Asymmetric epoxidation of styrene derivatives by styrene monooxygenase from Pseudomonas sp. LQ26: Effects of α- And β-substituents

Article abstract of DOI:10.1016/j.tetasy.2010.12.022

Recombinant Escherichia coli expressing a styrene monooxygenase, StyAB2, from Pseudomonas sp. LQ26 was applied to synthesize a range of chiral epoxides from conjugated styrene derivatives with excellent (>99%) enantioselectivity in most cases. The substrate preference was studied with a special focus on the steric effect of α- and β-substituents.

Full text of DOI:10.1016/j.tetasy.2010.12.022

Tetrahedron: Asymmetry 22 (2011) 134–137
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Tetrahedron: Asymmetry
journal homepage: www.elsevier.com/locate/tetasy
Asymmetric epoxidation of styrene derivatives by styrene monooxygenase
from Pseudomonas sp. LQ26: effects of a- and b-substituents
Hui Lin a,b, Yan Liu a, Zhong-Liu Wu a,
⇑
a Chengdu Institute of Biology, Chinese Academy of Sciences, PO Box 416, 9 South Renmin Road, 4th Section, Chengdu, Sichuan 610041, China
b Graduate School of the Chinese Academy of Sciences, Beijing 100039, China
a r t i c l e i n f o
a b s t r a c t
Article history:
Recombinant Escherichia coli expressing a styrene monooxygenase, StyAB2, from Pseudomonas sp. LQ26
was applied to synthesize a range of chiral epoxides from conjugated styrene derivatives with excellent
(>99%) enantioselectivity in most cases. The substrate preference was studied with a special focus on the
Received 29 October 2010
Accepted 14 December 2010
Available online 15 February 2011
steric effect of a- and b-substituents.
Ó 2011 Elsevier Ltd. All rights reserved.
1. Introduction
excellent. Herein we report a systematic study on the performance
of this enzyme in the epoxidation of a series of styrene derivatives,
Enantiopure epoxides are well recognized as extremely impor-
tant building blocks that can be transformed into numerous bio-
logically active targets. They can be formed from a variety of
precursors, among which the asymmetric epoxidation of an olefin
is the most attractive. Considerable effort has been made in this
area by synthetic chemists.1–5 Complementary to this, a number
of enzymatic approaches have also been studied to provide envi-
ronmentally friendly alternatives.6,7
Styrene monooxygenase (SMO) is an enzyme involved in the
upper catabolic pathway of styrene degradation.8 It shows
excellent enantioselectivity in the epoxidation of styrene, to give
(S)-styrene epoxide with >99% ee. The SMO from Pseudomonas
fluorescens VLB120 has been used in a pilot-scale production of
(S)-styrene oxide.9,10 However, its potential as a tool in organic
synthesis remains largely unexplored. Most studies have focused
on its characterization from a biochemical point of view.8,11 Sello
et al. and Schmid et al. studied the bioconversion of substituted
styrenes by SMO from P. fluorescens ST and P. fluorescens VLB120.
However, in most cases, only substrates with substituents on the
with a special focus on the steric effect of a- and b-substituents.
2. Results and discussion
The biotransformations were performed in a biphasic system
catalyzed by the whole cells of a recombinant E. coli BL21(DE3)
bearing
a plasmid encoding StyAB2 from Pseudomonas sp.
LQ26.16 The results are presented in Table 1. All experiments were
performed with the same batch of cells to ensure the same biocata-
lytic activity. For preparative biotransformations, the cell density
used was greater than that in the literature9,10 to ensure the isola-
tion of all products. This condition might have a negative effect on
the catalytic efficiency. Nevertheless, in all cases, (S)-epoxides
were obtained and their enantiomeric excesses were greater than
99% (except entries 5 and 16). The yield of epoxide, however, var-
ied greatly with the substituents.
As shown in the entries 1–12, the bioconversion of a series of
styrene derivatives with substituents ranging from H to propyl
clearly demonstrated a significant steric effect. A substrate with a
bulky substituent yielded fewer products within the same period
of time. In the case of substrates 2a, 5a, 6a, and 9a, all bearing an
R3 group, the yield rapidly decreased from 92% to 58%, 45%, and
12%, respectively, with an increase in the substituent size. Under
the same conditions, styrene 1a yielded >99% of epoxide. Sub-
strates with an i-propyl or n-propyl at the R2 position yielded similar
amounts of product (entry 11 vs 9), which might be due to a flexible
active pocket in the enzyme. The enzyme catalyzed the epoxidation
of cyclic substituted compound 16a (R1,R2 = –(CH2)4–) with 7% yield
and medium enantioselectivity, but could not catalyze the epoxida-
tion of 1-(cyclohexylidenemethyl)benzene (R2,R3 = –(CH2)5–) or
(E)-stilbene (R2 = Ph). It can be inferred that the larger substrates
are less susceptible toward the enzymatic epoxidation process,
benzene ring or
a- and b-methyl substituted styrenes were inves-
tigated.12–15
We recently isolated a novel styrene monooxygenase (desig-
nated StyAB2) from Pseudomonas sp. LQ26 and functionally ex-
pressed it in recombinant Escherichia coli BL21 (DE3) (GenBank
accession no. GU593979).16 It is the most distant member of all
SMOs originating from the genus Pseudomonas. Unlike the SMO
from P. fluorescens ST, this enzyme displays activity toward both
conjugated styrene derivatives and nonconjugated alkenes.16 The
enantioselectivity toward conjugated styrene derivatives remains
⇑
Corresponding author. Tel./fax: +86 28 85238385.
E-mail address: wuzhl@cib.ac.cn (Z.-L. Wu).
0957-4166/$ - see front matter Ó 2011 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tetasy.2010.12.022

H. Lin et al. / Tetrahedron: Asymmetry 22 (2011) 134–137
135
Table 1
Biotransformation of styrene derivatives into the corresponding oxiranes
R1
R1
O
R2
R2
R3
R3
1b-16b
Yieldb (%)
1a-16a
Entry
Substratea
Product
Relative activityc (%)
ee (%)
1
2
3
4
5
6
7
8
9
10
11
12
13
14f
15
16
Styrene 1a
1b
2b
3b
4b
5b
6b
7b
8b
>99
92
87
68
58
45
6
35
12
1
11
5
>99
>99
73g
7
100
97
93
71
64
51
10
39
15
3
15
7
167
271
80
9
>99
R2 = Me 2a
>99
>99
>99
96
>99
>99
>99
>99
>99
>99
>99
R1 = Me 3a
R2, R3 = Me 4a
R2 = –CH@CH2 5a
R2 = Et 6ad
R3 = Et 7ad
R1 = Et 8a
R2 = n-Pr 9ae
9b
R3 = n-Pr 10ae
R2 = i-Pr 11a
10b
11b
12b
13b
14b
14b
16b
R1 = n-Pr 12a
R2 = –CH(OH)CH3 rac-13a
R2 = –CH2OH 14a
R2 = –CH2Cl 15a
R1,R2 = –(CH2)4– 16a
>99 (syn:anti 1:1)
>99
>99
65
O
17
76
77
>99
17a
17b
O
O
O
18
65
70
>99
18a
18b
a
b
c
Substituents other than H were listed.
HPLC yield after 24 h reaction.
Relative activity = [specific activity for substrate a]/[specific activity for styrene] ꢀ 100%; Specific activity for substrate a = mmoles of products formed in 1 h by 1 g of wet
cells.
d
Added as a mixture with 6a:7a = 1:0.8.
Added as a mixture with 9a:10a = 1:0.7.
The reaction was performed without BEHP.
rac-1-Phenylprop-2-en-1-ol 15c isolated with a yield of 17%.
e
f
g
which is consistent with a previous report.12 In contrast, substrates
with aromatic rings larger than styrene, such as 2-vinylnaphthalene
17a and 4-vinyl-2,3-dihydrobenzofuran 18a were well accepted;
both yielded the corresponding (S)-epoxides with >99% enantio-
meric excesses and high yields (entries 17 and 18). It is worth noting
that the product 18b is a critical intermediate in the synthesis of
melatonin agonists. Previously, only indirect biocatalytic methods
using epoxide hydrolase or alcohol reductase have been
described.17
Substrates 13a and 14a bearing a hydroxy group at the b-posi-
tion displayed more than 100% relative activity. Compound 13a
had an additional stereogenic center and was used as a racemate.
The results show that SMO catalyzes the (S)-epoxidation of both
enantiomers almost equally well, resulting in the diastereoisomers
13b1 and 13b2 in a ratio of 1:1, each with an ee value >99%. When
the reaction was traced by HPLC, a maximal de value of 38% (Fig. 1)
was observed, demonstrating a weak ability to distinguish be-
tween the (R)- and (S)-substrates, albeit with steady excellent
selectivity during the epoxidation process. When the hydroxyl
group in 13a was replaced with a chloro or bromo group, no prod-
uct could be detected by HPLC (not listed in Table 1).
Compound 15a did not yield the corresponding epoxide, but
yielded (S)-epoxide 14b. This phenomenon has been reported but
not further explained.12 We found that the real substrate that
underwent bioconversion was 14a. Compound 15a was unstable
in potassium phosphate buffer and would spontaneously trans-
form into 14a and 1-phenylprop-2-en-1-ol 15c, with the former
further converting into 14b. As previously reported, StyAB2 can
catalyze the epoxidation of both conjugated and nonconjugated
olefins,16 and its activity toward 15c has recently been con-
firmed.18 However, it was apparent that the activity of SMO is
higher toward 14a than 15c, demonstrating its preference for con-
jugated substrates, which led to the isolation of unreacted noncon-
jugated olefin 15c.
Our results also show that substituents at the
a
-position (R1)
cause greater steric hindrance than those at the b-position (R2), as
demonstrated by the fact that the bioconversion of substrates 3a,
8a, and 12a resulted in lower product yields than the corresponding
b-substituted substrates 2a, 6a, and 9a. The difference was aug-
mented by an increase in the substituent size, as the relative activ-
ities of b-substituted over
a-substituted substrates were 1.0, 1.3,
and 2.1 for methyl-, ethyl-, and propyl-substituted compounds,
respectively. Furthermore, the reactivity was also affected by the
configuration of the substrates. The (E)-isomers 6a and 9a per-
formed much better than the corresponding (Z)-isomers 7a and
10a. The result was contrary to that observed for SMO from P. fluo-
rescens ST: a preference for (Z)-isomers and accelerated reaction
with methyl-substitution at the R3 position.13 For the SMO from
Pseudomonas sp. LQ26, substituents at the R3 position appeared to
be unfavorable in all the cases tested (entries 2, 3, 6, 7, 9, and 10).

136
H. Lin et al. / Tetrahedron: Asymmetry 22 (2011) 134–137
substrates were from the same batch of culture. The reactions were
carried out at 30 °C for 24 h with shaking at 220 rpm and termi-
nated by extraction with diethyl ether. The organic phase was
dried over anhydrous Na2SO4 and concentrated under reduced
pressure and subjected to reverse phase and chiral HPLC analysis.
To determine the specific activity of various substrates, the reac-
tions were terminated after 1 h and the amount of product was
analyzed using reverse phase HPLC.
For preparative biotransformations, recombinant E. coli BL21
cells with a dry weight of 0.4 g were resuspended in 20 ml of
100 mM potassium phosphate buffer (pH 6.5) containing 10% (v/
v) cyclohexane and 30 mg of substrate. The reactions were carried
out at 30 °C for 24 h with shaking at 220 rpm, and the products
were extracted, concentrated, and subjected to silica gel column
chromatography. The purified products were identified with NMR
analysis and their specific rotations were measured.
Figure 1. Biotransformation of (E)-4-phenylbut-3-en-2-ol 13a with recombinant
E. coli expressing StyAB2.
3. Conclusion
4.2.1. (S)-Styrene oxide 1b
Colorless oil, ee >99% (AS-H, hexane/2-propanol = 90:10, 0.5 ml/
Overall, we have applied a styrene monooxygenase from Pseu-
domonas sp. LQ26 to the synthesis of a spectrum of chiral epoxides
from conjugated styrene derivatives and studied its substrate pref-
min, tR(R) 10.27 min, tR(S) 10.67 min), ½a D25
¼ þ32:1 (c 1.02, CHCl3)
ꢁ
{lit.14
½
a 2D5
ꢁ
¼ þ21:1 (c 83 mM, CHCl3) for 99% ee, (S)} 1H NMR
(600 MHz, CDCl3): d 7.27–7.35 (m, 5H, Ar-H), 3.85 (m, 1H, CH),
erence with a special focus on the steric effects of a- and b-substit-
3.13 (m, 1H, CH2), 2.79 (m, 1H, CH2).
uents. We found that this enzyme is endowed with remarkable
enantioselectivity. To expand its substrate range, the identification
of the critical amino acid residues that interact with these substit-
uents is of great interest. Recently, several mutant enzymes with
altered substrate preference have been observed and are currently
under investigation in this laboratory.
4.2.2. (2S,3S)-2-Methyl-3-phenyloxirane 2b
Colorless oil, ee >99% (AD-H, hexane/2-propanol = 90:10, 1 ml/
min, tR(R) 4.14 min, tR(S) 4.78 min), ½a D25
¼ ꢂ41:8 (c 1.00, CHCl3)
ꢁ
{lit.22
½
a 2D0
ꢁ
¼ þ47:2 (c 1.10, CHCl3) for 99% ee, (R,R)}. 1H NMR
(600 MHz, CDCl3): d 7.25–7.34 (m, 5H, Ar-H), 3.56 (d, J = 1.92 Hz,
1H, CH), 3.01–3.04 (m, 1H, CH), 1.45 (d, J = 5.04 Hz, 3H, CH3).
4. Experimental
1H NMR spectra were recorded on a Brucker-600 (600/150 MHz)
spectrometer in CDCl3. All signals are expressed as ppm down field
from tetramethylsilane. Opticalrotations were measured with a Per-
kin Elmer 341 polarimeter. Chiral HPLC was conducted with a Shi-
madzu Prominence LC-20AD system connected to a PDA-detector
using Daicel Chiralcel OD-H, OJ-H, Chiralpak AD-H, or Whelk-O1(R,
R) columns. Reverse-phase HPLC was conducted using a Luna C18
reverse-phase column (Phenomenex). The absolute configurations
of 1b–5b, 8b, and 12b–18b were established by comparison with
the specific rotation reported in the literature. The absolute config-
urations for all others were based on the analogous chromato-
graphic behavior of racemic mixtures.
Styrene derivatives 1a–4a, 14a–18a were obtained from com-
mercial suppliers and used without further purification. Substrates
5a–12a were prepared by a Wittig reaction.19 Epoxides (S)-1b,
(2S,3S)-2b, and (2R,3R)-2b were obtained from Aldrich. Racemic
epoxides were prepared from the corresponding alkenes in accor-
dance with the literature.20,21
4.2.3. (S)-2-Methyl-2-phenyloxirane 3b
Colorless oil, ee >99% (OD-H, hexane/2-propanol = 90:10,
0.8 ml/min, tR(R) 5.17 min, tR(S) 5.61 min), ½a D25
¼ þ16 (c 0.20,
ꢁ
CHCl3) {lit.14
½
a 2D5
ꢁ
¼ þ19:5 (c 75 mM, CHCl3) for 99% ee, (S)}. 1H
NMR (600 MHz, CDCl3): d 7.25–7.38 (m, 5H, Ar-H), 2.98 (d,
J = 5.3 Hz, 1H, CH2), 2.81 (d, J = 5.3 Hz, 1H, CH2), 1.73 (s, 3H, CH3).
4.2.4. (S)-2,2-Dimethyl-3-phenyloxirane 4b
Colorless oil, ee >99% (AD-H, hexane/2-propanol = 90:10, 1 ml/
min, tR(R) 3.76 min, tR(S) 4.18 min), ½a D25
¼ ꢂ23:6 (c 0.85, benzene)
ꢁ
{lit.1 D = +36.8 (c 0.63, benzene) for 99% ee, (R)}. 1H NMR
[a]
(600 MHz, CDCl3): d 7.18–7.28 (m, 5H, Ar-H), 3.79 (s, 1H, CH),
1.41 (s, 3H, CH3), 1.00 (s, 3H, CH3).
4.2.5. (2S,3S)-2-Phenyl-3-vinyloxirane 5b
Colorless oil, ee 96% (OD-H, hexane/2-propanol = 95:5, 0.5 ml/
min, tR(S,S) 8.7 min, tR(R,R) 9.2 min), ½a D25
¼ ꢂ42:3 (c 0.35, CHCl3)
ꢁ
for purity >99% {lit.23
[
a]
D = ꢂ14.2 (c 0.88, CHCl3) for 95% ee,
(S,S)}. 1H NMR (600 MHz, CDCl3): d 7.28–7.36 (m, 5H, Ar-H),
5.70–5.76 (m, 1H, @CH), 5.52 (d, J = 17.2 Hz, 1H, @CH2), 5.34 (d,
J = 10.56 Hz, 1H, @CH2), 3.76 (d, J = 1.98 Hz, 1H, CH), 3.35–3.37
(dd, J = 1.98 Hz, J = 7.62 Hz, 1H, CH).
4.1. Cultivation of recombinant E. coli BL21 (DE3)
Recombinant E. coli BL21 (DE3) bearing the plasmid encoding
StyAB2 from Pseudomonas sp. LQ26 was cultivated in Terrific Broth
for 3 h at 37 °C, followed by 18 h incubation at 20 °C with gyratory
shaking at 220 rpm.16 Cells were harvested by centrifugation,
washed twice with potassium phosphate buffer (0.1 M, pH 7.0),
and stored at 4 °C.
4.2.6. (E)- and (Z)-1,2-Epoxy-1-phenyl-butane 6b and 7b
Colorless oil, ee >99% (AD-H, hexane/2-propanol = 99:1, 0.5 ml/
min, tR1 9.42 min, tR2 9.98 min (major), tR3 15.28 min (major)) [The
peaks of 6b (S,S) and 7b (R,R) overlapped in the HPLC spectrum,
and the ee values were determined by HPLC in combination with
NMR, which revealed the ratio of 6b and 7b] 1H NMR (600 MHz,
CDCl3): d 7.24–7.34 (m, 5.5H, Ar-H), 4.07 (d, J = 4.2 Hz, 0.1H, CH-
7b), 3.61 (d, J = 1.74 Hz, 1H, CH-6b), 3.14–3.17 (m, 0.1H, CH-7b),
2.92–2.95 (m, 1H, CH-6b), 1.69–1.74 (m, 2H, CH2-6b), 1.20–1.27
(m, 0.2H, CH2-7b), 1.06 (t, J = 7.44 Hz, 3H, CH3-6b), 1.06 (t,
J = 7.62 Hz, 0.3H, CH3-7b).
4.2. General procedure for biotransformation
Recombinant E. coli BL21 cells with a dry weight of 0.2 g were
resuspended in 10 ml of 100 mM potassium phosphate buffer
(pH 6.5) containing 10% (v/v) bis(2-ethylhexyl) phthalate (BEHP)
and 8 mg of substrate. The cells used to transform different

H. Lin et al. / Tetrahedron: Asymmetry 22 (2011) 134–137
137
4.2.7. (S)-2-Ethyl-2-phenyloxirane 8b
4.2.14. (S)-2-(Naphthalen-2-yl)oxirane 17b
Colorless oil, ee >99% (OD-H, hexane/2-propanol = 90:10,
White solid, ee >99% (AD-H, hexane/2-propanol = 90:10, 1 ml/
0.8 ml/min, tR(R) 4.87 min, tR(S) 5.38 min), ½a D25
ꢁ
¼ þ23:1 (c 0.34,
min, tR(R) 13.42 min, tR(S) 14.22 min), ½a D25
¼ þ17 (c 0.72, CHCl3)
ꢁ
CHCl3) {lit.24
½
a 2D5
ꢁ
¼ ꢂ25:2 (c 0.64, CHCl3) for 92% ee, (R)}. 1H
{lit.27
½
a 2D5
ꢁ
¼ ꢂ9 (c 1.2, CHCl3) for 84% ee, (R)}. 1H NMR
NMR (600 MHz, CDCl3): d 7.25–7.37 (m, 5H, Ar-H), 2.97 (d,
J = 5.28 Hz, 1H, CH2), 2.73 (d, J = 5.28 Hz, 1H, CH2), 2.15–2.20 (m,
1H, CH2), 1.78–1.84 (m, 1H, CH2), 0.94 (t, J = 7.8 Hz, 3H, CH3).
(600 MHz, CDCl3): d 7.79–7.82 (m, 4H, Ar-H), 7.44–7.49 (m, 2H,
Ar-H), 7.32 (dd, J = 1.74 Hz, J = 8.4 Hz, 1H, Ar-H), 4.01 (dd,
J = 2.52 Hz, J = 4.14 Hz, 1H, CH), 3.20 (dd, J = 4.14 Hz, J = 5.28 Hz,
1H, CH2), 2.89 (dd, J = 2.52 Hz, J = 5.28 Hz, 1H, CH2).
4.2.8. (E)- and (Z)-1,2-epoxy-1-phenyl-pentan 9b and 10b
Colorless oil, ee >99% (AD-H, hexane/2-propanol = 99:1, 0.5 ml/
min, tR1 9.19 min, tR2 9.63 min, tR3 9.85 min (major), tR4 16.07 min
(major)), 1H NMR (600 MHz, CDCl3): d 7.24–7.34 (m, 5.3H, Ar-H),
4.06 (d, J = 4.26 Hz, 0.1H, CH-10b), 3.61 (d, J = 1.92 Hz, 1H, CH-
9b), 3.18–3.21 (m, 0.1H, CH-10b), 2.93–2.95 (m, 1H, CH-9b),
1.58–1.66 (m, 2H, CH2-9b), 1.50–1.56 (m, 2H, CH2-9b), 1.33–1.37
(m, 0.2H, CH2-10b), 1.21–1.25 (m, 0.2H, CH2-10b), 0.99 (t,
J = 7.5 Hz, 3H, CH3-9b), 1.06 (t, J = 3.3 Hz, 2.1H, CH3-10b).
4.2.15. (S)-4-(Oxiran-2-yl)-2,3-dihydrobenzofuran 18b28
Colorless oil, ee >99% (Whelk-O1(R,R), hexane/2-pro-
pane = 90:10, 1 ml/min, tR(S) 8.10 min, tR(R) 8.72 min),
½
a 2D5
ꢁ
¼ þ40:8 (c 1.0, CHCl3). 1H NMR (600 MHz, CDCl3): d 7.09 (t,
J = 7.92 Hz, 1H, Ar-H), 6.72 (q, J = 7.92 Hz, 2H, Ar-H), 4.59 (t,
J = 7.62 Hz, 2H, CH2), 3.84 (m, 1H, CH), 3.27 (t, J = 7.62 Hz, 2H,
CH2), 3.12 (m, 1H, CH2), 2.83 (m, 1H, CH2).
Acknowledgments
4.2.9. (2S,3S)-2-Isopropyl-3-phenyloxirane 11b
Colorless oil, ee >99% (AD-H, hexane/2-propanol = 90:10, 1 ml/
This work was supported by the National Natural Science Foun-
dation of China (20802073 and 21072183), the 100 Talents Pro-
gram and the Knowledge Innovation Program (KSCX2-YW-G-075)
of the Chinese Academy of Sciences, and Sichuan Province Science
Foundation for Young Scholars 08ZQ026-023.
min, tR(R,R) 3.72 min, tR(S,S) 4.46 min), ½a D25
¼ ꢂ62:4 (c 0.25,
ꢁ
CHCl3). 1H NMR (600 MHz, CDCl3): d 7.25–7.34 (m, 5H, Ar-H),
3.65 (d, J = 1.92 Hz, 1H, CH), 2.75 (dd, J = 1.92 Hz, J = 6.78 Hz, 1H,
CH), 1.65–1.71 (m, 1H, CH), 1.09 (d, J = 6.78 Hz, 3H, CH3), 1.02 (d,
J = 6.78 Hz, 3H, CH3).
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¼ þ32:3 (c 0.26,
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½
a 2D5
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11. O’Leary, N. D.; O’Connor, K. E.; Dobson, A. D. FEMS Microbiol. Rev. 2002, 26, 403–
417.
12. Bernasconi, S.; Orsini, F.; Sello, G.; Colmegna, A.; Galli, E.; Bestetti, G.
Tetrahedron Lett. 2000, 41, 9157–9161.
13. Sello, G.; Orsini, F.; Bernasconi, S.; Di Gennaro, P. Tetrahedron: Asymmetry 2006,
17, 372–376.
14. Schmid, A.; Hofstetter, K.; Feiten, H. J.; Hollmann, F.; Witholt, B. Adv. Synth.
Catal. 2001, 343, 732–737.
15. Bernasconi, S.; Orsini, F.; Sello, G.; Di Gennaro, P. Tetrahedron: Asymmetry 2004,
15, 1603–1606.
4.2.11. (2RS,3S,4S)-3,4-Epoxy-4-phenyl-butan-2-ol 13b
Light yellow oil, ee >99% (AD-H, hexane/2-propane = 90:10,
1 ml/min, tR1 = 6.83 min, tR2 = 7.65 min (major), tR3 = 8.46 min
(major), tR4 = 11.39 min), 1H NMR (600 MHz, CDCl3): d 7.25–7.36
(m, 7H, Ar-H), 4.08–4.11 (m, 2/5H, CH), 3.94 (d, J = 2.1 Hz, 2/5H,
CH), 3.83–3.86 (m, 2H, CH, CH), 3.07–3.08 (m, 2/5H, CH), 3.03–
3.04 (m, 1H, CH), 2.21 (br, 7/5H, OH), 1.35 (d, J = 6.54 Hz, 3H,
CH3), 1.31 (d, J = 6.36 Hz, 7/5H, CH3).
4.2.12. (2S,3S)-3-Phenyloxiran-2-yl methanol 14b
Colorless oil, ee >99% (OD-H, hexane/2-propane = 95:5, 0.5 ml/
min, tR(R) 21.90 min, tR(S) 23.58 min), ½a D25
¼ ꢂ48 (c 0.3, CHCl3)
ꢁ
16. Lin, H.; Qiao, J.; Liu, Y.; Wu, Z.-L. J. Mol. Catal. B: Enzym. 2010, 67, 236–241.
17. Patel, R. N. Coord. Chem. Rev. 2008, 252, 659–701.
18. Lin, H.; Liu, Y.; Wu, Z.-L. Chem. Commun. 2010, doi:10.1039/cocco436oE.
19. Wittig, G.; Schoellkopf, S. Org. Synth. 1973, Coll. 5, 751–754.
20. Hanzlik, R. P.; Edelman, M.; Michaely, W. J.; Scott, G. J. Am. Chem. Soc. 1976, 98,
1952–1955.
{lit.26
[a
]
D = ꢂ49.6 (c 10.5, CHCl3) for 99% ee, (S,S)}. 1H NMR
(600 MHz, CDCl3): d 7.27–7.35 (m, 5H, Ar-H), 3.65 (d, J = 2.1 Hz,
1H, CH), 4.02–4.05 (m, 1H, CH2), 3.92 (d, 3H, CH), 3.77–3.81 (m,
1H, CH2), 3.21–3.22 (m, 1H, CH), 2.10 (br, 1H, OH).
21. Fieser, M.; Fieser, L. F. In Reagents for Organic Synthesis; Wiley-Interscience:
New York, 1967; Vol. 1,
22. Witkop, B.; Foltz, C. M. J. Am. Chem. Soc. 1957, 79, 197–201.
23. Lindström, U. M.; Somfai, P. Synthesis 1998, 109, 117.
24. Warren, J. D.; Shi, Y. J. Org. Chem. 1999, 64, 7675–7677.
25. Wang, B.; Wong, O. A.; Zhao, M.-X.; Shi, Y. J. Org. Chem. 2008, 73, 9539–9543.
26. Di Gennaro, P.; Colmegna, A.; Galli, E.; Sello, G.; Pelizzoni, F.; Bestetti, G. Appl.
Environ. Microbiol. 1999, 65, 2794–2797.
27. Solladie-Cavallo, A.; Diep-Vohuule, A. J. Org. Chem. 1995, 60, 3494–3498.
28. Prasad, J. S.; Vu, T.; Totleben, M. J.; Crispino, G. A.; Kacsur, D. J.; Swaminathan,
S.; Thornton, J. E.; Fritz, A.; Singh, A. K. Org. Process Res. Dev. 2003, 7, 821–827.
4.2.13. (1S,2S)-1-Phenylcyclohexene oxide (16b)
Colorless oil, ee 65% (OD-H, hexane/2-propane = 99:1, 0.5 ml/
min, tR(R,R) 12.53 min, tR(S,S) 13.67 min), ee 65%, ½a D25
¼ ꢂ30:9 (c
ꢁ
1.01, CHCl3) {lit.1
[a]D = +116.7 (c 1.21, benzene) for 99% ee,
(R,R)}. 1H NMR (600 MHz, CDCl3): d 7.23–7.37 (m, 5H, Ar-H), 3.07
(d, 1H, CH), 2.25–2.31 (m, 1H, CH2), 2.09–2.13 (m, 1H, CH2),
1.94–2.03 (m, 2H, CH2), 1.53–1.63 (m, 2H, CH2), 1.40–1.49 (m,
1H, CH2), 1.25–1.32 (m, 1H, CH2).