Chemoenzymatic approach to optically active phenylglycidates: Resolution of bromo- and iodohydrins

Article abstract of DOI:10.1016/j.tetasy.2004.08.026

Enantiomerically enriched phenylglycidates, precursors of the taxol C-13 phenylisoserine side chain and diltiazem, were prepared by kinetic resolution of anti-2-bromo-3-hydroxy- and anti-3-hydroxy-2-iodophenylpropanoates to provide enantioriched (2R,3R)- and (2S,3S)-halohydrins. The bulkiness and inflexibility of bromo and iodo groups in halohydrins have made them inaccessible to the active site of most of the lipases utilized for the hydrolysis of their acyloxy derivatives. In a set of 22 hydrolases screened herein, including native as well as commercial enzymes, only Aspergillus niger (Lipase AS, AMANO) could catalyze the hydrolysis with high enantioselectivity (E = 176). The resolved halohydrins easily underwent transformation to the corresponding (2S,3R)- and (2R,3S)-phenylglycidates.

Full text of DOI:10.1016/j.tetasy.2004.08.026

Tetrahedron:
Asymmetry
Tetrahedron: Asymmetry 15 (2004) 3131–3138
Chemoenzymatic approach to optically active
phenylglycidates: resolution of bromo- and iodohydrins
Naveen Anand,a Munish Kapoor,a Surrinder Koul,a Subhash C. Taneja,a,*
Rattan L. Sharmab and Ghulam N. Qazia
aBiotechnology Division, Regional Research Laboratory, Jammu 180 001, India
bDepartment of Chemistry, University of Jammu, Jammu 180 005, India
Received 7 July 2004; accepted 23 August 2004
Abstract—Enantiomerically enriched phenylglycidates, precursors of the taxol C-13 phenylisoserine side chain and diltiazem, were
prepared by kinetic resolution of anti-2-bromo-3-hydroxy- and anti-3-hydroxy-2-iodophenylpropanoates to provide enantioriched
(2R,3R)- and (2S,3S)-halohydrins. The bulkiness and inflexibility of bromo and iodo groups in halohydrins have made them inaccessible
to the active site of most of the lipases utilized for the hydrolysis of their acyloxy derivatives. In a set of 22 hydrolases screened herein,
including native as well as commercial enzymes, only Aspergillus niger (Lipase AS, AMANO) could catalyze the hydrolysis with high
enantioselectivity (E = 176). The resolved halohydrins easily underwent transformation to the corresponding (2S,3R)- and (2R,3S)-
phenylglycidates.
ꢀ 2004 Elsevier Ltd. All rights reserved.
1. Introduction
bromo- and iodohydrins are ideal precursors of the corre-
sponding glycidates. On the other hand, larger atomic
size and rigidity of bromine/iodine in these substrates
may also be a limiting factor in the approach and fitting
into the active sites of most of the hydrolases.5 The bulk-
iness and steric effects of the substituents may cause
obstruction in the interactions with the enzyme, which
in turn may not allow the reaction to take off.6 In view
of this, it would be interesting to investigate lipase cata-
lyzed hydrolysis of a-halo-b-hydroxyphenylpropionates
in presence of bromo or iodo groups.
Enantiomerically enriched phenylglycidates, important
intermediates of the phenylisoserine side chain in the
anti-cancer drug taxol1 and anti-anginal drug dil-
tiazem,2,3 (Scheme 1) have reportedly been prepared
by kinetic resolution of chlorohydrins as they are easily
accepted by lipases/esterases.4a,b However, both bromo-
and iodohydrins are much less studied as substrates for
hydrolases. The larger atomic sizes of both bromine and
iodine make them better leaving groups, hence both
O
COOR
OCH3
O
O
(2S,3R)
S
COOR
Ph
NH
O
OAc
or
Ph
OH
O
N
H3CO
COOR
O
OH
(2R,3S)
.HCl
N
(2R,3S)
Scheme 1.
*
Corresponding author. Tel.: +91 191 2572002; fax: +91 191 2548607/2543829; e-mail: sc_taneja@yahoo.co.in
0957-4166/$ - see front matter ꢀ 2004 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tetasy.2004.08.026

3132
N. Anand et al. / Tetrahedron: Asymmetry 15 (2004) 3131–3138
During our research programme on the kinetic resolu-
tion of chiral drugs/drug intermediates and chiral syn-
thons/auxiliaries,7 we envisaged the preparation of
optically active phenylglycidates through kinetic resolu-
tion of anti-bromo- and iodohydrins as both the
resolved enantiomers can easily be converted (via
syn-glycidates) to the isoserine side chain of taxol by dif-
ferent synthetic routes8 whereas p-methoxyphenylglyci-
date can be converted to diltiazem.2 Furthermore,
both bromo- and iodohydrin analogues are easy to han-
dle as they are more stable and crystalline in nature and,
unlike chlorohydrins, these compounds can be obtained
exclusively as anti-isomers. Moreover we were also inter-
ested in studying the effect of higher molecular weight
halohydrins on the kinetics as well as enantioselectivity.
stituted cinnamates 1 were subjected to a cohalogen-
ation reaction using potassium bromate or periodic
acid9 to exclusively generate anti-a-halo-b-hydroxy-
phenylpropionates 2a–h in 65–77% yields.
Initially racemic substrates 2a–h were subjected to
kinetic resolution studies through stereoselective hydrol-
ysis using native as well as commercial hydrolases10
so as to obtain enantiomerically enriched 2-halo-3-
hydroxyphenylpropanoic acid and their carboxylate
esters. Not surprisingly, none of the hydrolases used
(22 in total) could facilitate (Scheme 3) the hydrolysis
of the substrates. It clearly highlights the influence of
bulkier atoms, such as bromine and iodine in halohydrin
esters, in causing steric hindrance during hydrolysis,
even though many of the enzymes used in the present
study (e.g., PSL, PPL, CCL, AK, MAP 10) have
reportedly been successfully used in hydrolyzing the
corresponding chlorohydrin propionates.4a
A detailed survey of the literature revealed that not
many attempts have been made in the past to prepare
phenylglycidates through kinetic resolution of halohyd-
rins, though there is a report, which describes the reso-
lution of a chlorohydrin4a (comprising both syn and
anti or mixture) in order to synthesize enantiomerically
pure precursors of the C-13 side chain of taxol.
It is well known that alkyl acyloxy esters can be easily
hydrolyzed by lipases, therefore 2a–h were converted
to the corresponding acyloxy esters 3a–h in almost
quantitative yields (Scheme 2). It was expected that most
of the lipases would be able to stereoselectively hydro-
lyze the acyloxy ester group in substrates 3a–h (Scheme
4).
2. Results and discussion
Herein we report the preparation of anti-2-bromo-3-
hydroxyphenylpropanoate and anti-3-hydroxy-2-iodo-
phenylpropanoate and the application of lipases for
their resolution and further conversion to (2R,3S)- and
(2S,3R)-phenylglycidates 6 and 7, respectively. In the
proposed reaction in Scheme 2, unsubstituted and sub-
Hence, we undertook the kinetic resolution of 3a–h; this
time only Aspergillus niger (Lipase AS, Amano) could
effect the hydrolysis of acetoxy ester in aqueous buffer,
furnishing (2R,3R)-2-halo-3-hydroxyphenylpropanoates
4a–h in reasonable yield. All other lipases used earlier,
OR2
OH
COOR
COOR
COOR
i or ii
iii
X
X
R1
R1
R1
1
3a-h
2a-h
3a-h
2a-h
(a) R = Me; R1= H; X = Br
(b) R = Et; R1= H; X = Br
(c) R = Me; R1= H; X = I
(d) R = Et; R1= H; X = I
(e) R = Me; R1= OMe; X = Br
(f) R = Et; R1= OMe; X = Br
(g) R = Me; R1= OMe; X = I
(h) R = Et; R1= OMe; X = I
(a) R = Me; R1= H; R2= COCH3, COC2H5, COC3H7; X = Br
(b) R = Et; R1= H; R2= COCH3, COC2H5, COC3H7; X= Br
(c) R = Me, R1= H, R2= COCH3, COC2H5, COC3H7; X = I
(d) R = Et, R1= H, R2= COCH3, COC2H5, COC3H7; X = I
(e) R = Me, R1= OMe, R2= COCH3, COC2H5, COC3H7; X = Br
(f) R = Et, R1= OMe, R2= COCH3, COC2H5, COC3H7; X = Br
(g) R = Me, R1= OMe, R2= COCH3, COC2H5, COC3H7; X = I
(h) R = Et, R1= OMe, R2= COCH3, COC2H5, COC3H7; X = I
Scheme 2. Reagents and conditions: (i) KBrO3/NaHSO3; (ii) HIO4/NaHSO3; (iii) alkanoic acid anhydride/DMAP.
OH
OH
OH
COOR
COOH
COOR
Lipase
+
X
X
X
R1
R1
R1
2a-h
X = Br, I: R = Me, Et; R1 = H, OMe
Scheme 3.

N. Anand et al. / Tetrahedron: Asymmetry 15 (2004) 3131–3138
OR2
3133
OR2
OH
COOR
COOR
COOR
Lipase
+
X
X
X
R1
R1
R1
3a-h
5a-h
X = Br, I; R = Me, Et; R1 = H, OMe, R2 = COCH3, COC2H5, COC3H7
4a-h
Scheme 4.
OAc
OAc
OH
COOR
COOR
COOR
Lipase
+
X
X
X
R1
R1
R1
(2S,3S)
5
(2R,3R)
4
X = Br, I; R = Me, Et; R1 = H, OMe
Scheme 5.
Table 1. Lipase AS catalyzed hydrolysis of ( )-acetoxy ester 3a–h in
aqueous buffer phase
again completely failed to hydrolyze these substrates,
even in the presence of organic co-solvents or in ionic
liquids. These observations support the results of some
previous studies carried out on the steric requirements
of lipases11 where it had been specified that lipases such
as those belonging to genus Pseudomonas, Candida,
Mucor, etc. are capable of accepting only small to med-
ium sized groups, while lipase from A. niger can accom-
modate comparatively larger groups. Previously Itoh et
al.12 had also carried out some experiments to study the
behaviour of lipase A6 (Aspergillus sp.) on the acylates
of a-alkylthio-b-hydroxyphenyl derivatives and ob-
served that anti-isomers were more compatible for
hydrolysis in comparison to syn-isomer. An increase in
the size of the acyl alkyl group (at C-3) to either propyl
or methylthiomethyl was also well accepted by the A6
lipase. However, the effect of neighbouring large atoms
such as bromine or iodine at C-2 on hydrolytic behav-
iour has not been studied. However, our studies clearly
showed that A. niger lipase was able to hydrolyze only
the acetates (R2 = COCH3) in ( )-3a–h (Scheme 5),
whereas higher alkyl homologues such as propionates
(R2 = COC2H5) and butyrates (R2 = COC3H7) failed
to hydrolyze. These experiments also provide some
indications about the size and width of the cavity at
the active site of lipase from A. niger.
Substrate Time (h)
Alcohol
(4a–h)
Ester
(5a–h)
Conv. Ec
(%)
25
Ee% ½aꢁD
25
a
a
Ee% ½aꢁD
3a
3b
3c
3d
3e
3f
96
24
60
77
93
71
85
59
13
72
ꢂ13.0 18
ꢂ13.1 56
0.0b 17
+9.9 23
+27.6 42
+10.3 15
+11.6 26
+27.5 43
+35.2 45
+17.5 33
+12.0 24
5
13
32
8
96
100
96
ꢂ7.0 19
ꢂ3.9 66
ꢂ10.9 48
ꢂ1.4 26
ꢂ3.4 19
24
6
24
24
3g
3h
1
98
8
a The specific rotations were determined in CHCl3 with c = 1.
25
b
½aꢁD ¼ ꢂ3:5 (c 1, CH3OH).
c Calculated according to Chen et al.13
polar as well as polar solvents in the ratio of 5–30%
v/v buffer were used in the resolution studies and finally
toluene found to be the co-solvent of choice in terms of
conversion rates as well as enantioselectivity, as depicted
in Table 2 for substrate 3c. Addition of toluene as the
co-solvent (10% v/v) in buffer reduced the reaction time
significantly (18h, conversion ꢀ 44%) and also contrib-
uted to improving the ee (93–97.4%). Furthermore, the
addition of acetonitrile (10% v/v) also proved to be ben-
eficial (12h, conversion ꢀ 40%, ee ꢀ 97%) however, it
had its limitations as a co-solvent as the reaction
proceeded well only with liquid substrates and became
slow in presence of insoluble solids substrates.
All kinetic resolution reactions were carried out in an
aqueous phosphate buffer where the rate of hydrolysis
was slow and enantioselectivity was also poor (Table
1). In some substrates, even after 100h of reaction time,
conversions beyond 26% could not be achieved. All
attempts to achieve hydrolysis at C-1 including the
attempts of transesterification (organic solvents/ionic
liquids) proved unsuccessful.
Any further increase in the ratio of the acetonitrile in the
buffer had a detrimental effect on the lipase activity as
well as the rate of hydrolysis. Therefore, toluene was
selected as the co-solvent for detailed kinetic resolution
studies of other substrates. In general, kinetic resolution
studies of compounds 3a–f (where R2 = COCH3) using
toluene as the co-solvent displayed comparatively faster
With the aim to improve the rate of hydrolysis as well as
the enantioselectivity, use of a co-solvents14 was envis-
aged as a practical option. A biphasic system using an
organic solvent proved to be advantageous. Both non-

3134
Table 2. Effect of co-solvents on Amano AS catalyzed hydrolysis of ( )-acetoxy ester 3c
OAc
N. Anand et al. / Tetrahedron: Asymmetry 15 (2004) 3131–3138
OAc
OH
COOMe
COOMe
COOMe
Lipase
+
I
I
I
R1
R1
R1
(2S,3S)
5c
(2R,3R)
4c
3c
Organic co-solvent
Time (h)
EeS (%) 4c
EeP (%) 5c
Conv. (%)
Ea
32
None
144
18
22
12
76
15
76
81
63
78
93
14
44
49
40
47
Toluene
Acetone
Acetonitrile
Hexane
97.4
82
176
24
97
85
128
28
a Calculated according to Chen et al.13
Table 3. Lipase AS catalyzed hydrolysis of ( )-acetoxy ester 3a–h with toluene as co-solvent
Substrate
Time (h)
Alcohol (4a–h)
Ester (5a–h)
Conv. (%)
Ec
25
½aꢁD
25
½aꢁD
a
a
Ee%
Yield (%)
Ee%
Yield (%)
3a
3b
3c
3d
3e
3f
24
24
18
20
48
50
45
42
94
89
ꢂ19.9
ꢂ15.5
0.0b
42
43
46
45
44
42
41
42
70
73
76
60
77
63
75
77
+41.3
+37.5
+48.0
+36.0
+32.4
+44.5
+50.5
+49.0
42
41
44
44
45
40
44
43
43
45
44
40
49
46
43
47
69
37
97.4
96
176
95
ꢂ9.5
93
88
ꢂ4.3
84
35
ꢂ16.9
ꢂ10.2
ꢂ4.4
3g
3h
97.3
89
162
41
a The specific rotations were measured in CHCl3 with c = 1.
25
b
½aꢁD ¼ ꢂ3:8 (c 1, CH3OH).
c Calculated according to Chen et al.13
conversion rates as well as improved enantioselectivity.
The results of these experiments are presented in
Table 3.
yield, while the enriched (2S,3S)-acetoxy esters 5 were
first hydrolyzed to the corresponding (2S,3S)-halohyd-
rins in 2M HCl/MeOH and then finally converted to
(2R,3S) phenylglycidates 7 (Scheme 6) in the presence
of DBU/CH2Cl2 without effecting the enantiomeric
excess. Typically the reaction was over within 20–
30min.
As both (2R,3S)- and (2S,3R)-phenylglycidate enantio-
mers can easily be utilized for their conversion to the re-
quired isoserine side chain, hence further enrichment of
the partially enriched (2S,3S)-esters 5a–f (R2 = COCH3)
was envisaged through double kinetic resolution.
Through these experiments, the enantiomeric excess of
acetoxy esters could be further improved from
ee ꢀ 60% to ee ꢀ 96–99% as shown in Table 4.
3. Conclusions
The influence of the bulkiness and rigidity of the bro-
mine and iodine atoms in anti-2-bromo-3-hydroxy-
and anti-3-hydroxy-2-iodophenylpropanoates and the
intermediates of (2S,3R)- and (2R,3S)-phenylglycidates
was apparent when all the lipases except A. niger (lipase
AS, Amano) completely failed to hydrolyze the carboxyl-
ates and/or acyloxy esters. Only A. niger could easily
resolve their acetates in high enantiopurity. The use
of toluene and acetonitrile further improved the rate
of hydrolysis as well as enantioselectivity. Double
kinetic resolution studies also improved the enantio-
purity of the optically enriched unhydrolyzed acetoxy
esters. Resolved bromo- and iodohydrins underwent
facile conversion to the corresponding glycidates in
almost quantitative yields with no change in
enantiopurity.
The enriched (2R,3R)-halohydrins 4 could easily be con-
verted to (2S,3R)-phenylglycidates 6 in quantitative
Table 4. Double kinetic resolution of enantiomerically enriched
acetoxy esters 5a–f
25
Substrate Ee% subs. Time (h) Conv. (%) Ee% DKa ½aꢁD
5a
5b
5c
5d
5e
5f
70
73
76
60
77
83
36
42
38
36
33
28
15
18
13
22
13
10
99
+51.2
+51.5
+60.5
+53.5
+40.6
+53.2
98.8
97
96.3
96.7
96.5
a DK = double kinetic resolution; the specific rotations were measured
in CHCl3 with c = 1.

N. Anand et al. / Tetrahedron: Asymmetry 15 (2004) 3131–3138
3135
OH
O
COOR
COOR
DBU, 5oC
CH2Cl2
X
R1
R1
(2R,3R)
(2S,3R)
4
6
OH
OAc
O
COOR
COOR
COOR
dil HCl
CH3OH
DBU, 5oC
CH2Cl2
X
X
R1
R1
R1
(2S,3S)
(2S,3S)
X = Br, l: R = Me, Et; R1 = H, OMe
(2R,3S)
7
5
Scheme 6.
4. Experimental
(200MHz): d 3.80 (3H, s, –COOCH3), 4.38 (1H, d,
J = 8.2Hz, CH–Br), 5.07 (1H, d, J = 8.2Hz, CH–OH),
7.38 (5H, s, Ar–H). 13C NMR (50MHz): d 47.4, 53.2,
75.3, 127.0, 128.6, 128.8, 139.0, 171.9. MS (m/z):
(M+1) 260, 258, 243, 199, 162, 98. Anal. Calcd for
C10H11BrO3: C, 46.36; H, 4.28. Found: C, 46.52; H,
4.30.
4.1. General
1H and 13C NMR were recorded on a Bruker (200 and
50MHz) spectrometer in CDCl3 using TMS as the inter-
nal standard. IR was recorded on a FT-IR Bruker
(270-30) spectrophotometer. Elemental analysis was per-
formed on an Elementar CHNS analyzer. Mass spectra
were recorded on LC–MS Bruker and Shimadzu GC–
MSQP2000. Optical rotations were measured on a Per-
kin–Elmer 241 polarimeter in the indicated solvents
and concentrations. TLC was performed on Silica gel
60 F254 (Merck). The enantiomeric excesses (ee) were
measured by chiral HPLC (Shimadzu) on (R,R)-
Whelk-01 and Chiralcel OD-H chiral columns using
hexane/isopropyl alcohol/acetic acid in 97:3:0.1. Melting
points were determined on Buchi B-542 apparatus by
open capillary method and are uncorrected. Lipase AS
ꢀAmanoꢁ batch no LAY0651455S was a gift from Ama-
no Enzyme Inc., Japan. All the reagents and enzymes
were used directly without further purification.
4.3. Preparation of ethyl ( )-anti-2-bromo-3-hydroxy-3-
phenylpropanoate 2b
Compound 2b was prepared from ethyl cinnamate
(3.52g, 20.0mmol) following the procedure described
in Section 4.2 (3.80g, 70%), mp 76–77ꢁC. IR (KBr):
3446, 2993, 1720, 1376, 1285, 1185, 1152, 1016, 871,
770, 700cmꢂ1 1H NMR (200MHz): d 1.27 (3H, t,
.
J = 7.1Hz, –COOCH2CH3), 4.25 (2H, q, J = 7.1Hz,
–COOCH2), 4.36 (1H, d, J = 8.1Hz, CH–Br), 5.08
(1H, d, J = 8.1Hz, CH–OH), 7.38 (5H, s, Ar–H). 13C
NMR (50MHz): d 14.0, 47.8, 62.5, 75.3, 127.1, 128.7,
128.9, 140.4, 169.6. MS (m/z): (M+1) 274, 272, 229,
193, 166, 148, 81. Anal. Calcd for C11H13BrO3: C,
48.41; H, 4.80. Found: C, 48.16; H, 4.80.
4.2. Preparation of methyl ( )-anti-2-bromo-3-hydroxy-
3-phenylpropanoate 2a
4.4. Preparation of methyl ( )-anti-3-hydroxy-2-iodo-3-
phenylpropanoate 2c
Potassium bromate (4.00g, 24.0mmol) was dissolved in
water (40mL) and adjusted to pH <3 with dil H2SO4.
To the resultant solution was added methyl cinnamate
(3.24g, 20.0mmol) dissolved in acetonitrile (40mL) fol-
lowed by 1M sodium bisulfate solution (5.20g in 50mL
water) added over a period of 3h with stirring at 40ꢁC.
The reaction mixture was further stirred for 36h until
the reaction was complete. The resulting solution was
extracted with ethyl acetate (3 · 50mL), and the com-
bined organic layers were washed with aqueous sodium
sulfite and dried over anhydrous sodium sulfate. The
contents were concentrated in vacuo to give the crude
material, which on crystallization (benzene–hexane
1:1) furnished 2a, (3.50g, 70%), mp 63ꢁC. IR (KBr):
3506, 2952, 1729, 1436, 1377, 1286, 1206, 1176, 1145,
In a stirred solution comprising of methyl cinnamate
(3.26g, 20.0mmol) and HIO4Æ2H2O (5.20g, 24.0mmol)
in acetonitrile (40mL) at 25ꢁC, a solution of 1M sodium
bisulfate (5.50g in 50mL water) was added over a period
of 3h. The reaction mixture was further stirred for 48h
at 25ꢁC until the reaction was complete. Usual work-up
and purification as described for 2a afforded 2c
(4.50g, 73%), mp 63ꢁC. IR (KBr): 3434, 2925, 1735,
1
1437, 1284, 1203, 999, 766cmꢂ1. H NMR (200MHz):
d 3.76 (3H, s, –COOCH3), 4.57 (1H, d, J = 8.5Hz,
CH–I), 5.06 (1H, d, J = 8.5Hz, CH–OH), 7.37 (5H, s,
Ar–H). 13C NMR (50MHz): d 24.5, 53.1, 76.2, 127,
128.6, 128.8, 139.4, 171.7. MS (m/z): 306, 291, 275,
187, 186, 162, 119. Anal. Calcd for C10H11IO3: C,
39.24; H, 3.62. Found: C, 39.34; H, 3.57.
1006, 920, 773, 722, 700, 651, 597cmꢂ1 1H NMR
.

3136
N. Anand et al. / Tetrahedron: Asymmetry 15 (2004) 3131–3138
4.5. Preparation of ethyl ( )-anti-3-hydroxy-2-iodo-3-
phenylpropanoate 2d
(50MHz): d 25.4, 53.1, 55.4, 75.8, 114.3, 128.2, 131.6,
160.2, 171.7. MS (m/z): (M+1) 337, 192, 161, 138, 137,
109. Anal. Calcd for C11H13IO4: C, 39.31; H, 3.90.
Found: C, 39.48; H, 3.92.
Compound 2d was prepared from ethyl cinnamate
(3.52g, 20.0mmol) following the procedure as described
for 2c (4.80g, 75%), mp 79ꢁC. IR (KBr): 3436, 2993,
4.9. Preparation of ethyl ( )-anti-3-hydroxy-2-iodo-3-(4-
methoxyphenyl)propanoate 2h
1719, 1376, 1286, 1185, 1152, 1015, 871, 772, 700cmꢂ1
.
1H NMR (200MHz): d 1.28 (3H, t, J = 7.1Hz,
–COOCH2CH3), 4.24 (2H, q, J = 7.1Hz, –COOCH2),
4.58 (1H, d, J = 8.3Hz, CH–I), 5.08 (1H, d, J = 8.3Hz,
CH–OH), 7.38 (5H, s, Ar–H). 13C NMR (50MHz): d
13.7, 25.1, 62.1, 76.2, 126.9, 128.5, 128.6, 139.4, 171.2.
MS (m/z): 320, 275, 229, 193, 166. Anal. Calcd for
C11H13IO3: C, 41.27; H, 4.09. Found: C, 41.67; H,
4.02.
Compound 2h was prepared from 4-methoxy ethyl cin-
namate (4.12g, 20.0mmol) following the procedure as
described for 2c to give 2h (4.50g, 65%), mp 108–
109ꢁC. IR (KBr): 3436, 1736, 1610, 1513, 1253, 1118,
838cmꢂ1
. d 1.28 (3H, t,
1H NMR (200MHz):
J = 7.1Hz, –COOCH2CH3), 3.82 (3H, s, –OCH3), 4.25
(2H, q, J = 7.1Hz, –COOCH2), 4.54 (1H, d,
J = 8.5Hz, CH–I), 5.04 (1H, d, J = 8.5Hz, CH–OH),
6.91 (2H, d, J = 8.7Hz, Ar–H), 7.31 (2H, d,
J = 8.7Hz, Ar–H). 13C NMR (50MHz): d 14.1, 25.7,
55.7, 62.5, 76.2, 114.3, 128.6, 132.0, 160.1, 171.6. MS
(m/z): 350, 223, 206, 177, 161, 109. Anal. Calcd for
C12H15IO4: C, 41.16; H, 4.32. Found: C, 41.48; H,
4.40.
4.6. Preparation of methyl ( )-anti-2-bromo-3-hydroxy-
3-(4-methoxyphenyl)-propanoate 2e
Compound 2e was prepared from 4-methoxy methyl
cinnamate (3.84g, 20.0mmol) following the procedure
as described for 2a (3.80g, 66%), mp 59–60ꢁC. IR
(KBr): 3300, 1734, 1612, 1517, 1167, 834cmꢂ1 1H
.
4.10. Preparation of methyl ( )-anti-3-acetoxy-2-bromo-
3-phenylpropanoate 3a
NMR (200MHz): d 3.81 (6H, s, –COOCH3 and
–OCH3), 4.35 (1H, d, J = 8.6Hz, CH–Br), 5.04 (1H, d,
J = 8.6Hz, CH–OH), 6.91 (2H, d, J = 8.7Hz, Ar–H),
7.32 (2H, d, J = 8.7Hz, Ar–H). 13C NMR (50MHz): d
47.6, 53.0, 55.2, 74.7, 113.8, 128.1, 131.1, 159.7, 169.8.
MS (m/z): (M+1) 290, 288, 209, 203, 175, 119, 109,
107. Anal. Calcd for C11H13BrO4: C, 45.73; H, 4.54.
Found: C, 46.27; H, 4.56.
A solution of 2a (2.59g, 10.0mmol), acetic anhydride
(1.22g, 12.0mmol) and DMAP (5mg) in dichlorometh-
ane (10mL) was kept overnight at room temperature.
After completion of the reaction, the contents were
poured into ice-cold water and extracted with dichloro-
methane (3 · 50mL). The organic layer was washed,
dried and evaporated to furnish the crude product,
which on purification by column chromatography over
silica gel with ethyl acetate–n-hexane (3:97) as eluent
gave 3a (2.86g, 95%), mp 56ꢁC. IR (KBr): 3006, 1732,
4.7. Preparation of ethyl ( )-anti-2-bromo-3-hydroxy-3-
(4-methoxyphenyl)-propanoate 2f
1
1436, 1372, 1234, 1130, 1013, 926, 768cmꢂ1. H NMR
Compound 2f was prepared from 4-methoxy ethyl
cinnamate (4.12g, 20.0mmol) following the procedure
as described for 2a (4.20g, 70%), mp 70–72ꢁC. IR
(200MHz): d 1.99 (3H, s, –OCOCH3), 3.80 (3H, s,
–COOCH3), 4.64 (1H, d, J = 10.7Hz, CH–Br), 6.15
(1H, d, J = 10.7Hz, CH–OAc), 7.38 (5H, s, Ar–H).
13C NMR (50MHz): d 20.6, 22.4, 53.1, 76.7, 128.0,
128.5, 129.2, 136.6, 168.7, 169.8. MS (m/z): (M+1) 302,
243, 221, 189, 179, 161, 149, 131. Anal. Calcd for
C12H13BrO4: C, 47.86; H, 4.35. Found: C, 47.84; H,
4.27.
(KBr): 3443, 1742, 1611, 1514, 1251, 1149, 838cmꢂ1
.
1H NMR (200MHz): d 1.26 (3H, t, J = 7.1Hz,
–COOCH2CH3), 3.80 (3H, s, –OCH3), 4.16 (2H, q,
J = 7.1Hz, –COOCH2), 4.25 (1H, d, J = 8.6Hz, CH–
Br), 5.04 (1H, d, J = 8.6Hz, CH–OH), 6.90 (2H, d,
J = 8.7Hz, Ar–H), 7.35 (2H, d, J = 8.7Hz, Ar–H). 13C
NMR (50MHz): d 13.8, 48.0, 55.3, 62.3, 74.8, 113.9,
128.2, 131.3, 159.8, 169.5. MS (m/z): (M+1) 304, 302,
259, 257, 207, 178, 177, 161, 138, 137, 135, 121, 107,
94. Anal. Calcd for C12H15BrO4: C, 47.54; H, 4.99.
Found: C, 47.39; H, 5.06.
4.11. Preparation of ethyl ( )-anti-3-acetoxy-2-bromo-3-
phenylpropanoate 3b
Compound 3b was prepared from 2b (2.73g, 10.0mmol),
acetic anhydride (1.22g, 12.0mmol) and DMAP (5mg)
following the procedure for 3a (2.93g, 93%). IR (neat):
4.8. Preparation of methyl ( )-anti-3-hydroxy-2-iodo-3-
(4-methoxyphenyl)-propanoate 2g
2984, 1746, 1371, 1268, 1221, 1147, 1020, 763cmꢂ1
.
1H NMR (200MHz): d 1.30 (3H, t, J = 7.1Hz,
–COOCH2CH3), 2.00 (3H, s, –OCOCH3), 4.27 (2H, q,
J = 7.1Hz, –COOCH2), 4.48 (1H, d, J = 10.0Hz, CH–
Br), 6.10 (1H, d, J = 10.0Hz, CH–OAc), 7.40 (5H, s,
Ar–H). 13C NMR (50MHz): d 14.5, 21.3, 46.9, 62.9,
76.1, 128.5, 128.6, 129.8, 136.6, 168.2, 169.2. MS (m/z):
315, 301, 293, 277, 252, 236, 233, 217, 212, 211, 195,
196, 170, 154. Anal. Calcd for C13H15BrO4: C, 49.56;
H, 4.80. Found: C, 50.04; H, 4.71.
Compound 2g was prepared from 4-methoxy methyl
cinnamate (3.84g, 20.0mmol) following the procedure
as described for 2c (4.30g, 65%), mp 86–87ꢁC. IR
(KBr): 3300, 1734, 1612, 1517, 1167, 834cmꢂ1 1H
.
NMR (200MHz): d 3.78 (3H, s, –COOCH3), 3.82
(3H, s, –OCH3), 4.55 (1H, d, J = 8.5Hz, CH–I), 5.05
(1H, d, J = 8.5Hz, CH–OH), 6.90 (2H, d, J = 8.7Hz,
Ar–H), 7.30 (2H, d, J = 8.7Hz, Ar–H). 13C NMR

N. Anand et al. / Tetrahedron: Asymmetry 15 (2004) 3131–3138
3137
4.12. Preparation of methyl ( )-anti-3-acetoxy-2-iodo-3-
phenylpropanoate 3c
(1H, d, J = 10.1Hz, CH–Br), 6.08 (1H, d, J =
10.1Hz, CH–OAc), 6.90 (2H, d, J = 8.7Hz, Ar-H),
7.32 (2H, d, J = 8.7Hz, Ar–H). 13C NMR (50MHz): d
14.0, 20.9, 46.7, 53.3, 62.3, 75.3, 113.9, 128.1, 129.3,
160.1, 167.8, 168.8. MS (m/z): 345, 265, 223, 222, 219,
177, 109, 91, 90, 89. Anal. Calcd for C14H17BrO5: C,
48.71; H, 4.96. Found: C, 49.13; H, 5.08.
Compound 3c was prepared from 2c (3.06g, 10.0mmol),
acetic anhydride (1.22g, 12.0mmol) and DMAP (5mg)
following the procedure as described for 3a (3.30g,
95%), mp 57–58ꢁC. IR (KBr): 3006, 2953, 1732, 1436,
1375, 1234, 1130, 1013, 764cmꢂ1
.
1H NMR
(200MHz): d 2.01 (3H, s, –OCOCH3), 3.81 (3H, s,
–COOCH3), 4.65 (1H, d, J = 10.7Hz, CH–I), 6.15 (1H,
d, J = 10.7Hz, CH–OAc), 7.37 (5H, s, Ar–H). 13C
NMR (50MHz): d 20.7, 22.5, 53.1, 77.0, 128.0, 128.5,
129.2, 136.6, 168.7, 169.8. MS (m/z): 348, 273, 263,
220, 204, 198, 182, 167, 166, 151, 150, 140, 124, 108,
96, 80. Anal. Calcd for C12H13IO4: C, 41.40; H, 3.76.
Found: C, 41.03; H, 3.80.
4.16. Preparation of methyl ( )-anti-3-acetoxy-2-iodo-3-
(4-methoxyphenyl)-propanoate 3g
Compound 3g was prepared from 2g (3.36g, 10.0mmol),
acetic anhydride (1.22g, 12.0mmol) and DMAP (5mg)
following the procedure described for 3a (3.40g, 90%),
mp 58ꢁC. IR (neat): 3451, 3005, 2951, 1735, 1611,
1435, 1375, 1022, 958, 830, 777cmꢂ1
.
1H NMR
(200MHz): d 1.99 (3H, s, –OCOCH3), 3.80 (3H, s,
–COOCH3), 3.82 (3H, s, –OCH3), 4.64 (1H, d,
J = 10.8Hz, CH–I), 6.12 (1H, d, J = 10.8Hz, CH–
OAc), 6.90 (2H, d, J = 8.7Hz, Ar–H), 7.33 (2H, d,
J = 8.7Hz, Ar–H). 13C NMR (50MHz): d 20.7, 22.9,
53.1, 55.7, 76.8, 113.8, 128.7, 129.3, 160.1, 168.7,
169.9. MS (m/z): 378, 335, 251, 208, 133, 108. Anal.
Calcd for C13H15IO5: C, 41.30; H, 4.00. Found: C,
41.80; H, 4.04.
4.13. Preparation of ethyl ( )-anti-3-acetoxy-2-iodo-3-
phenylpropanoate 3d
Compound 3d was prepared from 2d (3.19g, 10.0mmol),
acetic anhydride (1.22g, 12.0mmol) and DMAP (5mg)
following the procedure as described for 3a to furnish
3d (3.28g, 91%). IR (neat): 2982, 1738, 1371, 1263,
1
1222, 1017, 967, 699cmꢂ1. H NMR (200MHz): d 1.29
(3H, t, J = 7.1Hz, –COOCH2CH3), 1.98 (3H, s,
–OCOCH3), 4.27 (2H, q, J = 7.1Hz, –COOCH2), 4.62
(1H, d, J = 10.8Hz, CH–I), 6.15 (1H, d, J = 10.8Hz,
CH–OAc), 7.38 (5H, s, Ar–H). 13C NMR (50MHz): d
13.8, 20.6, 23.1, 62.1, 76.7, 128.0, 128.4, 129.1, 136.6,
168.6, 169.2. MS (m/z): 362, 236, 215, 194, 177, 150,
147, 132, 108, 105, 91. Anal. Calcd for C13H15IO4: C,
43.12; H, 4.18. Found: C, 43.23; H, 4.22.
4.17. Preparation of ethyl ( )-anti-3-acetoxy-2-iodo-3-(4-
methoxyphenyl)-propanoate 3h
Compound 3h was prepared from 2h (3.50g, 10.0mmol),
acetic anhydride (1.22g, 12.0mmol) and DMAP (5mg)
following the above procedure (3.56g, 91%), mp 51–
53ꢁC. IR (neat): 2981, 1739, 1612, 1516, 1371, 1252,
1
1224, 1177, 1019, 967, 832cmꢂ1. H NMR (200MHz):
d 1.30 (3H, t, J = 7.1Hz, –COOCH2CH3), 1.98 (3H, s,
–OCOCH3), 3.81 (3H, s, –OCH3), 4.26 (2H, q,
J = 7.1Hz, –COOCH2), 4.61 (1H, d, J = 10.9Hz, CH–
I), 6.12 (1H, d, J = 10.9Hz, CH–OAc), 6.90 (2H, d,
J = 8.7Hz, Ar–H), 7.34 (2H, s, J = 8.7Hz, Ar-H). 13C
NMR (50MHz): d 13.8, 20.7, 23.6, 55.2, 62.0, 76.4,
113.8, 128.7, 129.3, 160.1, 168.7, 169.4. MS (m/z): 392,
347, 333, 262, 222, 213, 206, 189, 179, 137, 132. Anal.
Calcd for C14H17IO5: C, 42.87; H, 4.37. Found: C,
43.33; H, 4.44.
4.14. Preparation of methyl ( )-anti-3-acetoxy-2-bromo-
3-(4-methoxyphenyl)-propanoate 3e
Compound 3e was prepared from 2e (2.89g, 10.0mmol),
acetic anhydride (1.22g, 12.0mmol) and DMAP (5mg)
following the procedure as described for 3a (3.11g,
94%). IR (neat): 3004, 2956, 1748, 1612, 1516, 1371,
1
1022, 964, 832cmꢂ1. H NMR (200MHz): d 2.00 (3H,
s, –OCOCH3), 3.81 (3H, s, COOCH3), 3.82 (3H, s,
–OCH3), 4.71 (1H, d, J = 10.2Hz, CH–Br), 6.10 (1H,
d, J = 10.2Hz, CH–OAc), 6.90 (2H, d, J = 8.7Hz, Ar–
H), 7.32 (2H, d, J = 8.7Hz, Ar–H). 13C NMR
(50MHz): d 20.6, 22.8, 53.3, 62.3, 75.3, 113.9, 128.1,
129.3, 160.1, 167.8, 168.8. MS (m/z): 331, 251, 209,
207, 177, 153, 136, 134. Anal. Calcd for C13H15BrO5:
C, 47.13; H, 4.53. Found: C, 47.41; H, 4.49.
4.18. General procedure of lipase catalyzed kinetic
resolution of 3
In a typical experiment, a mixture of substrate 3a
(800mg, 2.7mmol), toluene (1.6mL), crude powder of
enzyme AS Amano (800mg) in 14.4mL phosphate buf-
fer (pH7.0, 0.1M) was stirred at 30 1ꢁC. The course
of the reaction was monitored by chiral HPLC. After
a certain degree of conversion, the reaction was termi-
nated and contents extracted with ethyl acetate
(3 · 50mL), and organic phase washed with water, dried
over sodium sulfate and concentrated in vacuo to give
the crude product, which after column chromatography
4.15. Preparation of ethyl ( )-anti-3-acetoxy-2-bromo-3-
(4-methoxyphenyl)-propanoate 3f
Compound 3f was prepared from 2f (3.03g, 10.0mmol),
acetic anhydride (1.22g, 12.0mmol) and DMAP (5mg)
following the procedure as described for 3a (3.21g,
93%), mp 54–55ꢁC. IR (neat): 2984, 1746, 1371,
1268, 1221, 1147, 1020, 763, 698, 611, 580, 541cmꢂ1
.
on silica gel with ethyl acetate–hexane (3:97) as
¼
25
D
1H NMR (200MHz): d 1.31 (3H, t, J = 7.1Hz,
–COOCH2CH3), 2.00 (3H, s, –OCOCH3), 3.81 (3H, s,
–OCH3), 4.25 (2H, q, J = 7.1Hz, –COOCH2), 4.69
eluent furnished (ꢂ)-4a (385mg, 42%): ee 94%, ½aꢁ
25
ꢂ19:9 (c 1, CHCl3) and (+)-5a (250mg, 42%): ee 70%,
½aꢁ ¼ þ41:3 (c 1, CHCl3).
D

3138
N. Anand et al. / Tetrahedron: Asymmetry 15 (2004) 3131–3138
3. (a) Matsuki, K.; Sobukawa, K.; Kawai, A.; Inoue, H.;
Takeda, M. Chem. Pharm. Bull. 1993, 41, 643–648; (b)
Inoue, H.; Matsuki, K.; Oh-Ishi, T. Chem. Pharm. Bull.
1993, 41, 1521–1523.
4. (a) Wuts, P. G. M.; Gu, R. L.; Northuis, J. M.
Tetrahedron: Asymmetry 2000, 11, 2117–2123; (b) Hama-
moto, H.; Mamedov, V. A.; Kitamoto, M.; Hayashi, N.;
Tsuboi, S. Tetrahedron: Asymmetry 2000, 11, 4485–4497.
5. Kazlauskas, R. J.; Weissfloch, A. N. E.; Rappaport, A. T.;
Cuccia, L. A. J. Org. Chem. 1991, 56(8), 2656–2665.
6. Oberhauser, Th.; Faber, K.; Griengl, H. Tetrahedron 1989,
45, 1679–1682.
4.19. General procedure for the preparation of 6 from 4
In a typical experiment, a mixture of alkyl (2R,3R)-2-
halo-3-hydroxy-3-phenylpropanoate 4 (200mg), DBU
(200lL) in dichloromethane (4mL) was stirred at 5ꢁC
for 5min and gradually warmed to room temperature.
Stirring was continued for another 30min and moni-
tored by TLC. After completion, the contents were di-
luted with dichloromethane (20mL), and the organic
phase washed with water, dried and chromatographed
to give pure alkyl (2S,3R)-phenylglycidates 6.
7. (a) Kapoor, M.; Anand, N.; Koul, S.; Chimni, S. S.;
Manhas, K. S.; Raina, C.; Parshad, R.; Taneja, S. C.;
Qazi, G. N. Bioorg. Chem. 2003, 31, 259–269; (b) Koul, S.;
Parshad, R.; Taneja, S. C.; Qazi, G. N. Tetrahedron:
Asymmetry 2003, 14, 2459–2464, and references cited
therein; (c) Ahmed, K.; Koul, S.; Taneja, S. C.; Singh, A.
P.; Kapoor, M.; Riyaz-ul-Hassan; Verma, V.; Qazi, G. N.
Tetrahedron: Asymmetry 2004, 15, 1685–1692.
8. Gou, D. M.; Liu, Y. C. J. Org. Chem. 1993, 58, 1287–
1289.
9. Masuda, H.; Takase, K.; Nishio, M.; Hasegawa, A.;
Nishiyama, Y.; Ishii, Y. J. Org. Chem. 1994, 59, 5550–
5555.
10. Arthrobacter sp.; Aspergillus niger (Lipase AS); Aspergillus
ochraceus; Aspergillus flavus; Aspergillus fumigator;
Amano acylase; Candida cylindraceae lipase; Candida
rugosa lipase; Candida antarctica lipase; Mucor javanicus;
Mucor miehei; pig liver acetone powder; porcine pancreas
lipase; Pseudomonas cepecia; Pseudomonas sp. on Celite
(Amano PS-C); Pseudomonas fluorescence; Pichia farinosa
(RRLY-4); Physarum polycephalum (RRLY-5); Tricho-
sporon sp. (RRLY-15); Bacillus pumilus (RRL-191);
Bacillus sp. (RRL-1789); Bacillus subtilis (RRL-BB-1).
11. Faber, K. Biotransformations in Organic Chemistry, 4th
ed.; 2000; p 98.
4.20. General procedure for the preparation of 7 from 5
In a typical experiment, alkyl (2S,3S)-3-acetoxy-2-halo-
3-phenylpropanoate 5 (200mg) was dissolved in metha-
nol (4mL). To this was added 2M HCl (200lL) and the
reaction mixture stirred at room temperature for 24h
until the conversion was complete. Excess of solvent
was evaporated and the reaction mixture diluted with
water (10mL) and extracted with ethyl acetate, dried
and evaporated to give alkyl (2S,3S)-2-halo-3-hydroxy-
3-phenylpropanoate, which was converted to 7 follow-
ing the procedure as described for 6.
Acknowledgements
Authors are thankful to Amano Enzyme Inc. Japan for
the gifts of AS, PSL, PS-C and acylase samples.
References
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