and enan-
tioselective biocatalytic reactions to afford highly enantio-
enriched b2- and b3-hydroxy amide and acid derivatives
in excellent yield. This study has provided an example of
a simple and very convenient substrate engineering method
to increase the performance of enzymes in terms of
enantioselectivity.
4.1.3. Preparation of racemic 3-methoxy-3-phenylpropioni-
trile 1d. Ag2O (4.6 g, 20 mmol) and methyl iodide (5 mL,
80 mmol) were added to 3-hydroxy-3-phenylpropionitrile
1a (2.94 g, 20 mmol) successively and the resulting mixture
was stirred in the dark overnight. The mixture was diluted
with acetone (5 mL) and filtered. After the removal of sol-
vent, column chromatography using a silica gel eluted with
a mixture of petroleum ether and ethyl acetate (10:1) gave
3-methoxy-3-phenylpropionitrile 1d30 (2.55 g, 79%) as a
1
colorless liquid: H NMR (300 MHz, CDCl3) d 7.32–7.43
(5H, m), 4.45 (1H, dd, J = 7.0, 5.6 Hz), 3.29 (3H, s), 2.77
(1H, dd, J = 16.6, 7.1 Hz), 2.68 (1H, dd, J = 16.6,
5.6 Hz); IR (KBr) m 2251 cmꢀ1 (CN).
4.1.4. Preparation of racemic 2-hydroxymethyl-3-phenylpro-
pionitrile 4a. To a suspension of methyl 2-cyano-3-phen-
ylacrylate31 (11.2 g, 60 mmol) in isopropanol (180 mL)
cooled in a water bath was added sodium borohydride
(6.84 g) and the resulting mixture was stirred overnight at
ambient temperature. Acetic acid (30%) was carefully
added to the reaction mixture to quench the unconsumed
sodium borohydride until no bubbling was observed. 2-
Propanol was then removed under vacuum and the residue
was basified to pH 10 with aqueous sodium hydroxide
(1 M) and extracted with diethyl ether (3 ꢁ 50 mL). After
4. Experimental
4.1. Preparation of starting nitriles and their spectroscopic
data
4.1.1. Preparation of racemic 3-benzyloxy-3-phenylpropio-
nitrile 1b. Ag2O (24.5 g, 105 mmol) was added to a mix-
ture of 3-hydroxy-3-phenylpropionitrile 1a (10.37 g,
70.5mmol), which was prepared following a literature

326
D.-Y. Ma et al. / Tetrahedron: Asymmetry 19 (2008) 322–329
drying over with anhydrous MgSO4 and removal of sol-
vent, 2-hydroxymethyl-3-phenylpropionitrile 4a32 (9.44 g,
98%) was isolated as a colorless liquid: 1H NMR
(300 MHz, CDCl3) d 7.35–7.24 (5H, m), 3.77 (2H, s),
2.97 (3H, s), 2.29 (1H, br); 13C NMR (75 MHz, CDCl3) d
136.4, 129.0, 128.9, 127.4, 120.5, 61.8, 36.8, 34.5 ppm; IR
(KBr) m 3450 (OH), 2245 cmꢀ1 (C@O).
72.3, 68.3, 34.8, 34.3 ppm; IR (KBr) m 2243 cmꢀ1 (CN);
MS (EI) m/z (%) 201 (19) [M]+, 170 (6), 143 (89), 130
(100), 91 (65); Anal. Calcd for C13H15NO: C, 77.58; H,
7.51; N, 6.96. Found: C, 77.62; H, 7.49; N, 6.93.
4.1.8. Preparation of racemic 2-methoxymethyl-3-phenyl-
propionitrile 4e. Ag2O (5.8 g, 25 mmol) and methyl iodide
(6.23 mL, 100 mmol) were added to a mixture of 2-
hydroxymethyl-3-phenylpropionitrile 4a (4.03 g, 25 mmol)
and acetonitrile (25 mL) successively and the resulting mix-
ture was stirred in the dark overnight after which the mix-
ture was filtered. After the removal of the solvent, column
chromatography using a silica gel eluted with a mixture of
petroleum ether and ethyl acetate (20:1) gave 2-methoxy-
methyl-3-phenylpropionitrile 4e (3.39 g, 77%) as a colorless
4.1.5. Preparation of racemic 3-phenyl-2-(trimethylsilyl-
methyl)propionitrile 4b. A mixture of HMDS (1.45 g,
9 mmol) and 2-hydroxymethyl-3-phenylpropionitrile 4a
(1.93 g, 12 mmol) was stirred at room temperature for
5 min and then passed through a silica gel column chroma-
tography eluted with a mixture of petroleum ether and
ethyl acetate (100:1). 3-Phenyl-2-(trimethylsilylmethyl)pro-
pionitrile 4b (1.75 g, 63%) was obtained as a colorless
1
liquid: H NMR (300 MHz, CDCl3) d 7.23–7.37 (5H, m),
1
liquid: H NMR (300 MHz, CDCl3) d 7.08–7.20 (5H, m),
3.48 (2H, d, J = 5.3 Hz), 3.40 (3H, s), 2.99 (3H, m); 13C
NMR (75 MHz, CDCl3) d 136.5, 129.1 (2C), 128.8 (2C),
127.3, 120.3, 70.8, 59.2, 34.8, 34.2 ppm; IR (KBr) m
2241 cmꢀ1 (CN); MS (EI) m/z (%) 175 (11) [M]+, 143
(100), 116 (13), 91 (65); Anal. Calcd for C11H13NO: C,
75.40; H, 7.48; N, 7.99. Found: C, 75.53; H, 7.35; N, 8.13.
3.54 (2H, d, J = 5.1 Hz), 2.74–2.81 (3H, m), 0.00 (9H, s);
13C NMR (75 MHz, CDCl3) d 137.3, 129.7 (2C), 129.3
(2C), 127.8, 62.3, 37.3, 35.1, 0.0 ppm; MS (EI) m/z (%)
233 (5) [M]+, 218 (100), 188 (43), 143 (37), 91 (24); Anal.
Calcd for C13H19NSi (C, H, N): C, 66.90; H, 8.21; N,
6.00. Found: C, 66.87; H, 7.80; N, 6.10.
4.2. General procedure for the biotransformations of nitriles
4.1.6. Preparation of racemic 2-benzyloxymethyl-3-phenyl-
propionitrile 4c. Ag2O (5.8 g, 25 mmol) was added to a
mixture of 2-hydroxymethyl-3-phenylpropionitrile 4a
(4.03 g, 25 mmol) and benzyl bromide (4.5 mL, 37.5 mmol)
in 25 mL dichloromethane. The mixture was stirred at
room temperature in the dark for 28 h and then filtered.
After the removal of solvent, column chromatography
using a silica gel eluted with a mixture of petroleum ether
and ethyl acetate (15:1) gave 2-benzyloxymethyl-3-phenyl-
propionitrile 4c (2.84 g, 45%) as a colorless liquid: 1H
NMR (300 MHz, CDCl3) d 7.23–7.38 (10H, m), 4.58
(2H, s), 3.57 (2H, d, J = 5.4 Hz), 2.98 (3H, m); 13C NMR
(75 MHz, CDCl3) d 137.3, 136.4, 129.1 (2C), 128.8 (2C),
128.6 (2C), 128.0, 127.8 (2C), 127.3, 120.2, 73.4, 68.3,
34.8, 34.5 ppm; IR (KBr) m 2248 cmꢀ1 (CN); MS (EI)
m/z (%) 251 (8) [M]+, 220 (10), 181 (6), 160 (3), 143 (11),
134 (13), 130 (20), 91 (100); Anal. Calcd for C17H17NO:
C, 81.24; H, 6.82; N, 5.57. Found: C, 81.15; H, 6.79; N,
5.68.
To an Erlenmeyer flask (150 mL) with a screw cap were
added R. erythropolis AJ270 cells14,15a (2 g wet weight)
and potassium phosphate buffer (0.1 M, pH 7.0, 50 mL),
and the resting cells were activated at 30 °C for 0.5 h with
orbital shaking. Racemic nitrile was added in one portion
to the flask and the mixture was incubated at 30 °C using
an orbital shaker (200 rpm). The reaction, monitored by
TLC and HPLC, was quenched after a specified period
of time (see Tables 1 and 2) by removing the biomass
through a Celite pad filtration. The resulting aqueous solu-
tion was basified to pH 12 with aqueous NaOH (2 M).
Extraction with ethyl acetate (3ꢁ60 mL) gave, after drying
over MgSO4, concentration, and a silica gel column chro-
matography eluted with a mixture of petroleum ether and
acetone (2:1), the amide product. The aqueous solution
was then acidified using aqueous HCl (2 M) to pH 2 and
extracted with ethyl acetate (3ꢁ60 mL). The acid product
was obtained after drying over with MgSO4, removal of
the solvent under vacuum, followed by silica gel column
chromatography eluted with a mixture of petroleum ether
and acetone (from 20:1 to 2:1). All products were charac-
terized by their spectral data and comparison of the melt-
ing points and specific rotation values with those of the
known compounds, which are listed as follows, or by full
characterization. Enantiomeric excess values were obtained
from HPLC analysis using a column of chiral stationary
phase.
4.1.7. Preparation of racemic 3-allyloxy-3-phenylpropioni-
trile 4d. At 0 °C, allyl bromide (220 lL, 2.5 mmol) was
added to a suspension of NaH (72 mg, 3 mmol) in dry
DMF (2 mL). A solution of 2-hydroxymethyl-3-phenylpro-
pionitrile 4a (322 mg, 2 mmol) in dry DMF (2 mL) was
added dropwise into the mixture. After stirring for 1 h,
the reaction was quenched with saturated aqueous NaH-
CO3. An additional 40 mL of water was added to the mix-
ture and extracted with diethyl ether (3 ꢁ 15 mL). After
drying over with anhydrous MgSO4 and removal of sol-
vent, 3-allyloxy-3-phenylpropionitrile 4d (310 mg, 77%)
was isolated by silica gel column chromatography eluted
with petroleum ether and ethyl acetate (50:1) as a colorless
4.2.1. 3-Hydroxy-3-phenylpropionamide 2a.33 Mp 122–
25
123 °C; ½aꢂD ¼ 0 (c 2.40, CHCl3); ee 1.6% (chiral HPLC
analysis using a Chiralcel OJ column with a mixture of hex-
ane and 2-propanol (95:5) at a flow rate 0.8 mL/min as the
mobile phase, oven temperature 25 °C, tminor = 52.1 min,
tmajor = 59.6 min); 1H NMR (300 MHz, DMSO-d6) d
7.15–7.35 (6H, m), 6.82 (1H, br), 5.38 (1H, br), 4.91–4.96
(1H, m), 2.41 (1H, dd, J = 14.3, 8.4 Hz), 2.34 (1H, dd,
J = 14.3, 5.1 Hz); 13C NMR (75 MHz, DMSO-d6) d
1
liquid: H NMR (300 MHz, CDCl3) d 7.24–7.35 (5H, m),
5.90 (1H, m), 5.31 (1H, dd, J = 17.2, 1.6 Hz), 5.23 (1H,
dd, J = 10.4, 1.4 Hz), 4.05 (2H, m), 3.54 (2H, d,
J = 5.3 Hz), 2.99 (3H, m); 13C NMR (75 MHz, CDCl3) d
136.5, 133.9, 129.1 (2C), 128.8 (2C), 127.3, 120.2, 117.8,

D.-Y. Ma et al. / Tetrahedron: Asymmetry 19 (2008) 322–329
327
172.2, 145.3, 127.9, 126.7, 125.7, 69.5, 45.2 ppm; IR (KBr)
m 3393, 3181 (OH, CONH2), 1653 (C@O), 1623 cmꢀ1; MS
(EI) m/z (%) 165 (3) [M]+, 147 (27), 146 (54), 129 (87), 106
(100), 105 (99), 77 (81); Anal. Calcd for C9H11NO2: C,
65.44; H, 6.71; N, 8.48. Found: C, 65.40; H, 6.68; N, 8.47.
(1H, m), 5.15–5.26 (2H, m), 4.81 (1H, dd, J = 9.3,
4.4 Hz), 3.91–4.02 (1H, m), 3.79–3.84 (1H, m), 2.88 (1H,
dd, J = 15.7, 9.3 Hz), 2.66 (1H, dd, J = 15.7, 4.4 Hz); 13C
NMR (75 MHz, CDCl3) d 175.9, 140.3, 134.3, 128.7,
128.2, 126.6, 117.3, 77.2, 69.7, 43.3 ppm; IR (KBr) m
3068–2577 (COOH), 1706 cmꢀ1 (C@O); MS (EI) m/z (%)
206 (2) [M]+, 165 (6), 150 (9), 147 (12), 131 (3), 104
(100); Anal. Calcd for C12H14O3: C, 69.88; H, 6.84. Found:
C, 69.94; H, 6.88.
4.2.2. 3-Hydroxy-3-phenylpropionic acid 3a.34 Mp 94–
25
95 °C; ½aꢂD ¼ 0 (c 1.40, CHCl3); ee 4.0% (chiral HPLC
analysis of the corresponding benzyl ester using a Chiralcel
OD column with a mixture of hexane and 2-propanol (9:1)
at a flow rate 0.8 mL/min as the mobile phase, oven tem-
perature 25 °C, tminor = 17.5 min, tmajor = 21.4 min); 1H
NMR (300 MHz, CDCl3) d 7.29–7.38 (5H, m), 5.16 (1H,
dd, J = 8.9, 4.0 Hz), 4.91 (2H, br), 2.85 (1H, dd,
J = 16.5, 8.9 Hz), 2.76 (1H, dd, J = 1.65, 4.0 Hz); IR
(KBr) m 3291 (OH), 3069–2542 (COOH), 1699 cmꢀ1
(C@O); MS (EI) m/z (%) 166 (2) [M]+, 147 (20), 129 (17),
104 (100); Anal. Calcd for C9H10O3: C, 65.05; H, 6.07.
Found: C, 65.11; H, 6.12.
4.2.6. (R)-3-Methoxy-3-phenylpropionamide 2d.24 Mp
25
69–71 °C; ½aꢂD ¼ þ111:9 (c 3.20, CHCl3); ee >99% (chiral
HPLC analysis using a Chiralcel OD column with a mix-
ture of hexane and 2-propanol (9:1) at a flow rate
0.8 mL/min as the mobile phase, oven temperature 25 °C,
1
tmajor = 16.7 min, tminor = 20.7 min); H NMR (300 MHz,
CDCl3) d 7.27–7.39 (5H, m), 6.25 (1H, br), 5.84 (1H, br),
4.59 (1H, dd, J = 9.6, 3.4 Hz), 3.25 (3H, s), 2.70 (1H, dd,
J = 14.9, 9.6 Hz), 2.46 (1H, dd, J = 14.9, 3.4 Hz); 13C
NMR (75 MHz, CDCl3) d 173.2, 140.6, 128.7, 128.1,
126.4, 80.4, 56.8, 45.0 ppm; IR (KBr) m 3369, 3195
(CONH2), 1671 cmꢀ1 (C@O); MS (EI) m/z (%) 179 (3)
[M]+, 164 (26), 147 (25), 146 (33), 129 (100), 121 (47),
103 (31), 102 (30); Anal. Calcd for C10H13NO2: C, 67.02;
H, 7.31; N, 7.82. Found: C, 66.99; H, 7.43; N, 7.75.
4.2.3. 3-Benzyloxy-3-phenylpropionamide 2b. Mp 104–
25
105 °C; ½aꢂD ¼ 0 (c 2.50, CHCl3); ee 2.4% (chiral HPLC
analysis using a Chiralcel OD column with a mixture of
hexane and 2-propanol (9:1) at a flow rate 0.8 mL/min as
the mobile phase, oven temperature 25 °C, tminor = 32.7
min, tmajor = 36.3 min); 1H NMR (300 MHz, CDCl3) d
7.25–7.42 (10H, m), 6.15 (1H, br), 5.62 (1H, br), 4.82
(1H, dd, J = 9.5, 3.5 Hz), 4.46 (1H, d, J = 11.3 Hz), 4.32
(1H, d, J = 11.3 Hz), 2.76 (1H, dd, J = 14.9, 9.5 Hz), 2.50
(1H, dd, J = 14.9, 3.5 Hz); 13C NMR (75 MHz, CDCl3) d
173.0, 140.7, 137.7, 128.8, 128.5, 128.2, 127.94, 127.89,
126.5, 78.4, 71.0, 45.2 ppm; IR (KBr) m 3331, 3168
(CONH2), 1662 (C@O), 1641 cmꢀ1; MS (EI) m/z (%) 237
(2) [Mꢀ18]+, 197 (2), 180 (2), 179 (2), 164 (6), 149 (34),
147 (34), 146 (80), 131 (29), 129 (100); Anal. Calcd for
C16H17NO2: C, 75.27; H, 6.71; N, 5.49. Found: C, 75.01;
H, 6.70; N, 5.53.
4.2.7. (S)-3-Methoxy-3-phenylpropionic acid 3d.24 Mp
25
65–66 °C; ½aꢂD ¼ ꢀ41:5 (c 1.83, CHCl3); ee 64.5% (chiral
HPLC analysis using a Chiralcel OD column with a mix-
ture of hexane and 2-propanol (9:1) and 0.1% HOAc at a
flow rate 0.8 mL/min as the mobile phase, oven tempera-
ture 25 °C, tmajor = 8.0 min, tminor = 10.6 min) {lit.24
1
[a] = ꢀ49.3 (c 0.3, CHCl3)}; H NMR (300 MHz, CDCl3)
d 7.29–7.40 (5H, m), 4.63 (1H, dd, J = 9.4, 4.3 Hz), 3.25
(3H, s), 2.84 (1H, dd, J = 15.6, 9.4 Hz), 2.64 (1H, dd,
J = 15.6, 4.3 Hz); 13C NMR (75 MHz, CDCl3) d 176.2,
140.1, 128.7, 128.2, 126.6, 79.8, 56.8, 43.2 ppm; IR (KBr)
m 3063–2582 (COOH), 1710 (C@O), 1650 cmꢀ1; MS (EI)
m/z (%) 180 (4) [M]+, 165 (4), 148 (5), 147 (7), 131 (5),
121 (63), 104 (100), 103 (77); Anal. Calcd for C10H12O3:
C, 66.65; H, 6.71. Found: C, 66.73; H, 6.94.
4.2.4. (R*)-3-Allyloxy-3-phenylpropionamide 2c. Mp 69–
25
70 °C; ½aꢂD ¼ 0 (c 1.50, CHCl3); ee 40.0% (chiral HPLC
analysis using a Chiralcel OJH column with a mixture of
hexane and 2-propanol (9:1) at a flow rate 0.5 mL/min as
the mobile phase, oven temperature 25 °C, tminor = 22.4
min, tmajor = 26.5 min); 1H NMR (300 MHz, CDCl3) d
7.26–7.39 (5H, m), 6.25 (1H, br), 5.85–5.96 (1H, m), 5.46
(1H, br), 5.16–5.26 (2H, m), 4.76 (1H, dd, J = 9.6,
3.4 Hz), 3.93–4.02 (1H, m), 3.80–3.86 (1H, m), 2.74 (1H,
dd, J = 14.9, 9.6 Hz), 2.44 (1H, dd, J = 14.9, 3.4 Hz); 13C
NMR (75 MHz, CDCl3) d 172.9, 140.8, 134.2, 128.7,
128.1, 126.4, 117.3, 78.1, 69.7, 45.1 ppm; IR (KBr) m
3403, 3201 (CONH2), 1654 cmꢀ1 (C@O); MS (EI) m/z
(%) 205 (2) [M]+, 164 (77), 147 (73), 146 (39), 129 (100),
105 (71); Anal. Calcd for C12H15NO2: C, 70.22; H, 7.37;
N, 6.82. Found: C, 70.35; H, 7.39; N, 6.83.
4.2.8. (S)-2-Hydroxymethyl-3-phenylpropionamide 5a. Mp
25
127–130 °C; ½aꢂD ¼ ꢀ31:3 (c 6.08, EtOH); ee 65.4% (chiral
HPLC analysis using a Chiralcel AD column with a mix-
ture of hexane and 2-propanol (85:15) at a flow rate
0.6 mL/min as the mobile phase, oven temperature 25 °C,
1
tmajor = 10.2 min, tminor = 12.6 min); H NMR (300 MHz,
DMSO-d6) d 7.14–7.43 (6H, m), 6.76 (1H, br), 4.73 (1H,
t, J = 5.1 Hz), 3.35–3.56 (2H, m), 2.51–2.73 (3H, m); 13C
NMR (75 MHz, DMSO-d6) d 175.2, 140.1, 128.7, 128.1,
125.8, 62.4, 50.2, 34.4 ppm; IR (KBr) m 3385 (OH), 3221
(CONH2), 1690 (C=O), 1641 cmꢀ1; MS (EI) m/z (%) 179
(12) [M]+, 161 (71), 148 (100), 131 (64), 117 (54), 91 (63);
Anal. Calcd for C10H13NO2: C, 67.02; H, 7.31; N, 7.82.
Found: C, 66.84; H, 7.30; N, 7.74.
4.2.5. (S*)-3-Allyloxy-3-phenylpropionic acid 3c. Mp 66–
25
67 °C; ½aꢂD ¼ 0 (c 2.00, CHCl3); ee 29.4% (chiral HPLC
analysis of the corresponding methyl ester using a Chiralcel
OD column with a mixture of hexane and 2-propanol (9:1)
at a flow rate 0.8 mL/min as the mobile phase, oven tem-
perature 25 °C, tmajor = 5.8 min, tminor = 9.0 min); 1H
NMR (300 MHz, CDCl3) d 7.31–7.40 (5H, m), 5.82–5.99
4.2.9. (R)-2-Hydroxymethyl-3-phenylpropionic acid 6a.26
25
Mp 65–66 °C; ½aꢂD ¼ þ13:5 (c 3.10, CHCl3); ee 86.4% (chi-
ral HPLC analysis of the corresponding methyl ester using
a Chiralcel ODH column with a mixture of hexane and 2-
propanol (95:5) at a flow rate 0.8 mL/min as the mobile

328
D.-Y. Ma et al. / Tetrahedron: Asymmetry 19 (2008) 322–329
phase, oven temperature 20 °C, tmajor = 21.2 min, tminor
=
mixture of hexane and 2-propanol (9:1) at a flow rate
23.3 min) {lit.26 (R)-2-hydroxymethyl-3-phenylpropionic
0.8 mL/min as the mobile phase, oven temperature 25 °C,
25
acid, ½aꢂD ¼ þ15:9 (c 1.14, CHCl3)}; 1H NMR
tmajor = 10.2 min, tminor = 13.9 min); H NMR (300 MHz,
1
(300 MHz, CDCl3) d 7.25–7.35 (5H, m), 6.96 (1H, br),
3.71–3.84 (2H, m), 2.84–3.14 (3H, m); 13C NMR
(75 MHz, CDCl3) d 179.8, 138.2, 129.0, 128.6, 126.7,
61.9, 48.9, 34.0 ppm; IR (KBr) m 3341 (OH), 3107–2519
(COOH), 1698 cmꢀ1 (C@O); MS (EI) m/z (%) 180 (2)
[M]+, 162 (92), 144 (16), 131 (28), 117 (100), 91 (56); Anal.
Calcd for C10H12O3: C, 66.65; H, 6.71. Found: C, 66.67; H,
6.68.
CDCl3) d 7.19–7.32 (5H, m), 6.12 (1H, br), 5.66 (1H, br),
3.45 (2H, d, J = 5.6 Hz), 3.33 (3H, s), 3.03 (1H, dd,
J = 13.4, 6.9 Hz), 2.62–2.81 (2H, m); 13C NMR (75 MHz,
CDCl3) d 176.2, 139.1, 129.0, 128.5, 126.4, 72.2, 59.0,
48.7, 34.8 ppm; IR (KBr) m 3329, 3194 (CONH2),
1666 cmꢀ1 (C@O); MS (EI) m/z (%) 193 (14) [M]+, 161
(21), 148 (100), 131 (75), 117 (36), 91 (18); Anal. Calcd
for C11H15NO2: C, 68.37; H, 7.82; N, 7.25. Found: C,
68.39; H, 7.97; N, 7.33.
4.2.10. (S*)-2-Benzyloxymethyl-3-phenylpropionamide 5c.
25
4.2.14. (R)-2-Methoxymethyl-3-phenylpropionic acid 6e27.
Mp 80–81 °C; ½aꢂD ¼ ꢀ10:0 (c 2.39, CHCl3); ee 68.4% (chi-
25
25
ral HPLC analysis using a Chiralcel ADH column with a
mixture of hexane and 2-propanol (9:1) at a flow rate
0.5 mL/min as the mobile phase, oven temperature 25 °C,
Oil; ½aꢂD ¼ þ4:0 (c 6.74, cyclohexane); ½aꢂD ¼ þ7:3 (c 5.74,
CHCl3); ee 96.2% (chiral HPLC analysis of the correspond-
ing methyl ester using a Chiralcel OJH column with a mix-
ture of hexane and 2-propanol (9:1) at a flow rate 0.5 mL/
1
tminor = 22.4 min, tmajor = 24.6 min); H NMR (300 MHz,
CDCl3) d 7.10–7.27 (10H, m), 6.11 (1H, br), 5.62 (1H,
br), 4.41 (2H, s), 3.49 (2H, d, J = 5.9 Hz), 2.94 (1H, dd,
J = 13.2, 6.7 Hz), 2.60–2.76 (2H, m); 13C NMR (75 MHz,
CDCl3) d 176.4, 139.0, 137.6, 129.0, 128.5 (4C), 127.9,
127.8, 126.5, 73.5, 69.8, 48.7, 34.9 ppm; IR (KBr) m 3376,
3197 (CONH2), 1655 (C@O), 1641, 1620 cmꢀ1; MS (EI)
m/z (%) 269 (5) [M]+, 251 (5), 148 (70), 131 (24), 117
(51), 91 (100); Anal. Calcd for C17H19NO2: C, 75.81; H,
7.11; N, 5.20. Found: C, 75.75; H, 7.13; N, 5.33.
min as the mobile phase, oven temperature 25 °C, tmajor
=
17.4 min, tminor = 21.0 min) {lit.27 (S)-2-methoxymethyl-3-
25
phenylpropionic acid, ½aꢂD ¼ ꢀ4 (c 1.05, cyclohexane)};
1H NMR (300 MHz, CDCl3) d 11.23 (1H, br), 7.18–7.31
(5H, m), 3.47–3.56 (2H, m), 3.33 (3H, s), 2.81–3.05 (3H,
m); 13C NMR (75 MHz, CDCl3) d 179.6, 138.4, 129.0,
128.5, 126.6, 71.9, 59.0, 47.4, 34.2 ppm; IR (KBr) m 3084–
2572 (COOH), 1740, 1710 (C@O) cmꢀ1; MS (EI) m/z (%)
194 (2) [M]+, 162 (100), 148 (14), 144 (19), 131 (23), 117
(78), 91 (33); Anal. Calcd for C11H14O3: C, 68.02; H,
7.27. Found: C, 67.64; H, 7.30.
4.2.11. (S*)-2-Allyloxymethyl-3-phenylpropionamide 5d.
25
Mp 46–48 °C; ½aꢂD ¼ þ2:8 (c 4.27, CHCl3); ee 57.6% (chi-
ral HPLC analysis using a Chiralcel ADH column with a
mixture of hexane and 2-propanol (9:1) at a flow rate
0.5 mL/min as the mobile phase, oven temperature 25 °C,
Acknowledgments
1
We thank the State Major Fundamental Research Program
(2003CB716005, 2006CB806106), the National Natural
Science Foundation of China, and the Chinese Academy
of Sciences for financial support.
tmajor = 17.9 min, tminor = 21.9 min); H NMR (300 MHz,
CDCl3) d 7.18–7.30 (5H, m), 6.28 (1H, br), 6.04 (1H, br),
5.80–5.93 (1H, m), 5.15–5.28 (2H, m), 3.94–4.04 (2H, m),
3.47–3.52 (2H, m), 2.99–3.05 (1H, m), 2.68–2.82 (2H, m);
13C NMR (75 MHz, CDCl3) d 176.6, 139.1, 134.2, 129.0,
128.5, 126.4, 117.4, 72.2, 69.8, 48.6, 34.9 ppm; IR (KBr) m
3341, 3199 (CONH2), 1667 cmꢀ1 (C@O); MS (EI) m/z
(%) 219 (7) [M]+, 161 (32), 148 (100), 131 (39), 117 (52),
91 (24); Anal. Calcd for C13H17NO2: C, 71.21; H, 7.81;
N, 6.39. Found: C, 71.47; H, 7.89; N, 6.59.
References
1. (a) Noyori, R. Asymmetric Catalysis in Organic Synthesis;
John Wiley & Sons, 1994, pp 56–82; For recent examples, see:
(b) Li, K. W.; Wu, J.; Xing, W.; Simon, J. A. J. Am. Chem.
Soc. 1996, 118, 7237; (c) Labeeuw, O.; Blanc, D.; Phansavath,
P.; Ratovelomanana-Vidal, V.; Genet, J.-P. Eur. J. Org.
Chem. 2004, 2352; (d) Herb, C.; Bayer, A.; Maier, M. E.
Chem. Eur. J. 2004, 10, 5649.
4.2.12. (R*)-2-Allyloxymethyl-3-phenylpropionic acid 6d.
25
Oil; ½aꢂD ¼ 0 (c 3.10, CHCl3); ee 54.6% (chiral HPLC anal-
ysis using a Chiralcel ADH column with a mixture of hex-
ane and 2-propanol (9:1) at a flow rate 0.5 mL/min as the
mobile phase, oven temperature 25 °C, tminor = 12.9 min,
tmajor = 16.0 min); 1H NMR (300 MHz, CDCl3) d 10.85
(1H, br), 7.22–7.35 (5H, m), 5.75–6.00 (1H, m), 5.20–5.32
(2H, m), 4.01 (2H, d, J = 5.5 Hz), 3.56–3.66 (2H, m),
2.88–3.11 (3H, m); 13C NMR (75 MHz, CDCl3) d 179.5,
138.5, 134.3, 129.0, 128.5, 126.6, 117.3, 72.2, 69.3, 47.5,
34.3 ppm; IR (KBr) m 3091–2600 (COOH), 1710 cmꢀ1
(C@O); MS (EI) m/z (%) 220 (4) [M]+, 162 (100), 144
(13), 131 (30), 117 (55), 91 (23); Anal. Calcd for
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25
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D.-Y. Ma et al. / Tetrahedron: Asymmetry 19 (2008) 322–329
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