Microbial whole cell-catalyzed desymmetrization of prochiral malonamides: Practical synthesis of enantioenriched functionalized carbamoylacetates and their application in the preparation of unusual α-amino acids

Article abstract of DOI:10.1016/j.tet.2011.05.103

Catalyzed by Rhodococcus erythropolis AJ270, an amidase-containing microbial whole cell catalyst, under very mild conditions, a number of functionalized prochiral malonamides underwent enantioselective desymmetrization reaction to afford high yield of car

Full text of DOI:10.1016/j.tet.2011.05.103

Tetrahedron 67 (2011) 5604e5609
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Microbial whole cell-catalyzed desymmetrization of prochiral malonamides:
practical synthesis of enantioenriched functionalized carbamoylacetates and their
application in the preparation of unusual a-amino acids
,b,
Li-Bin Zhang a, De-Xian Wang a, Mei-Xiang Wang a
*
a Beijing National Laboratory for Molecular Sciences, CAS Key Laboratory of Molecular Recognition and Function, Institute of Chemistry, Chinese Academy of Sciences,
Beijing 100190, China
b The Key Laboratory of Bioorganic Phosphorus Chemistry and Chemical Biology, Ministry of Education, Department of Chemistry, Tsinghua University,
Beijing 100084, China
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 11 April 2011
Received in revised form 17 May 2011
Accepted 24 May 2011
Available online 30 May 2011
Catalyzed by Rhodococcus erythropolis AJ270, an amidase-containing microbial whole cell catalyst, under
very mild conditions, a number of functionalized prochiral malonamides underwent enantioselective
desymmetrization reaction to afford high yield of carbamoylacetic acids with moderate to excellent
enantioselectivity. The synthetic application has been demonstrated with a multi-gram scale biocatalytic
preparation of R-(ꢀ)-
substituted -amino acids of the interest of medicinal chemistry.
Ó 2011 Elsevier Ltd. All rights reserved.
a-allyl-a-methyl-carbamoylacetic acid and its conversions to varied a,a-di-
a
1. Introduction
catalyst able to hydrolyze various racemic nitriles and amides.
While the nitrile hydratase exhibits low or none enantioselectivity,
the amidase involved in cell is highly enantioselective.5 By means of
Rh. erythropolis AJ270-catalyzed hydrolysis of nitriles and amides,
a large number of enantioenriched carboxamides and carboxylic
acids have been prepared.5e11 To further explore the application of
Rh. erythropolis AJ270 in organic synthesis, and to gain insight into
the catalytic property of the amidase against prochiral diamides,
we undertook the current study. We report herein the enantiose-
lective bio-desymmetrization reaction of functionalized prochiral
malonamides. Practical biocatalytic synthesis of highly enantio-
Desymmetrization of prochiral molecules constitutes an im-
portant strategy for the synthesis of chiral molecules. Biocatalytic
desymmetrization of prochiral diols and diesters using lipases, es-
terases, and acylases, for example, has been widely used to prepare
chiral products that are hardly accessible by other methods.1 Am-
idase [3.5.1.4] is a type of hydrolytic enzyme catalyzing the hy-
drolysis of amides to produce carboxylic acids. A large number of
studies have demonstrated that amidases derived from different
microorganisms show a broad substrate spectrum and good
enantioselectivity against racemic substrates. Amidases have been
applied therefore to catalyze the kinetic resolution of a wide variety
of racemic amides.2 Surprisingly, the amidase-catalyzed selective
desymmetrization of prochiral diamides has remained largely un-
explored.2,3 To the best of our knowledge, there is only one litera-
merically pure
gram scale and its application in the preparation of unusual
-disubstituted -amino acids are also demonstrated.
a-allyl-a-methyl-carbamoylacetic acid in a multi-
a,
a
a
2. Results and discussion
ture report in which Wu and Li3 described in 2003 that
a-methyl-a-
arylmethylmalonamides undergo biocatalytic hydrolysis to yield
chiral malonamic acids with high enantioselectivity. Since the
substrate structures are simple and not functionalized, synthetic
applications are limited.
Rhodococcus erythropolis AJ270 is a nitrile hydratase/amidase-
containing microorganism.4 It has been shown in the past decade
that Rh. erythropolis AJ270 is a powerful microbial whole cell
We initiated our study with the examination of the bio-
transformation of prochiral
a-allyl-a-methylmalonamide 1a
(Scheme 1). In the presence of Rh. erythropolis AJ270 whole cell
catalyst in an aqueous phosphate buffer (pH¼7.0), hydrolysis of 1a
was found to proceed efficiently at 30 ꢁC. To facilitate the isolation
of product, acid product was converted into methyl ester 2a using
diazomethane. As indicated in Table 1, enantioenriched carba-
moylacetic ester (ꢀ)-2a was obtained in 85% with ee of 90.7% in
0.5 h (entry 1, Table 1). Rh. erythropolis AJ270 was able to catalyze
the desymmetrization reaction of 1a at a lower temperature. For
example, when biotransformation was conducted at 20 ꢁC and
* Corresponding author. E-mail address: wangmx@mail.tsinghua.edu.cn
(M.-X. Wang).
0040-4020/$ e see front matter Ó 2011 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tet.2011.05.103

L.-B. Zhang et al. / Tetrahedron 67 (2011) 5604e5609
5605
10 ꢁC, the ee values of the product (ꢀ)-2a was improved to 93.8%
and 95.0%, respectively, albeit the reaction rate was slightly de-
creased (entries 2 and 3, Table 1).
contain an a-methyl group, for instance, introduction of an
alkenyl substituent, such as allyl (1a), E-but-2-enyl (1e), and
cinnamyl (1g), or a benzyl group (1b) gave rise to highly enan-
tioselective biotransformation (entries 1e4, 7, and 9, Table 1). The
presence of a saturated a-propyl group (1c) or a prop-2-ynyl (1f),
a carbonecarbon triple bond moiety, led to the alleviation of
enantiocontrol of the reactions (entries 5 and 8). Surprisingly,
reaction of a-(2-methylallyl)-substituted substrate 1d, an isomer
O
O
1. cell catalyst
2. MeI or CH2N2
or PhCH2Br
C
R1 CNH2
R1 CNH2
pH 7.0, 30 o
R2 CNH2
O
1a-j
R2 COR3
O
2a-j
of 1e, afforded (ꢀ)-2d with only 42.5% ee (entry 6, Table 1),
reflecting the effect of isomerism on the enantioselectivity. Ex-
cept
a-benzyl-a-(prop-2-ynyl)-malonamide 1j, which gave 85%
Scheme 1. Biotransformation of malonamides 1.
ee of the product (entry 12, Table 1), diamides bearing both an
allyl and a prop-2-ynyl (1h) or a but-2-ynyl (1i) underwent less
enantioselective desymmetrization hydrolysis to form (ꢀ)-2h and
(þ)-2i with low ee values (entries 10 and 11, Table 1). The out-
comes indicated clearly that the larger the steric difference be-
tween substitutes R1 and R2, the higher the enantioselectivity.
Besides, the presence of a carbonecarbon triple bond leads
a dramatic decrease of enantioselectivity. The beneficial effect of
the carbonecarbon double bond of the substrates on the catalytic
efficiency and enantioselectivity of biotransformations of amides
has also been observed previously.6d,6e
Table 1
Biocatalytic desymmetrization of malonamides 1a
Entry
1
R1
R2
R3
t (h)
0.5
2 (%)b (ee %)c
1
1a
1a
1a
1b
1c
1d
1e
1f
Me
Me
Me
Me
Me
Me
Me
Me
Me
allyl
allyl
Bn
allyl
allyl
allyl
Bn
Bn
Bn
Bn
Me
Bn
Bn
Bn
Bn
Bn
Bn
Bn
Me
(ꢀ)-2a (85) (90.7)
(ꢀ)-2a (76) (93.8)
(ꢀ)-2a (59) (95.0)
(þ)-2b (99) (>99.5)
(ꢀ)-2c (80) (72.4)
(ꢀ)-2d (85) (42.5)
(ꢀ)-2e (87) (97.8)
(þ)-2f (73) (43.8)
(ꢀ)-2g (84) (>99.5)
(ꢀ)-2h (88) (41.2)
(þ)-2i (86) (25.2)
(ꢀ)-2j (<5) (85.0)
2d
3e
4
0.67
1.5
8
5
6
7
8
n-Pr
5
2-Methylallyl
E-But-2-enyl
Prop-2-ynyl
Cinnamyl
Prop-2-ynyl
But-2-ynyl
Prop-2-ynyl
0.7
1.3
To examine the practical utility of biocatalytic desymmetriza-
tion, a large scale biotransformation of 1a was tested using an
immobilized Rh. erythropolis AJ270 whole cell catalyst.12 To our
delight, the immobilized biocatalyst was recycled for five times
without noticeable decay of the activity and enantioselectivity,
producing 8 g of (ꢀ)-2a with ee of 88.6%.
25
115
31.5
9
1g
1h
1i
10
11
12f
104.5
168
1j
a
Substrate 1 (1 mmol) was incubated with Rh. erythropolis AJ270 whole cell
The highly enantiopure carbamoylacetates bearing carbone
carbon unsaturated functional groups are valuable chiral interm-
ediates in organic synthesis. To demonstrate their synthetic
applications, and also to determine their absolute configurations,
catalyst (2 g wet weight) in phosphate buffer (pH 7.0, 0.1 M, 50 mL) at 30 ꢁC.
b
Isolated yield.
c
Determined using chiral HPLC.
d
Incubation temperature was 20 ꢁC.
e
Incubation temperature was 10 ꢁC.
both (ꢀ)-2a and (ꢀ)-2g were converted into
a,a-disubstituted
f
Starting material 1j (83%) was recovered.
amino acids 3 and 4 through facile Hofmann rearrangement and
hydrolysis (Scheme 2). The absolute configurations of S-3 and S-4,
that was determined by comparing their optical rotations with that
of authentic samples,13,14 revealed pro-R-enantioselectivity of the
amidase involved in Rh. erythropolis AJ270.
Encouraged by the enantioselective desymmetrization of 1a,
a number of functionalized prochiral malonamides 1bej were
synthesized and their biocatalytic transformation was investigated
(Scheme 1). Results tabulated in Table 1 show that most of the
prochiral diamides underwent effective biocatalytic hydrolysis
under mild conditions to produce carbamoylacetic acid products 2
in good to excellent yields. The reaction velocity and ee values of
the products, however, were dependent dramatically upon the
nature of substituents R1 and R2. The steric effect of the substituents
R1 and R2 played an important role in determining reaction speed.
For example, desymmetrization of malonamides containing one
a
-methyl group and one a-allyl (1a), benzyl (1b), n-propyl (1c),
Scheme 2. Synthesis of amino acids 3 and 4.
2-methylallyl (1d), or E-but-2-enyl (1e) took place efficiently to
afford the corresponding carbamoylacetic acid products in good to
excellent yield yields within hours (entries 1e7, Table 1). In-
Having had a large amount of highly enantioenriched
-methylcarbamoylacetate R-(ꢀ)-2a in hand, our interest in un-
usual amino acids led us to investigate its conversions to other
-disubstituted amino acids that are the useful building blocks
a-allyl-
a
troduction of an
a-prop-2-ynyl (1f), cinnamyl (1g) group in addi-
tion to an -methyl led to a slower reaction rate, yielding products
a
a,a
(þ)-2f and (ꢀ)-2g in 73% and 84% after 25 and 115 h incubation,
respectively (entries 8 and 9, Table 1). When both R1 and R2 were
larger substituents, the reaction became very sluggish. This has
been exemplified by the reaction of
mide 1i, which took more than 100 h to give product (þ)-2i in 86%
(entry 11). An extreme example was the reaction of -benzyl-a-
(prop-2-ynyl)malonamide 1j, which yielded a very small amount of
the product (ꢀ)-2j after a week’s interaction with biocatalyst (entry
12, Table 1).
In contrast to reaction efficiency, the enantioselectivity of
biocatalytic desymmetrization of 1 was dictated predominantly
by the electronic effect of the substituents, and the combination
of substituents R1 and R2. In the case of malonamides 1aeg
in medicinal chemistry.15ꢀ17 Illustrated in Scheme 3 are the
synthesis of S-2-amino-2-methyl-7-phenylheptanoic acid 6 and
S-2-amino-2-methylhexanedioic acid 10. Cross metathesis be-
tween R-(ꢀ)-2a and 4-phenyl-but-1-ene in the presence of
Grubbs II catalyst afforded a mixture of E- and Z-configured al-
kenes 5 in 50%. Hydrogenation reaction followed by typical
Hofmann rearrangement produced compound 6. Similar cross
metathesis of R-(ꢀ)-2a with ethyl acrylate led to the formation of
intermediate 7 in 65% yield. Catalytic hydrogenation, Hofmann
rearrangement using Hg(OAc)2 and NBS, and final hydrolysis
under acidic conditions furnished the formation of product 10
(Scheme 3).
a-allyl-a-(but-2-ynyl)malona-
a

5606
L.-B. Zhang et al. / Tetrahedron 67 (2011) 5604e5609
19.7; MS (ESI) m/z (%) 179 [MþNa]þ (100). Anal. Calcd for C7H12N2O2:
Ph
Ph
Ph
Grubbs II
50%
C, 53.83; H, 7.74; N, 17.94. Found: C, 53.76; H, 7.67; N, 17.72.
1. H2, Pd/C
2. Br2/NaOH
4.2.2. 2-Benzyl-2-methylmalonamide 1b. Mp 211.0e212.0 ꢁC (lit.3
mp 195.4e196.4 ꢁC); 1H NMR (300 MHz, DMSO-d6) 7.26e7.16 (m,
7H), 7.11 (s, 2H), 3.07 (s, 2H), 1.11 (s, 3H).
R-(-)-2a
51%
H2NOC CO2Bn
5
CO2Et
H2N CO2H
6
4.2.3. 2-Methyl-2-propylmalonamide 1c. Mp 179e180 ꢁC (lit.18 mp
182 ꢁC); 1H NMR (300 MHz, DMSO-d6) 7.15 (s, 2H), 7.03 (s, 2H),
1.70e1.65 (m, 2H), 1.21e1.12 (m, 5H), 0.85 (t, J¼7.2 Hz, 3H).
65%
Grubbs II
CO2Et
CO2Et
4.2.4. 2-Methyl-2-(2-methylallyl)malonamide 1d. Mp 158.0e159.0 ꢁC;
IR (KBr) n
3382, 3217, 1641 cmꢀ1; 1H NMR (300 MHz, DMSO-d6) 7.25
1. H2, Pd/C
2. BnBr/K2CO3
(s, 2H), 7.13 (s, 2H), 4.67 (s, 1H), 4.46 (s, 1H), 2.52 (s, 2H), 1.62 (s, 3H),
1.19 (s, 3H); 13C NMR (75 MHz, DMSO-d6) 174.7, 142.0, 114.1, 51.9, 44.2,
23.0, 19.8; MS (ESI) m/z (%) 209 [MþK]þ (13), 193 [MþNa]þ (100), 171
[MþH]þ (65). HRMS for C8H14N2O2: 170.1055 [M]þ. Found: 170.1057
[M]þ.
80%
H2NOC CO2Bn
H2NOC CO2Bn
8
7
CO2Et
HCl/H2O
CO2H
Hg(OAc)2
NBS
4.2.5. (E)-2-(But-2-en-1-yl)-2-methylmalonamide 1e. Mp 169.0e170.0 ꢁC;
IR (KBr) n
3383, 3225, 1692, 1642 cmꢀ1; 1H NMR (300 MHz, DMSO-d6) 7.10
67%
(s, 2H), 7.05 (s, 2H) 5.48e5.41 (m,1H), 5.26e5.21 (m,1H), 2.40 (d, J¼6.3 Hz,
2H), 1.60 (d, J¼5.4 Hz, 3H), 1.16 (s, 3H); 13C NMR (75 MHz, DMSO-d6) 174.2,
127.7, 126.8, 52.7, 19.7, 17.9, 12.9; MS (ESI) m/z (%) 209 [MþK]þ (5), 193
[MþNa]þ (100), 171 [MþH]þ (9). Anal. Calcd for C8H14N2O2: C, 56.45; H,
8.29; N, 16.46. Found: C, 56.12; H, 8.16; N, 16.32.
84%
MeO2CHN CO2Bn
9
H2N CO2H
10
Scheme 3. Synthesis of amino acids 6 and 10.
4.2.6. 2-Methyl-2-(prop-2-yn-1-yl)malonamide1f. Mp 169.0e170.0 ꢁC;
IR (KBr) n
3385, 3275, 1693, 1639 cmꢀ1; 1H NMR (300 MHz, DMSO-d6)
7.12 (s, 4H), 2.79 (t, J¼2.4 Hz, 1H), 2.64 (d, J¼2.4 Hz, 2H), 1.35 (s, 3H); 13C
NMR (75 MHz, DMSO-d6) 172.9, 81.4, 72.9, 52.4, 25.9, 19.9; MS (ESI) m/z
(%) 193 [MþK]þ (6), 177 [MþNa]þ (100), 155 [MþH]þ (13). Anal. Calcd
for C7H10N2O2: C, 54.54; H, 6.54; N, 18.17. Found: C, 54.43; H, 6.53; N,
18.25.
3. Conclusion
In summary, we have shown that Rh. erythropolis AJ270, an
amidase-containing microbial cell catalyst, is able to catalyze the
enantioselective hydrolysis of a,a-disubstituted malonamides un-
der very mild conditions to afford high yield of carbamoylacetic
acid products. Both the catalytic efficiency and enantioselectivity of
4.2.7. 2-Cinnamyl-2-methylmalonamide 1g. Mp 174.0e175.0 ꢁC; IR
(KBr)
n ;
3409, 3197, 1658 cmꢀ1 1H NMR (300 MHz, DMSO-d6)
desymmetrization of
a,a-disubstituted malonamides were de-
7.36e7.28 (m, 4H), 7.23e7.20 (m, 3H), 7.15 (s, 2H), 6.44 (d,
J¼15.6 Hz, 1H), 6.14e6.04 (m, 1H), 2,64 (d, J¼7.2 Hz, 2H), 1.26 (s,
3H); 13C NMR (75 MHz, DMSO-d6) 174.1, 137.0, 132.4, 128.5, 127.1,
126.1, 125.8, 53.0, 40.1 19.9; MS (ESI) m/z (%) 271 [MþK]þ (66), 255
[MþNa]þ (100), 233 [MþH]þ (13). Anal. Calcd for C13H16N2O2: C,
67.22; H, 6.94; N, 12.06. Found: C, 67.27; H, 7.01; N, 12.14.
pendent upon the substituents on the substrate. The amidase-
catalyzed enantioselective desymmetrization reaction provided
an efficient and practical method for the preparation of highly
enantiopure functionalized carbamoylacetic acids, and their syn-
thetic applications have been demonstrated in the preparation of
unusual a,a-disubstituted a-amino acids.
4.2.8. 2-Allyl-2-(prop-2-yn-1-yl)malonamide 1h. Mp 169.0e170.0 ꢁC;
IR (KBr) n
3389, 3277, 1642 cmꢀ1; 1H NMR (300 MHz, DMSO-d6) 7.23
4. Experimental section
4.1. General information
(s, 2H), 7.19 (s, 2H) 5.64e5.50 (m, 1H), 5.13e5.04 (m, 2H), 2.79 (t,
J¼2.4 Hz, 1H), 2.66e2.62 (m, 4H); 13C NMR (75 MHz, DMSO-d6) 171.7,
133.5, 118.5, 80.9, 73.0, 55.7, 36.7, 22.1; MS (ESI) m/z (%) 219 [MþK]þ
(66), 203 [MþNa]þ (100), 181 [MþH]þ (13). Anal. Calcd for
C9H12N2O2: C, 59.99; H, 6.71; N, 15.55. Found: C, 59.72; H, 6.70; N,
15.32.
1H and 13C NMR spectra were recorded on a 300 MHz spec-
trometer. Chemical shifts are reported in parts per million versus
tetramethylsilane or the residual solvent resonance used as an in-
ternal standard. Melting points are uncorrected. Enantiomeric ex-
cess values of all compounds were obtained from chiral HPLC
analyses (see Supplementary data). Prochiral diamides 1 were
prepared from the chemical hydrolysis of dinitriles using H2O2
under basic conditions following the literature method.6d,e
4.2.9. 2-Allyl-2-(but-2-yn-1-yl)malonamide 1i. Mp 183.0e184.0 ꢁC;
IR (KBr) n
3409, 3214, 1696, 1654 cmꢀ1; 1H NMR (300 MHz, DMSO-
d6) 7.19 (s, 2H), 7.12 (s, 2H) 5.61e5.52 (m, 1H), 5.12e5.01 (m, 2H),
2.63e2.57 (m, 4H), 1.71 (s, 3H); 13C NMR (75 MHz, DMSO-d6) 172.2,
133.4, 118.4, 77.6, 75.4, 55.9, 36.9, 22.7, 3.1; MS (ESI) m/z (%) 217
[MþNa]þ (100), 195 [MþH]þ (13). Anal. Calcd for C10H14N2O2: C,
61.84; H, 7.27; N, 14.42. Found: C, 61.92; H, 7.37; N, 14.52.
4.2. Spectroscopic data of diamides 1
4.2.10. 2-Benzyl-2-(prop-2-yn-1-yl)malonamide1j. Mp 211.0e212.0 ꢁC;
4.2.1. 2-Allyl-2-methylmalonamide 1a. Mp 163.0e164.0 ꢁC; IR (KBr)
IR (KBr) n
3380, 3293, 3208, 1644 cmꢀ1; 1H NMR (300 MHz, DMSO-d6)
n
3382,1643 cmꢀ1; 1H NMR (300 MHz, DMSO-d6) 7.13 (s, 2H), 7.01 (s,
7.34 (s, 2H), 7.18e7.23 (m, 7H), 3.21 (s, 2H), 2.94 (s, 1H), 2.50 (s, 2H); 13C
NMR (75 MHz, DMSO-d6) 171.7, 137.0, 129.7, 127.9, 126.5, 81.3, 73.6, 57.2,
37.7, 22.1; MS (ESI) m/z (%) 269 [MþK]þ (2), 253 [MþNa]þ (100), 231
2H), 5.68e5.54 (m,1H), 5.08e5.01 (m, 2H), 2,47 (d, J¼7.2 Hz, 2H),1.18
(s, 3H); 13C NMR (75 MHz, DMSO-d6) 174.0, 134.5, 117.9, 52.5, 40.9,

L.-B. Zhang et al. / Tetrahedron 67 (2011) 5604e5609
5607
[MþH]þ (48). Anal. Calcd for C13H14N2O2: C, 67.81; H, 6.13; N, 12.17.
Anal. Calcd for C15H19NO3: C, 68.94; H, 7.33; N, 5.36. Found: C,
68.82; H, 7.41; N, 5.32.
Found: C, 67.51; H, 6.14; N, 12.31.
4.3. General procedure for the biotransformation of
bstituted malonamides 1
a
,
a-disu-
4.3.5. (ꢀ)-(E)-Benzyl 2-carbamoyl-2-methylhex-4-enoate (2e). Mp
25
56.5e57.0 ꢁC; [
a]
ꢀ21.9 (c 0.85, CHCl3); ee¼97.8% (chiral HPLC
D
analysis); IR (KBr)
n ;
3424, 3183, 1622 cmꢀ1 1H NMR (300 MHz,
To an Erlenmeyer flask (150 mL) with a screw cap were added
Rh. erythropolis AJ270 cells4,19 (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. A solution of
prochiral diamides 1 (1 mmol) or a solution of diamides 1c and 1g
(1 mmol) in DMF (1 mL) 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 GC, was quenched
after a specified period of time (Table 1) by removing the biomass
through a Celite pad filtration. The aqueous solution was freeze-
dried, and the residue was dissolved in DMF (5 mL) and then
treated with K2CO3 (270 mg, 2 mmol) and benzyl bromide (0.13 mL,
1.05 mmol) or methyl iodide (0.3 mL, 5 mmol). The mixture was
kept stirring at room temperature overnight, and water (25 mL)
was added and the mixture was extracted with ethyl acetate
(3ꢂ25 mL). For the biotransformation of 1b, the residue was dis-
solved in methanol (10 mL) followed by adding a solution of CH2N2
in ethyl ether at below 0 ꢁC. After 4e6 h, water was added and the
mixture was extracted with ethyl acetate (3ꢂ25 mL). Organic phase
was dried over MgSO4. After removal of the solvent under vacuum,
the residue was chromatographed on a silica gel column with
a mixture of petroleum ether and ethyl acetate (3:1) as the mobile
phase to give products 2.
CDCl3) 7.35e7.33 (m, 5H), 6.64 (s, 1H), 5.62 (s, 1H), 5.61e5.42 (m,
1H), 5.31e5.24 (m, 1H), 5.23 (d, J¼3 Hz, 2H), 2.67e2.61 (m, 1H),
2.52e2.45 (m, 1H), 1.61 (d, J¼3 Hz, 3H), 1.43 (s, 3H); 13C NMR
(75 MHz, DMSO-d6) 174.0, 173.4, 135.4, 130.1, 128.6, 128.4, 128.2,
124.9, 67.2, 54.0, 41.0, 20.4, 18.0; MS (ESI) m/z (%) 284 [MþNa]þ
(100), 262 [MþH]þ (9). Anal. Calcd for C15H19NO3: C, 68.94; H, 7.33;
N, 5.36. Found: C, 68.56; H, 7.23; N, 5.34.
4.3.6. (þ)-Benzyl 2-carbamoyl-2-methylpent-4-ynoate (2f). Mp
25
48.0e49.0 ꢁC; [
a
]
D
þ27.2 (c 0.5, CHCl3); ee¼43.8% (chiral HPLC
analysis); IR (KBr)
n ;
3451, 3290, 1726, 1691 cmꢀ1 1H NMR
(300 MHz, CDCl3) 7.37 (s, 5H), 6.49 (s, 1H), 6.16 (s, 1H), 5.22 (s, 2H),
2.89 (dd, J¼16.8, 2.4 Hz, 1H), 2.76 (dd, J¼16.8, 2.4 Hz, 1H) 2.04 (t,
J¼2.4 Hz, 1H), 1.59 (s, 3H); 13C NMR (75 MHz, CDCl3) 172.5, 172.4,
135.1, 128.6, 128.5, 128.1, 79.8, 71.4, 67.7, 53.4, 26.3, 21.1; MS (ESI) m/
z (%) 284 [MþK]þ (3), 268 [MþNa]þ (100). Anal. Calcd for
C14H15NO3: C, 68.56; H, 6.16; N, 5.71. Found: C, 68.49; H, 6.15; N,
5.73.
4.3.7. R-(ꢀ)-(E)-Benzyl 2-carbamoyl-2-methyl-5-phenylpent-4-
25
enoate (2g). Mp 60.5e61.0 ꢁC; [
a
]
D
ꢀ29.6 (c 0.5, CHCl3); ee
>99.5% (chiral HPLC analysis); IR (KBr)
n 3411, 3197, 1722,
1665 cmꢀ1 1H NMR (300 MHz, CDCl3) 7.37 (s, 5H), 7.30e7.25 (m,
;
5H), 6.81 (s, 1H), 6.42 (d, J¼15.7 Hz, 1H), 6.08e5.98 (m, 1H), 5.93 (s,
1H), 5.25 (d, J¼12.3 Hz, 1H), 5.19 (d, J¼12.3 Hz, 1H), 2.91 (dd, J¼13.7,
7.2 Hz, 1H), 2.74 (dd, J¼13.7, 7.2 Hz, 1H), 1.53 (s, 3H); 13C NMR
(75 MHz, CDCl3) 173.9, 173.4, 137.0, 135.3, 134.2, 128.7, 128.52,
128.49, 128.3, 127.5, 126.3, 124.1, 67.4, 54.2, 41.1, 21.0; MS (ESI) m/z
(%) 362 [MþK]þ (4), 346 [MþNa]þ, 324 [MþH]þ (19). Anal. Calcd for
C20H21NO3: C, 74.28; H, 6.55; N, 4.33. Found: C, 74.28; H, 6.54; N,
4.48.
4.3.1. R-(ꢀ)-Benzyl 2-carbamyl-2-methylpent-4-enoate (2a). Mp
25
25.0e25.5 ꢁC; [
a
]
ꢀ14.5 (c 0.8, CHCl3); ee¼90.7% (chiral HPLC
D
analysis); IR (KBr)
n
3419, 3191,1727, 1678 cmꢀ1; 1H NMR (300 MHz,
CDCl3) 7.37e7.28 (m, 5H), 6.67 (s, 1H), 5.96 (s, 1H), 5.75e5.61 (m,
1H), 5.19 (s, 2H), 5.11e5.06 (m, 2H), 2.73 (dd, J¼13.7, 7.2 Hz, 1H),
2.58 (dd, J¼13.7, 7.2 Hz, 1H), 1.47 (s, 3H); 13C NMR (75 MHz, CDCl3)
173.7, 173.4, 135.2, 132.6, 128.6, 128.5, 128.2, 119.3, 67.3, 53.7, 41.9,
20.6; MS (ESI) m/z (%) 270 [MþNa]þ (100), 248 [MþH]þ (6). Anal.
Calcd for C14H17NO3: C, 68.00; H, 6.93; N, 5.66. Found: C, 68.09; H,
6.96; N, 5.78.
4.3.8. (ꢀ)-Benzyl 2-carbamoyl-2-(prop-2-yn-1-yl)pent-4-enoate
25
(2h). Mp 35.5e36.0 ꢁC; [
HPLC analysis); IR (KBr)
a
n
]
ꢀ8.5 (c 0.4, CHCl3); ee¼41.2% (chiral
D
3414, 3299, 1725, 1669 cmꢀ1 1H NMR
;
4.3.2. R-(þ)-Methyl 3-amino-2-benzyl-2-methyl-3-oxopropanoate
(300 MHz, CDCl3) 7.40e7.38 (m, 5H), 6.96 (s, 1H), 5.86 (s, 1H),
5.71e5.57 (m, 1H), 5.23 (s, 2H), 5.16e5.10 (m, 2H), 2.94e2,65 (m,
4H), 2.04 (t, J¼2.4 Hz, 1H); 13C NMR (75 MHz, DMSO-d6) 171.9, 171.1,
135.0, 131.5, 128.61, 128.56, 128.4, 120.0, 79.6, 71.4, 67.7, 57.3, 39.6,
24.1; MS (ESI) m/z (%) 310 [MþK]þ (3), 294 [MþNa]þ (100), 272
[MþH]þ (3). Anal. Calcd for C16H17NO3: C, 70.83; H, 6.32; N, 5.16.
Found: C, 70.93; H, 6.34; N, 5.00.
25
(2b). Mp 111.0e112.0 ꢁC (lit.20 mp 104e106 ꢁC); [
a]
þ25 (c 2,
D
20
CHCl3); {lit.20
[
a
]
þ9.8 (c 0.5, CHCl3)}; ee >99.5% (chiral HPLC
D
analysis); 1H NMR (300 MHz, CDCl3) 7.28e7.22 (m, 3H), 7.14e7.11
(m, 2H), 6.89 (s,1H), 5.54 (s,1H), 3.73 (s, 3H), 3.36 (d, J¼13.2 Hz,1H),
3.11 (d, J¼13.2 Hz, 1H), 1.44 (s, 3H).
4.3.3. (ꢀ)-Benzyl
2-carbamoyl-2-methylpentanoate
(2c). Mp
25
D
n
61.0e61.5 ꢁC; [
analysis); IR (KBr)
a
]
ꢀ28.0 (c 0.5, CHCl3); ee¼72.4% (chiral HPLC
4.3.9. (þ)-Benzyl
67.5e38.5 ꢁC; [
analysis); IR (KBr)
(300 MHz, CDCl3) 7.36e7.34 (m, 5H), 6.95 (s, 1H), 5.91 (s, 1H),
5.71e5.57 (m, 1H), 5.2 (s, 2H), 5.20e5.05 (m, 2H), 2.85e2,61 (m,
4H), 1.70 (s, 3H); 13C NMR (75 MHz, DMSO-d6) 172.2, 171.6, 135.3,
132.0, 128.5, 128.4, 128.2, 119.5, 79.0, 74.1, 67.4, 57.7, 39.4, 24.9, 3.5;
MS (ESI) m/z (%) 324 [MþK]þ (3), 308 [MþNa]þ (100), 286 [MþH]þ
(6). Anal. Calcd for C17H19NO3: C, 71.56; H, 6.71; N, 4.91. Found: C,
71.37; H, 6.73; N, 4.81.
2-allyl-2-carbamoylhex-4-ynoate
(2i). Mp
þ5.6 (c 0.5, CHCl3); ee¼25.2% (chiral HPLC
3415, 3206, 1728, 1672 cmꢀ1 1H NMR
25
3418, 3187, 1716, 1686 cmꢀ1; 1H NMR (300 MHz,
a]
D
CDCl3) 7.39e7.37 (m, 5H), 6.87 (s, 1H), 5.58 (s, 1H), 5.20 (s, 2H),
1.97e1.79 (m, 2H), 1.48 (s, 3H), 1.26e1.24 (m, 2H), 0.90 (t, J¼6.6 Hz,
3H); 13C NMR (75 MHz, CDCl3) 174.6, 173.9, 135.4, 128.6, 128.4,
128.0, 67.1, 53.9, 40.3, 20.7, 18.3, 14.2; MS (ESI) m/z (%) 272 [MþNa]þ
(100), 250 [MþH]þ (5). Anal. Calcd for C14H19NO3: C, 67.45; H, 7.68;
N, 5.62. Found: C, 67.33; H, 7.64; N, 5.61.
n
;
4.3.4. (ꢀ)-Benzyl 2-carbamoyl-2,4-dimethylpent-4-enoate (2d). Mp
25
49.0e49.5 ꢁC; [
a
]
ꢀ6.8 (c 0.5, CHCl3); ee¼42.5% (chiral HPLC
D
analysis); IR (KBr)
n
3408, 3195, 1713, 1662 cmꢀ1
;
1H NMR
4.3.10. (ꢀ)-Methyl 2-benzyl-2-carbamoylpent-4-ynoate (2j). Mp
25
(300 MHz, CDCl3) 7.41e7.36 (m, 5H), 7.17 (s, 1H), 6.14 (s, 1H), 5.17 (s,
2H), 4.81(s, 1H), 4.67 (s, 1H), 2.85 (d, J¼14.4 Hz, 1H), 2.56 (d,
J¼14.4 Hz, 1H), 1.66 (s, 3H), 1.48 (s, 3H); 13C NMR (75 MHz, DMSO-
d6) 174.6,174.0,141.2,135.1,128.6,128.5,128.2,114.5, 67.4, 53.0, 45.1,
23.3, 21.8; MS (ESI) m/z (%) 284 [MþNa]þ (100), 262 [MþH]þ (18).
108.5e109.5 ꢁC; [
a
]
ꢀ2.7 (c 0.6, CHCl3); ee¼85% (chiral HPLC
D
analysis); IR (KBr)
n ;
3398, 3290, 1731, 1672 cmꢀ1 1H NMR
(300 MHz, CDCl3) 7.30e7.14 (m, 6H), 6.02 (s, 1H), 3.80 (s, 3H), 3.40
(d, J¼13.4 Hz, 1H), 3.22 (d, J¼13.4 Hz, 1H), 2.90 (dd, J¼16.7, 2.4 Hz,
1H), 2.72 (dd, J¼16.7, 2.4 Hz, 1H), 2.12 (t, J¼2.4 Hz, 1H); 13C NMR

5608
L.-B. Zhang et al. / Tetrahedron 67 (2011) 5604e5609
(75 MHz, DMSO-d6) 171.5,170.3,134.5,128.7,127.4,126.3, 78.8, 70.6,
58.1, 51.7, 40.2, 23.6; MS (ESI) m/z (%) 246 [MþH]þ (100). Anal. Calcd
for C14H15NO3: C, 68.56; H, 6.16; N, 5.71. Found: C, 68.45; H, 6.27; N,
5.80.
[MþK]þ (8). HRMS for C22H25NO3: 352.1907 [Mþ1]þ. Found:
352.1904 [Mþ1]þ.
4.7. Synthesis of 6
In the presence of Pd/C (10%, 12 mg), compound 5 (100 mg,
0.3 mmol) in methanol (10 mL) was hydrogenated using a hydrogen
balloon. When the starting material was consumed, the catalyst
was filtered and the filtrate was concentrated. The residue was
mixed with aqueous NaOH (2 N, 4 mL), and liquid bromine
(0.05 mL) was added at 0 ꢁC. Following the procedure for the
synthesis of 3 and 4, (S)-2-amino-2-methyl-7-phenylheptanoic
acid 6 (36 mg, 51%) was obtained from chromatography of a re-
versed phase column packed with SP-120-50-ODS-A using a mix-
4.4. General procedure for a large scale biotransformation of
1a using an immobilized whole cell catalyst
The immobilized Rh. erythropolis AJ270 cells (4 g wet weight) in
alginate capsules12 were activated in sodium bicarbonate buffer
solution (pH 7.25, 100 mL) at 30 ꢁC for 30 min. A solution of 1a
(1.5 g, 10 mmol) in bicarbonate buffer solution (pH 7.25, 50 mL) was
added. The resulting mixture was incubated at 30 ꢁC with orbital
shaking for 80 min. The immobilized catalyst was filtered and
reused for another four times. The combined aqueous solution was
worked up and (ꢀ)-2a (8 g, 65% yield, 88.6% ee) was obtained.
ture of water and methanol as mobile phase. Compound 6: 235 ꢁC
25
(sublimation); [
a]
þ3.6 (c 2.8, MeOH); IR (KBr)
n 3439, 1732,
D
1588 cmꢀ1
;
1H NMR (300 MHz, MeOD) 7.27e7.04 (m, 5H), 2.54 (t,
J¼7.5 Hz, 2H), 1.89e1.69 (m, 2H), 1.89e1.69 (m, 2H), 1.48 (s, 3H),
1.44e1.22 (m, 4H); 13C NMR (75 MHz, MeOD) 173.8, 143.6, 129.4,
129.3, 126.8, 61.0, 38.4, 36.6, 32.3, 29.9, 24.4, 22.9; MS (ESI) m/z (%)
234 [Mꢀ1]þ (100). HRMS for C22H25NO3: 236.1645 [Mþ1]þ. Found:
236.1645 [Mþ1]þ.
4.5. Synthesis of amino acids S-(L)-3 and S-(L)-4
A mixture of R-(ꢀ)-2a or R-(ꢀ)-2g (1 mmol) in an aqueous NaOH
solution (2N, 10 mL) was stirred at room temperature until the
completion of hydrolysis of ester. The mixture was then cooled
down to 0 ꢁC, and liquid bromine (0.13 mL, 2.5 mmol) was added.
After 0.5 h, the mixture was warmed to 75 ꢁC, and kept stirring for
4 h. The reaction mixture was then neutralized with hydrochloric
acid. For the reaction of R-(ꢀ)-2g, white precipitate was formed and
filtrated. Recrystallization in methanol gave pure S(ꢀ)-4 (106 mg,
51%). For the reaction of R-(ꢀ)-2a, solvent was removed under
vacuum and the residue was chromatographed on a column packed
with reversed phase materials SP-120-50-ODS-A with water as
mobile phase to give pure amino acid S-(ꢀ)-3 (38 mg, 30%).
4.8. Synthesis of 7
Following the same procedure for the preparation of 5, (R,E)-6-
benzyl 1-ethyl 5-carbamoyl-5-methylhex-2-enedioate 7 (206 mg,
65%) was obtained from the reaction between R-(ꢀ)-2a (247 mg,
1 mmol) and ethyl acrylate (0.54 mL, 5 mmol). Compound 7: oil.
[a
]
25 ꢀ3.0 (c 1.4, CHCl3); IR (KBr)
n
3445, 3350, 1725 cmꢀ1; 1H NMR
D
(300 MHz, CDCl3) 7.31e7.27 (m, 5H), 6.76 (m, 1H), 6.54 (s, 1H), 5.91
(s, 1H), 5.76 (d, J¼15.3 Hz, 1H), 5.11 (s, 2H), 4.08 (q, J¼7.2 Hz, 2H),
2.82e2.60 (m, 2H), 1.40 (s, 3H), 1.19 (t, J¼7.2 Hz, 3H); 13C NMR
(75 MHz, CDCl3) 173.1, 172.6, 165.9, 142.7, 135.0, 128.7, 128.6, 128.2,
125.2, 67.7, 60.4, 53.3, 39.3, 21.4, 14.2; MS (ESI) m/z (%) 342
[MþNa]þ (100), 320 [MþH]þ (63). HRMS for C17H21NO5: 320.1492
[Mþ1]þ. Found: 320.1488 [Mþ1]þ.
4.5.1. S-(ꢀ)-2-Amino-2-methylpent-4-enoic acid (S-(ꢀ)-3). 245 ꢁC
25
(sublimation) (lit.14 mp 308 ꢁC); [
a
]
D
25 ꢀ24.6 (c 1.3, H2O); {lit.14
[a]
D
ꢀ28.5 (c 1.3, H2O)}; IR (KBr)
n
, 3525, 3383,1644,1572 cmꢀ1; 1H NMR
(300 MHz, D2O) 5.76e5.62 (m, 1H), 5.22e5.17 (m, 2H), 2.60 (dd,
J¼13.7, 7.2 Hz, 1H), 2.38 (dd, J¼13.7, 7.2 Hz, 1H), 1.41 (d, J¼1.5 Hz,
3H); 13C NMR (75 MHz, D2O) 176.4, 130.7, 121.3, 60.9, 41.4, 22.0.
Anal. Calcd for C6H11NO2: C, 55.80; H, 8.58; N, 10.84. Found: C,
55.45; H, 8.70; N, 10.66.
4.9. Synthesis of 10
In the presence of Pd/C (10%, 24 mg), compound 7 (200 mg,
0.6 mmol) in methanol (10 mL) was hydrogenated using a hydrogen
balloon. When the starting material was consumed, the catalyst was
filtered and the filtrate was concentrated. The residue was mixed
with K2CO3 (300 mg, 2.2 mmol) and benzyl bromide (0.2 mL,
1.5 mmol) in acetone (10 mL). After stirring at room temperature for
12 h, the solvent was removed under vacuum, The residue was
chromatographed on a silica gel column using a mixture of petro-
leum ether and ethyl acetate (1:3) as the mobile phase to give (R)-1-
benzyl 6-ethyl 2-carbamoyl-2-methylhexanedioate 8 (158 mg, 78%):
4.5.2. S-(ꢀ)-(E)-2-Amino-2-methyl-5-phenylpent-4-enoic acid (S-
(ꢀ)-4). Mp 249e250 ꢁC (lit.14 mp 249e250 ꢁC); [
a
]
25 ꢀ12.5 (c 1.0,
D
25
MeOH); {lit.14
[
a
]
ꢀ12.9 (c 0.51, MeOH)}; IR (KBr)
n 3368, 1673,
D
1585 cmꢀ1; 1H NMR (300 MHz, MeOD) 7.40 (d, J¼7.5 Hz, 2H), 7.31 (t,
J¼7.5 Hz, 2H), 7.21 (t, J¼7.5 Hz, 1H), 6.48 (d, J¼15.9 Hz, 1H),
6.29e9.16 (m, 1H), 2.82e2.66 (m, 2H), 1.35 (s, 3H); 13C NMR
(75 MHz, acetone) 179.7, 138.6, 133.2, 129.4, 128.1, 127.8, 126.9, 56.2,
24.2, 21.6; MS (ESI) m/z (%) 204 [Mꢀ1]þ (76).
oil. [
a
]
25 ꢀ6.7 (c 0.9, CHCl3); ee¼85% (chiral HPLC analysis); IR (KBr)
n
D
4.6. Synthesis of 5
3449, 3356, 1734, 1600 cmꢀ1; 1H NMR (300 MHz, CDCl3) 7.32e7.23
(m, 5H), 6.83 (s, 1H), 5.89 (s, 1H), 5.11 (s, 2H), 4.03 (q, J¼7.2 Hz, 2H),
2.23e2.17 (m, 2H), 1.94e1.75 (m, 2H), 1.54e1.46 (m, 2H), 1.40 (s, 3H),
1.16 (t, J¼7.2 Hz, 3H); 13C NMR (75 MHz, CDCl3) 174.0, 173.8, 173.1,
135.3, 128.6, 128.4, 128.1, 67.3, 60.4, 53.7, 36.8, 34.0, 20.9, 20.3, 14.2;
MS (ESI) m/z (%) 344 [MþNa]þ (33), 322 [MþH]þ (100). HRMS for
C17H23NO5: 322.1649 [Mþ1]þ. Found: 322.1640 [Mþ1]þ.
To a solution of R-(ꢀ)-2a (247 mg, 1 mmol) and 4-phenyl-but-1-
ene (0.75 mL, 5 mmol) in dry toluene (10 mL) under argon pro-
tection was added through a syringe a solution of Grubbs II catalyst
(40 mg, 5 mmol %) in dry toluene (5 mL). The resulting mixture was
refluxed until R-(ꢀ)-2a was consumed. After reaction was
quenched by adding water (0.5 mL), and removal of solvent under
vacuum, the residue was chromatographed on a silica gel column
using a mixture of petroleum ether, ethyl acetate, and 1,4-dioxane
(15:5:1) as the mobile phase to give (R)-benzyl 2-carbamoyl-2-
To a mixture of NBS (73 mg, 0.45 mmol) and Hg(OAc)2 (134 mg,
0.42 mmol) in dry methanol (540 mL, 10 mmol) under argon pro-
tection was added a solution of 9 (100 mg, 0.35 mmol) in dry DMF
(4 mL) through a syringe. The resulting mixture was stirred at room
temperature overnight. Water (20 mL) was added and the mixture
was extracted with ethyl acetate (3ꢂ25 mL). After drying with MgSO4
and removal of the solvent, the residue was chromatographed on
a silica gel column using a mixture of petroleum ether and ethyl
methyl-7-phenylhept-4-enoate 5 (176 mg, 50%): oil. IR (KBr)
n
3455, 3355, 1731, 1678 cmꢀ1 13C NMR (75 MHz, CDCl3) 173.8, 173.6,
;
141.7, 140.3, 135.3, 134.6, 128.6, 128.4, 128.3, 128.2, 125.8, 124.6, 67.2,
53.9, 40.8, 35.6, 34.1, 20.5; MS (ESI) m/z (%) 374 [MþNa]þ (100), 390

L.-B. Zhang et al. / Tetrahedron 67 (2011) 5604e5609
5609
3. (a) Wu, Z.-L.; Li, Z.-Y. J. Org. Chem. 2003, 68, 2479; (b) For a related study in-
volving amidase-catalyzed biotransformation, see Yokoyama, M.; Kashiwagi,
M.; Iwasaki, M.; Fuhshuku, K.-i.; Ohta, H.; Sugai, T. Tetrahedron: Asymmetry
2004, 15, 2817.
4. (a) Blakey, A. J.; Colby, J.; Williams, E.; O’Reilly, C. FEMS Microbiol. Lett. 1995, 129,
57; (b) O’Mahony, R.; Doran, J.; Coffey, L.; Cahill, O. J.; Black, G. W.; O’Reilly, C.
Antonie van Leeuwenhoek 2005, 87, 221.
acetate (5:1) as the mobile phase to give methyl (S)-2-((benzyloxy)
carbonyl)-5-(ethoxycarbonyl)pentan-2-ylcarbamate 9 (82 mg, 67%):
190 ꢁC (sublimation); [
analysis); IR (KBr)
a]
D
25 20.0 (c 0.4, CHCl3); ee¼86.8% (chiral HPLC
n
3358, 3299, 1726, 1519 cmꢀ1; 1H NMR (300 MHz,
CDCl3) 7.30e7.25 (m, 5H), 5.57 (s, 1H), 5.13 (s, 2H), 4.03 (q, J¼7.2 Hz,
2H), 3.55 (s, 3H), 2.20e2.05 (m, 2H), 2.02e2.00 (m,1H),1.83e1.73 (m,
1H), 1.83e1.44 (m, 4H), 1.40e1.20 (m, 1H), 1.30 (t, J¼7.5 Hz, 3H); 13C
NMR (75 MHz, CDCl3) 173.9, 173.1, 155.3, 135.5, 128.6, 128.4, 128.2,
67.4, 60.3, 59.7, 51.8, 36.1, 33.8, 23.3, 19.4, 14.2; MS (ESI) m/z (%) 374
[MþNa]þ (100), 352 [MþH]þ (64). HRMS for C18H25NO6: 352.1755
[Mþ1]þ. Found: 352.1748 [Mþ1]þ.
5. For reviews, see: (a) Wang, M.-X. Top. Catal. 2005, 35, 117; (b) Wang, M.-X.
Chimia 2009, 63, 331.
6. For the synthesis of chiral carboxylic acids and amides bearing a functional
group, see: (a) Wang, M.-X.; Zhao, S.-M. Tetrahedron Lett. 2002, 43, 6617; (b)
Wang, M.-X.; Zhao, S.-M. Tetrahedron: Asymmetry 2002, 13, 1695; (c) Ma, D.-Y.;
Wang, D.-X.; Zheng, Q.-Y.; Wang, M.-X. Tetrahedron: Asymmetry 2006, 17, 2366;
(d) Gao, M.; Wang, D.-X.; Zheng, Q.-Y.; Wang, M.-X. J. Org. Chem. 2006, 71, 9532;
(e) Gao, M.; Wang, D.-X.; Zheng, Q.-Y.; Huang, Z.-T.; Wang, M.-X. J. Org. Chem.
2007, 72, 6060.
Compound 9 (56 mg, 0.15 mmol) was refluxed in hydrochloric
acid (20%, 3 mL) for 4 h. After removal of the solvent, the residue
was mixed with water (10 mL) and extracted with ethyl acetate
(3ꢂ10 mL). The aqueous phase was concentrated under vacuum
and then chromatographed on a reversed phase column packed
with SP-120-50-ODS-A using water as mobile phase to give pure
7. For the synthesis of chiral
a- and b-amino and -hydroxy acids and amides, see:
(a) Wang, M.-X.; Lin, S.-J. J. Org. Chem. 2002, 67, 6542; (b) Wang, M.-X.; Wu, Y.
Org. Biomol. Chem. 2003, 1, 535; (c) Wang, M.-X.; Lin, S.-J.; Liu, J.; Zheng, Q.-Y.
Adv. Synth. Catal. 2004, 346, 439; (d) Wang, M.-X.; Liu, J.; Wang, D.-X.; Zheng,
Q.-Y. Tetrahedron: Asymmetry 2005, 16, 2409; (e) Ma, D.-Y.; Zheng, Q.-Y.; Wang,
D.-X.; Wang, M.-X. Org. Lett. 2006, 8, 3231; (f) Ma, D.-Y.; Wang, D.-X.; Pan, J.;
Huang, Z.-T.; Wang, M.-X. Tetrahedron: Asymmetry 2008, 19, 322; (g) Ma, D.-Y.;
Wang, D.-X.; Pan, J.; Huang, Z.-T.; Wang, M.-X. J. Org. Chem. 2008, 73, 4087; (h)
Liu, J.; Wang, D.-X.; Zheng, Q.-Y.; Wang, M.-X. Chem. J. Chem. 2006, 24, 1665.
8. For the synthesis of chiral cyclopropanecarboxylic acids and amides, see: (a)
Wang, M.-X.; Feng, G.-Q. Tetrahedron Lett. 2000, 41, 6501; (b) Wang, M.-X.;
Feng, G.-Q. J. Mol. Catal. B: Enzym. 2002, 18, 267; (c) Wang, M.-X.; Feng, G.-Q.
New J. Chem. 2002, 26, 1575; (d) Wang, M.-X.; Feng, G.-Q. Adv. Synth. Catal.
2003, 345, 695; (e) Wang, M.-X.; Feng, G.-Q. J. Org. Chem. 2003, 68, 621; (f)
Wang, M.-X.; Feng, G.-Q.; Zheng, Q.-Y. Tetrahedron: Asymmetry 2004, 15, 347.
9. For the synthesis of chiral oxiranecarboxamides, see: (a) Wang, M.-X.; Lin, S.-J.;
Liu, C.-S.; Zheng, Q.-Y.; Li, J.-S. J. Org. Chem. 2003, 68, 4570; (b) Wang, M.-X.;
Deng, G.; Wang, D.-X.; Zheng, Q.-Y. J. Org. Chem. 2005, 70, 2439.
10. For the synthesis of chiral aziridinecarboxylic acids and amides, see: (a) Wang,
J.-Y.; Wang, D.-X.; Zheng, Q.-Y.; Huang, Z.-T.; Wang, M.-X. J. Org. Chem. 2007, 72,
2040; (b) Wang, J.-Y.; Wang, D.-X.; Pan, J.; Huang, Z.-T.; Wang, M.-X. J. Org.
Chem. 2007, 72, 9391.
(S)-2-amino-2-methylhexanedioic acid 10 (22 mg, 84%) as white
25
solid: mp 147.0e148.0 ꢁC; [
a]
þ16.0 (c 0.25, MeOH); IR (KBr)
n
D
3422, 3182, 1716, 1591 cmꢀ1 1H NMR (300 MHz, D2O) 2.37 (t,
;
J¼7.2 Hz, 2H), 2.02e1.78 (m, 2H), 1.76e1.58 (m, 1H), 1.56e1.50 (m,
4H); 13C NMR (75 MHz, D2O) 177.5, 174.1, 60.0, 35.9, 33.0, 21.6, 18.5;
MS (ESI) m/z (%) 174 [Mꢀ1]þ (100). HRMS for C7H13NO4: 176.0917
[Mþ1]þ. Found: 176.0920 [Mþ1]þ.
Acknowledgements
We thank the NNSFC (20772132), MOST (2009CB724704,
2009ZX09501), and CAS (KSCXZ-YW-G-051) for financial support.
11. For the synthesis of chiral azetidine- and azetidinone-carboxylic acids and
amides, see: (a) Leng, D.-H.; Wang, D.-X.; Pan, J.; Huang, Z.-T. J. Org. Chem. 2009,
74, 6077; (b) Leng, D.-H.; Wang, D.-X.; Huang, Z.-T. Org. Biomol. Chem. 2010, 8,
4736.
Supplementary data
12. Guo, X.-L.; Deng, G.; Xu, J.; Wang, M.-X. Enzyme Microb. Technol. 2006, 39, 1.
13. Qiu, W.; Soloshonok, V. A.; Cai, C.-Z.; Tang, X.-J.; Hruby, V. J. Tetrahedron 2000,
56, 2577.
14. Yuri, N. B.; Vladimir, I. B.; Nina, I. C.; Konstantin, A. K.; Sergei, V. V.; Natalia, S.
G.; Vasili, M. B. J. Chem. Soc., Perkin Trans. 1 1988, 305.
Chiral HPLC analysis of chiral products. Supplementary data
associated with this article can be found, in the online version, at
doi:10.1016/j.tet.2011.05.103.
15. Christian, E. S.; Julia, P.; Gregory, L. V. J. Am. Chem. Soc. 2000, 122, 5891.
16. Aurash, S.; James, S. K.; Elizabeth, A. L.; Bruce, A. S.; James, M. H.; Harriet, W. H.;
Tomi, K. S.; Christine, H.; Annette, M. D. J. Med. Chem. 1995, 38, 2893.
17. Long, Y. Q.; Xue, T.; Song, Y. L.; Liu, Z. L.; Huang, S. X.; Yu, Q. J. Med. Chem. 2008,
51, 6371.
References and notes
1. For a review, see:Hydrolysis and Formation of CeO Bonds; Drauz, K., Waldmann,
H., Eds.Enzyme Catalysis in Organic Synthesis; VCH: Weinheim, 1995; Vol. 1,
pp 165e371.
18. Meyer, H. Ber. 1906, 39, 198.
19. Wang, M.-X.; Lu, G.; Ji, G.-J.; Huang, Z.-T.; Meth-Cohn, M.; Colby, J. Tetrahedron:
Asymmetry 2000, 11, 1123.
20. Lee, M.; Jin, Y.-H.; Dong, H.; Kim, B. Med. Chem. 1999, 7, 1755.
2. For reviews on amidases in organic synthesis, see: (a) Sugai, T.; Yamazaki, T.;
Yokoyama, M.; Ohta, H. Biosci. Biotechnol. Biochem. 1997, 61, 1419; (b) Martin-
kova, L.; Kren, V. Biocat. Biotrans. 2002, 20, 73.