Asymmetric total synthesis of a beer-aroma constituent based on enantioconvergent biocatalytic hydrolysis of trisubstituted epoxides

Article abstract of DOI:10.1055/s-2001-17713

A short asymmetric total synthesis of the plant constituent myrcenediol [(R)-1], and (S)-7,7-dimethyl-6,8-dioxabicyclo [3.2.1]octane (2), which is a volatile constituent of the aroma of beer was accomplished via a chemoenzymatic protocol. The key step consisted of a biocatalytic hydrolysis of trisubstituted epoxides bearing olefinic side chains which proceeded in an enantioconvergent fashion, i.e., a single enantiomeric vic-diol was obtained from the racemate in up to 91% ee and 92% isolated yield.

Full text of DOI:10.1055/s-2001-17713

PAPER
2035
Asymmetric Total Synthesis of a Beer-Aroma Constituent Based on
Enantioconvergent Biocatalytic Hydrolysis of Trisubstituted Epoxides
E
nantioconvergen
n
B
iocatalytic
d
H
ydrolysis
r
of
T
risub
e
stituted Ep
a
oxides s Steinreiber, Sandra F. Mayer, Kurt Faber*
Department of Chemistry, Organic and Bio-organic Chemistry, University of Graz, Heinrichstrasse 28, 8010 Graz, Austria
Fax +43(316)3809840; E-mail: Kurt.Faber@KFUNIGRAZ.AC.AT
Received 11 June 2001; revised 27 July 2001
using tartaric acid as chiral starting material,11 through
resolution,12 or via asymmetric cycloaddition employing
Oppolzer’s chiral sultam13 and Sharpless dihydroxyla-
tion.14 Retrosynthetic analysis showed that both of the tar-
Abstract: A short asymmetric total synthesis of the plant constitu-
ent myrcenediol [(R)-1], and (S)-7,7-dimethyl-6,8-dioxabicyc-
lo[3.2.1]octane (2), which is a volatile constituent of the aroma of
beer was accomplished via a chemoenzymatic protocol. The key
step consisted of a biocatalytic hydrolysis of trisubstituted epoxides get compounds are easily accessible via an
bearing olefinic side chains which proceeded in an enantioconver-
gent fashion, i.e., a single enantiomeric vic-diol was obtained from
the racemate in up to 91% ee and 92% isolated yield.
enantioconvergent biocatalytic hydrolysis of trisubstitut-
ed epoxides bearing suitable olefinic side chains as the
key step (Scheme 1).
Key words: epoxide hydrolase, enantioconvergent hydrolysis,
trisubstituted epoxide, beer-aroma
R1
O
OH
OH
R
O
R
O
*
R
R =
rac
Bacterial epoxide hydrolases have been shown to be high-
ly versatile biocatalysts for the preparation of nonracemic
vic-diols. In particular, sterically more demanding 2,2-
disubstituted epoxides were hydrolyzed with excellent se-
lectivities (E-values up to >200)1 and for 2,3-disubstituted
analogues, the biohydrolysis was shown to proceed in an
enantioconvergent fashion, i.e., only a single stereoiso-
meric vic-diol was formed from the rac-epoxide in 100%
theoretical yield.2 Most recently, this phenomenon of
enantio-convergence was also observed for trialkyl-ox-
iranes.3 In order to apply this highly efficient method for
the generation of nonracemic vic-diols to natural product
synthesis, we investigated trisubstituted epoxides bearing
olefinic side chains, which would serve as functional
groups for further (oxidative) transformations. From our
previous studies4,5 it was anticipated that these lipophilic
substrates would be well accepted by epoxide hydrolases.
In this context, epoxides possessing a terpenoid structural
framework seemed to be an attractive synthetic target.
1 R =
1
2 R = H
1
3 R = CH
3
Scheme 1 Retrosynthetic analysis
Epoxides rac-4 and rac-5 were prepared from commer-
cially available alkenes 4a and 5a via chemoselective ep-
oxidation of the electron-rich internal C=C bond using m-
chloroperbenzoic acid in 83% yield (Scheme 2). The ab-
sence of spontaneous hydrolysis in aqueous buffer was
verified for both substrates in the absence of biocatalyst
and was shown to be negligible (<3%) within the antici-
pated reaction time of ~48 hours.
In order to find a suitable biocatalyst, rac-4 and rac-5
were screened for hydrolytic activity using resting cells of
a range of pigment-producing bacteria which are known
to possess epoxide hydrolase activity (Table 1). In each
case, where activity was observed, the corresponding diol
1 or 6, respectively, was the only detectable product.
Myrcenediol (1) is a plant constituent, which was isolated
from the roots of Bidens graveolens6 and from the flowers
of Tanacetum annuum.7 Neither its enantiomeric excess
nor its absolute configuration was investigated. The (R)-
enantiomer of 1, which was synthesized via four steps
from myrcene (4a) using Baker’s yeast reduction of a ke-
tone for the introduction of chirality, served as chiral
building block for the synthesis of Hippospongic Acid A.8
OH
OH
m-chloroperbenzoic
bacterial epoxide
hydrolase
O
R
acid / CH Cl
2
2
sole product
R
R
buffer pH 7.5
4a
5a
rac-4
rac-5
(R)-1
(R)-6
R =
R =
1, 4, 4a
The (S)-enantiomer of 7,7-dimethyl-6,8-dioxabicyc-
lo[3.2.1]octane (2) is known as a volatile contributor to
the aroma of beer9 and was first isolated from Japanese
hop oil.10 Asymmetric synthesis of 2 was accomplished
5, 5a, 6
Scheme 2 Synthesis of substrates and biocatalytic hydrolysis
Table 1 shows the stereoselectivities [given as conversion
(c) and enantiomeric purities of substrate (eeS) and prod-
uct (eeP)]15 obtained in the biohydrolysis of rac-4 and rac-
5. Substrate 4 was hydrolyzed with low to acceptable se-
lectivities by several strains with the predominant forma-
Synthesis 2001, No. 13, 08 10 2001. Article Identifier:
1437-210X,E;2001,0,13,2035,2039,ftx,en;Z06401SS.pdf.
© Georg Thieme Verlag Stuttgart · New York
ISSN 0039-7881

2036
A. Steinreiber et al.
PAPER
Table 1 Stereoselectivities from the Biocatalytic Hydrolysis of rac-4 and rac-5
Substrate
Entry
4
5
Strain
Conversiona ee Epoxide ee Diol
(%)
Conversionb ee Epoxide ee Diol
(%)
1
2
3
4
5
6
7
8
Rhodococcus ruber DSM 44540
Rhodococcus ruber DSM 44539
Rhodococcus ruber DSM 44541
Rhodococcus equi IFO 3730
64
46
65
73
54
29
10
2
86 (R)
85 (R)
87 (R)
9 (R)
78 (R)
83 (R)
7 (S)
86 (R)
60 (R)
85 (R)
85 (R)
40 (S)
34 (R)
14 (R)
22 (R)
80
82
78
64
71
71
4
75 (S)
64 (S)
59 (S)
7 (R)
82 (R)
82 (R)
77 (R)
50 (R)
60 (R)
81 (R)
44 (S)
96 (R)
Rhodococcus sp. CBS 717.73
8 (S)
Mycobacterium paraffinicum NCIMB 10420
Arthobacter sp. DSM 312
> 99 (R)
3 (R)
Streptomyces lavendulae ATCC 55209
<1
6
5 (R)
aAfter 48 h.
bAfter 40 h.
tion of (R)-1 in up to 86% ee, except for Rhodococcus sp. dently synthesized material.8 The overall yield from
CBS 717.73, which produced the (S)-enantiomer (entry alkene 4a to (R)-1 was 68%.
5). Several data sets of c, eeS and eeP clearly indicated that
the transformation does not follow a kinetic resolution
pathway, which is most striking for entries 1, 3, 4 and 5.
In a similar fashion, (R)-2-methyl-7-octene-2,3-diol (6)
was obtained from rac-5 (211 mg) using 1.0 g of lyo-
philized Rhodococcus ruber DSM 44540 cells in 90%
Similar results were obtained for substrate rac-5. Again, yield and 90% ee. The unexpected higher enantiomeric
the formation of (R)-6 was predominant with a single ex- excess of the product at elevated conversion (compare en-
ception (Arthobacter sp. DSM 312, entry 7). The clear in- try 1) can be attributed to the assumption that the slower
dication of a non-kinetic-resolution-type was even more reacting (S)-enantiomer of the epoxide is transformed
evident for substrate rac-5, in particular for entries 1–6 with higher regioselectivity than the (R)-counterpart.3 Ox-
and the possibility of an enantioconvergent transforma- idation of (R)-6 by ozonolysis, followed by acid-catalyzed
tion - as indicated by a high eeP at conversion far beyond ring-closure in a one-pot reaction gave (R)-2 in 80% yield
the 50%-benchmark - is evident for entries 1–3.
and 95% ee (Scheme 3). The overall yield of the reaction
sequence from alkene 5a to (R)-6 was 60%.
The mechanistic reason for this enantioconvergent path-
way is the fact that both enantiomers are hydrolyzed with
opposite regioselectivity, whereas the (S)-enantiomer of
the oxirane is attacked by [OH–] at the less substituted ox-
irane carbon atom with concomitant inversion of configu-
ration, the (R)-enantiomer is transformed via retention
through attack at the fully substituted oxirane carbon at-
om. Both pathways lead to the formation of an (R)-config-
urated diol from a rac-epoxide as the sole product.3
O
/PPh
3
3
O
/PPh
3
3
p-TosOH
p-TosOH
(R)-2
(R)-3
(S)-2
(S)-3
(CF SO
) O
2 2
80%
3
77%
OH
O
OH
Py
94%
PdCl cat./CuCl
2
R
2
R
PdCl cat./CuCl
2 2
MeO(CH ) OMe
(S)-5
MeO(CH ) OMe
2 2
(R)-6
2 2
23%
R =
25%
Scheme 3 Enantio-complementary chemoenzymatic synthesis of
both enantiomers of bicyclic acetals 2 and 3
For preparative-scale biotransformations, Rhodococcus
ruber DSM 44540 was chosen as the prime candidate,
since it gave best selectivity for rac-4 and was proven to
be suitable towards upscaling.16 Unfortunately, the most
selective strain for substrate rac-5 (Streptomyces laven-
dulae ATCC 55209) was hampered by insufficient reac-
tion rates.
Since no bacterial strain produced (S)-6 in high ee - which
is required for the synthesis of the naturally occurring (S)-
enantiomer of 2 - the (R)-enantiomer was used as starting
material instead. Inversion of the stereogenic center was
achieved via an epoxide-closing-reopening sequence,
which proceeded with inversion and retention of absolute
configuration, respectively.17–19 Thus, diol (R)-6 (ee 95%)
was transformed into the corresponding trifluoromethane
sulfonate20 followed by immediate ring-closure in the
presence of base (3 equivalents of pyridine) to give (S)-5
in 94% yield and 95% ee. In order to effect a stereochem-
Thus, hydrolysis of rac-4 (50 mg) using 0.2 g of resting
cells of Rhodococcus ruber DSM 44540 in Tris-buffer
(pH 8.0) gave 52 mg of (R)-Myrcenediol (1) in 92% yield
and 83% ee as the sole product. The absolute configura-
tion of 1 was determined by comparison with indepen-
Synthesis 2001, No. 13, 2035–2039 ISSN 0039-7881 © Thieme Stuttgart · New York

PAPER
Enantioconvergent Biocatalytic Hydrolysis of Trisubstituted Epoxides
2037
g, 40.6 mmol) were added and the suspension was stirred for 3 h.
After the reaction was complete, solids were filtered and the filtrate
was treated with Na2S2O5 (10%, 200 mL). After phase separation,
the organic phase was washed with sat. NaHCO3 (3 200 mL),
dried and evaporated. Kugelrohr distillation yielded pure epoxides
4 and 5, details and spectroscopic data are given below.
ically ‘clean’ hydrolysis with complete retention of con-
figuration under acidic conditions,17–21 the crude product
had to be purified. Best results were achieved using a
THF–H2O mixture (1:1) and H2SO4 as catalyst. Thus 80
mg of (S)-5 (ee 95%) gave 71 mg of (S)-6 in 79% yield
and 92% ee, which indicated that only a trace amount of
racemization took place. The overall yield for the inver-
sion sequence was 74%. Ozonolysis followed by acid-cat-
alyzed acetal formation of (S)-5 gave (S)-2 in 77% yield
and 92% ee.
6,7-Epoxy-7-methyl-3-methylene-1-octene
Epoxidation of 4a (3.0 g, 24.0 mmol) yielded after Kugelrohr distil-
lation (43 mbar, 115–120 °C) 4 (2.81 g, 83%) as a colorless liquid.
Rf (PE–EtOAc, 1:1) = 0.85 (detection II).
1H NMR data were in full agreement with those previously report-
In order to show the flexibility of the method, both enan-
tiomers of the desmethyl-analogue (3) of the hop-oil in-
gredient were synthesized via Wacker oxidation of 6
using PdCl2 as catalyst, and CuCl2 as reoxidant. Thus 490
mg of (R)-6 were transformed into 110 mg of (R)-3 (ee
93%). Analogous results were obtained for the (S)-enanti-
omer.
ed.26
13C NMR (90.55 MHz, CDCl3): = 18.68, 24.76, 27.47, 28.30,
58.36, 63.98, 113.31, 116.03, 138.48, 145.34.
2,2-Dimethyl-3-pent-4-enyloxirane
Epoxidation of 5a (2.0 g, 14.3 mmol) gave after Kugelrohr distilla-
tion (40 mbar, 125–30 °C) 5 (0.93 g, 83%) as a colorless liquid. Rf
(PE–EtOAc, 1:1) = 0.78 (detection II); spectroscopic data were in
full agreement with those previously reported.27
In conclusion, we have demonstrated that the enantiocon-
vergent hydrolysis of trisubstituted epoxides bearing ole-
finic side chains using bacterial epoxide hydrolases
proceeded in a highly selective manner, which provided
the corresponding vic-diols in almost quantitative yield.
The latter compounds were transformed into terpenoid
natural products in nonracemic form in a straightforward
manner.
2-Methyl-6-methylene-7-octene-2,3-diol [(R)-1]
Lyophilized cells of Rhodococcus ruber DSM 44540 (0.2 g) were
rehydrated in Tris-buffer (15 mL, pH 8.0, 50 mM) for 1 h and rac-
4 (50 mg, 1.5 mmol) was added in one portion. The mixture was in-
cubated at 30 °C for 200 h with shaking at 130 rpm. The solution
was extracted thrice with CH2Cl2 (10 mL), dried (Na2SO4) and con-
centrated. After flash chromatography, (R)-1 (52 mg, 92%, ee 83%)
was isolated as a colorless oil. Rf (PE–EtOAc, 1:1) = 0.36 (detec-
tion II); spectroscopic data were in full agreement with those previ-
ously reported.28
NMR spectra were recorded in CDCl3 using a Bruker AMX 360 at
360 MHz (1H) and 90 MHz (13C), or a Bruker DMX Avance 500 at
500 MHz (1H) and 125 MHz (13C). Chemical shifts are reported rel-
ative to TMS ( = 0.00 ppm) with CHCl3 as internal standard [ =
7.23 (1H) and 76.90 ppm (13C)], coupling constants (J) are given in
Hz. 13C NMR multiplicities were determined by using a DEPT
2-Methyl-7-octene-2,3-diol [(R)-6]
Lyophilized cells of Rhodococcus ruber DSM 44540 (1.0 g) were
rehydrated in Tris-buffer (60 mL, pH 8.0, 50 mM) for 1 h and rac-
5 (211 mg, 1.5 mmol) was added in one portion. The mixture was
incubated for 143 h at 30 °C. The solution was extracted 5 times
with CH2Cl2 (40 mL), dried (Na2SO4) and concentrated. After flash
chromatography (R)-6 was isolated as a colorless oil (213 mg, 90%,
ee 90%). Rf (PE–EtOAc, 1:1) = 0.32 (detection II); spectroscopic
data were in full agreement with those previously reported.14
pulse sequence. TLC plates were run on silica gel Merck 60 (F254
)
and compounds were visualized by spraying with vanillin/concd
H2SO4 (5 g/L) (detection I), or by dipping into a KMnO4 reagent
[2.5 g/L KMnO4 in H2O] (detection II). Compounds were purified
either by flash chromatography on silica gel Merck 60 (230–400
mesh) or, for volatile compounds, by Kugelrohr distillation. Petro-
leum ether (PE) with boiling range of 60–90 °C was used. GC anal-
yses were carried out on a Varian 3800 gas chromatograph
equipped with FID and either a HP1301 or a HP1701 capillary col-
umn (both 30 m, 0.25 mm, 0.25 m film, N2). Enantiomeric purities
were analyzed using a CP-Chirasil-DEX CB column (25 m, 0.32
mm, 0.25 m film) with H2 as carrier gas. Solvents were dried and
freshly distilled by common practice. For anhydrous reactions,
flasks were dried at 150 °C and flushed with dry Ar just before use.
Myrcene (4a, technical grade) and 7-methyl-1,6-octadiene (5a)
were purchased from Aldrich. m-Chloroperbenzoic acid (70%, m-
CPBA) from Fluka was used. Lyophilized bacterial cells were used
for biotransformations. Bacteria were obtained from culture collec-
tions; the following strains (which were previously referred to the
culture collection of the Institute of Biotechnology, Graz University
of Technology), were classified and deposited at DSMZ (Braunsch-
weig, Germany): Nocardia EH1 = Rhodococcus ruber SM
1789 = DSM 44540; Nocardia TB1 = Rhodococcus ruber SM
1790 = DSM 44539; Nocardia H8 = Rhodococcus ruber SM
1788 = DSM 44541; all strains were grown as previously de-
scribed.22–25
7,7-Dimethyl-6,8-dioxabicyclo[3.2.1]octane [(S)-2]
Diol (S)-6 (30 mg, 0.19 mmol, ee 92%) was dissolved in anhyd
CH2Cl2 (5 mL). The solution was cooled to –80 °C and O3 was bub-
bled through until the blue color persisted. Excess O3 was removed
with a stream of Ar. PPh3 (40 mg, 0.15 mmol) was added and the
solution was allowed to warm to r.t. over 2 h. p-Toluenesulfonic
acid (10 mg) was added and the solution was stirred overnight. The
solution was washed with sat. NaHCO3 (5 mL) and dried (Na2SO4).
After concentration in vacuo at 0 °C, the crude product was purified
by flash chromatography on silica gel (pentane–Et2O, 95:5) to yield
(S)-2 (21 mg, 77%, ee 94%) as a colorless liquid. Spectroscopic data
were in full agreement with those previously reported.13
[ ]20D –79.96 (c 0.50, CHCl3).
Rf (PE–EtOAc, 1:1) = 0.78, (detection I).
7,7-Dimethyl-6,8-dioxabicyclo[3.2.1]octane [(R)-2]
Diol (R)-6 (270 mg, 1.7 mmol, ee 91%) was treated with O3, PPh3
and p-toluenesulfonic acid as described above to yield (R)-2 (194
mg, 80%, ee 95%) as a colorless liquid. Spectroscopic data were
identical to those of (S)-2.
Epoxidation of 4a and 5a to furnish 4 and 5; General Procedure
Alkene 4a or 5a (35 mmol) was dissolved in CH2Cl2 (300 mL) and
cooled to 0 °C. K2CO3 (9.5 g, 68.7 mmol) and m-CPBA (70%, 10.0
[ ]D20+80.32 (c 0.64, CHCl3).
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2038
A. Steinreiber et al.
PAPER
5,7,7-Trimethyl-6,8-dioxabicyclo[3.2.1]octane [(R)-3]
Determination of Absolute Configuration
Diol (R)-6 (490 mg, 3.1 mmol, ee 91%) was dissolved in anhyd 1,2-
dimethoxyethane (10 mL). The solution was stirred at r.t., PdCl2
(0.10 g, 0.56 mmol) and CuCl2 (0.58 g, 4.3 mmol) were added and
stirring was continued for 12 h. The brown solution was diluted
with H2O and Et2O (10 mL each). After phase separation, the aque-
ous layer was extracted twice with Et2O (5 mL). The combined or-
ganic phases were dried (Na2SO4) and concentrated. After flash
chromatography (pentane–Et2O, 10:1), (R)-3 (110 mg, 23%, ee
93%) was isolated as a colorless liquid.
Absolute configurations of the biotransformation products were de-
termined via co-injection with independently synthesized standard
material on GC using a chiral stationary phase. Reference material
was obtained as follows: Sharpless dihydroxylation of 2-methyl-
2,7-octadiene using -AD-mix14 gave (S)-4 (ee 87%).
Diol (R)-1 was synthesized based on a procedure previously de-
scribed:8 Oxidation of rac-1 (50 mg, 0.30 mmol) with pyridinium-
SO3 complex (150 mg, 0.94 mmol) in anhyd DMSO (3 mL) yielded
2-methyl-6-methylene-2-hydroxy-oct-7-en-3-one (30 mg, 61%).
Rf (PE–EtOAc, 1:1) = 0.84 (detection I).
1H NMR (500.13 MHz, CDCl3): = 1.29 (s, 3 H), 1.38 (s, 3 H), 1.43
(s, 3 H), 1.56–1.66 (m, 4 H), 1.89 (m, 2 H), 1.89 (s, 1 H).
13C NMR (125.76 MHz, CDCl3): = 17.57, 21.35, 24.67, 26.27,
29.62, 34.61, 81.28, 81.56, 107.72.
Rf (PE–EtOAc, 5:1) = 0.59 (detection I).
1H NMR (500.13 MHz, CDCl3): = 5.01 (s, 1 H), 5.06 (s, 1 H), 5.11
(d, 1 H, J = 10.8 Hz), 5.29 (d, 1 H, J = 17.6 Hz), 6.38 (dd, 1 H,
J = 17.6, 10.9 Hz).
13C NMR (125.76 MHz, CDCl3): = 25.43, 26.51, 29.74, 34.45,
76.23, 113.72, 116.47, 138.30, 144.92, 213.77.
5,7,7-Trimethyl-6,8-dioxabicyclo[3.2.1]octane [(S)-3]
Diol (S)-6 (292mg, 1.8 mmol, ee 92%) was oxidized using the
Wacker-oxidation procedure described above to yield (S)-3 (71.4
mg, 25%, ee 96%). Spectroscopic data were identical to those of
(R)-3.
The latter material was reduced with Baker´s yeast to furnish (R)-1
(ee 93%, yield 20%).
Screening of Biocatalysts for the Hydrolysis of 4 and 5; General
Procedure
Inversion Procedure for (R)-6 to (S)-6
rac-Epoxides 1a, 2a and 3a (5 L) were hydrolyzed using rehydrat-
ed lyophilized cells (50 mg) in Tris-buffer (1 mL, 0.05 M, pH 8.0)
by shaking the mixture at 30° C with 130 rpm. After 24 h and 48 h,
aliquots of these solutions (0.5 mL) were extracted twice with
EtOAc (0.5 mL each). To facilitate phase separation, the cells were
removed by centrifugation. The combined organic layers were dried
and analyzed by GC on a chiral stationary phase.
Diol (R)-6 (180 mg, 1.1 mmol, ee 91%) was dissolved in anhyd
CH2Cl2 (5 mL) under Ar and pyridine (0.25 mL, 3.12 mmol) was
added. The solution was cooled to 0 °C and trifluoromethanesulfon-
ic anhydride (0.23 mL, 1.37 mmol) was added. After 1 h the solu-
tion was washed with 5% HCl (5 mL) and sat. NaHCO3 (5 mL). The
organic phase was dried (Na2SO4) and concentrated. After flash
chromatography (pentane–Et2O, 5:1), (S)-5 (150 mg, 94%, ee 95%)
was isolated as a colorless liquid. Epoxide (S)-5 (80 mg, 0.57 mmol)
was dissolved in THF–H2O (1:1, 2 mL) and 6 N H2SO4 (2 drops) Acknowledgement
was added. The solution was stirred for 2 h and extracted twice with
This work was performed within the Spezialforschungsbereich Bio-
EtOAc (2 mL). The organic phase was washed with sat. NaHCO3 (4
mL) and dried (Na2SO4). After flash chromatography (pentane–
Et2O, 2:1), (S)-6 was isolated as a colorless oil in 74% overall yield
(71 mg, ee 92%). Spectroscopic data were in full agreement with
those previously reported.14
katalyse (SFB-A4, project no. F-104) and was financed by the
Fonds zur Förderung der wissenschaflichen Forschung and the Au-
strian Ministry of Science (Vienna).
References and Notes
Synthesis of Reference Material for rac-Diols 1 and 6
Diols ( )-1 and ( )-6 were obtained by acid-catalyzed hydrolysis of
the corresponding rac-oxiranes 4 and 5 (0.2 M in H2O–THF, 1:1
containing 3–4 drops of 6 N H2SO4). Extractive workup and flash
chromatography (PE–EtOAc, 5:1) gave pure diols ( )-1 and ( )-6.
Spectral data of these reference compounds matched those of mate-
rial obtained from biotransformations and were in full agreement
with those previously reported.14
(1) Orru, R. V. A.; Faber, K. Curr. Opinion Chem. Biol. 1999,
3, 16.
(2) Kroutil, W.; Mischitz, M.; Faber, K. J. Chem. Soc., Perkin
Trans. 1 1997, 3629.
(3) Steinreiber, A.; Mayer, S. F.; Saf, R.; Faber, K. Tetrahedron:
Asymmetry 2001, 12, 1519.
(4) Steinreiber, A.; Osprian, I.; Mayer, S. F.; Orru, R. V. A.;
Faber, K. Eur. J. Org. Chem. 2000, 3703.
Table 2 GC-Analyses of Enantiomeric Compositions
(5) Osprian, I.; Stampfer, W.; Faber, K. J. Chem. Soc., Perkin
Trans. 1 2000, 3779.
(6) Bohlmann, F.; Ahmed, M.; King, R. M.; Robinson, H.
Phytochemistry 1983, 22, 1281.
(7) Barrero, A. F.; Sanchez, J. F.; Altarejos, J.; Zafra, M. J.
Phytochemistry 1992, 31, 1727.
(8) Hioki, H.; Ooi, H.; Mimura, Y.; Yoshio, S.; Kodama, M.
Synlett 1998, 729.
(9) Tressl, R.; Friese, L.; Fendesack, F.; Köppler, H. J. Agric.
Food Chem. 1978, 26, 1422.
(10) Naya, Y.; Kotake, M. Tetrahedron Lett. 1967, 26, 2459.
(11) (a) Masaki, Y.; Nagata, K.; Serizawa, Y.; Kaji, K. Tennen
Yuki Kagobutsu Toronkai Koen Yoshishu 1983, 26, 545.
(b) Chem. Abstr. 1983, 101, 23162x.
Compound Conditions
tR (min) (Absolute Config.)
6.53 (S), 6.79 (R)
1
2
3
4
6
5
12 psi He, 135 °C (iso)
12 psi He, 100 °C (iso)
20 psi He, 100 °C (iso)
12 psi He, 125 °C (iso)
12 psi H2, 125 °C (iso)
12 psi H2, 125 °C (iso)
4.25 (R), 4.32 (S)
2.34 (R), 2.45 (S)
18.12 (R), 18.60 (S)
3.32 (S), 3.48 (R)
6.60 (S), 6.92 (R)
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Enantioconvergent Biocatalytic Hydrolysis of Trisubstituted Epoxides
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Synthesis 2001, No. 13, 2035–2039 ISSN 0039-7881 © Thieme Stuttgart · New York