Chemoenzymatic asymmetric total syntheses of a constituent of Jamaican rum and of (+)-Pestalotin using an enantioconvergent enzyme-triggered cascade reaction

Article abstract of DOI:10.1016/S0957-4166(02)00124-6

A short chemoenzymatic route to two natural products - the first, a constituent of Jamaican rum and the second the (+)-antipode of the gibberelin synergist (-)-Pestalotin - was accomplished based on an enzyme-triggered cascade-reaction. Thus, a racemic halomethyl oxirane was hydrolyzed by bacterial epoxide hydrolases to furnish the corresponding vic-halomethyl-diol, which underwent spontaneous ring-closure to furnish an epoxy alcohol in up to 93% e.e. and ≥99 d.e. Due to the fact that this process was enantioconvergent, the occurrence of the undesired enantiomer was entirely avoided.

Full text of DOI:10.1016/S0957-4166(02)00124-6

TETRAHEDRON:
ASYMMETRY
Pergamon
Tetrahedron: Asymmetry 13 (2002) 523–528
Chemoenzymatic asymmetric total syntheses of a constituent of
Jamaican rum and of (+)-Pestalotin using an enantioconvergent
enzyme-triggered cascade reaction
Sandra F. Mayer,a Andreas Steinreiber,a Marian Goriup,b Robert Safb and Kurt Fabera,*
aDepartment of Chemistry, Organic and Bioorganic Chemistry, University of Graz, Heinrichstrasse 28, A-8010 Graz, Austria
bInstitute for Chemical Technology of Organic Materials, Graz University of Technology, Stremayrgasse 16,
A-8010 Graz, Austria
Received 24 February 2002; accepted 11 March 2002
Abstract—A short chemoenzymatic route to two natural products—the first, a constituent of Jamaican rum and the second the
(+)-antipode of the gibberelin synergist (−)-Pestalotin—was accomplished based on an enzyme-triggered cascade-reaction. Thus,
a racemic halomethyl oxirane was hydrolyzed by bacterial epoxide hydrolases to furnish the corresponding vic-halomethyl-diol,
which underwent spontaneous ring-closure to furnish an epoxy alcohol in up to 93% e.e. and ]99 d.e. Due to the fact that this
process was enantioconvergent, the occurrence of the undesired enantiomer was entirely avoided. © 2002 Elsevier Science Ltd. All
rights reserved.
1. Introduction
ion to furnish a single enantiomeric vic-diol as the sole
product.3 Due to the presence of a halohydrin moiety,
the latter intermediate underwent spontaneous ring-clo-
sure to yield epoxy alcohols (from halomethyl) or THF
derivatives (from haloethyl derivatives) as the final
products in excellent d.e. and e.e.4 Overall, this
exo-7-Butyl-5-methyl-6,8-dioxabicyclo[3.2.1]octane(exo-
1) is a known constituent of Jamaican rum and was first
isolated from a sample of fusel oil, derived from
molasses.1 The relative exo-configuration of 1 was elu-
cidated via NMR- and IR-spectroscopic and mass spec-
trometric analyses. Its absolute configuration has not
been established so far. Herein, we report a concise
synthesis of (+)-exo-1 for the first time using a
chemoenzymatic approach based on the epoxy alcohol
building block (2R,3R)-3. From the same key interme-
diate, the (+)-antipode of the naturally occurring gib-
berelin synergist (−)-Pestalotin was obtained.
Our synthetic strategy was based on the epoxy alcohol
(2R,3R)-3 as the main chiral building block (Scheme 1).
We envisaged that (2R,3R)-3 could easily be prepared
via a biocatalytic enantioconvergent cascade-reaction
recently developed by us.2 Thus, when cis-configured
( )-halomethyl- or ( )-haloethyl-oxiranes were sub-
jected to the action of a bacterial epoxide hydrolase,
both enantiomers were transformed through opposite
regioselective pathways in an enantioconvergent fash-
* Corresponding author. Tel.: +43-316-380-5332; fax: +43-316-380-
9840; e-mail: kurt.faber@uni-graz.at
Scheme 1. Retrosynthetic analysis.
0957-4166/02/$ - see front matter © 2002 Elsevier Science Ltd. All rights reserved.
PII: S0957-4166(02)00124-6

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S. F. Mayer et al. / Tetrahedron: Asymmetry 13 (2002) 523–528
sequence represents an enzyme-catalyzed cascade-reac-
tion.5 Due to the intrinsic enantioconvergence of the
biohydrolysis, chemical yields were markedly above the
50% limitation set for kinetic resolutions. Such ‘de-
racemization’ processes have recently gained consider-
able attention due to their improved economic
balance.6
lyst with quinoline alone was not sufficient (trans/cis-
ratio 1:5), but required the addition of KOH.
Halogenation of the hydroxyl group of (Z)-5 via Appel
conditions (PPh3/CCl4) gave haloalkene (Z)-6 in 73%
yield.10 Epoxidation of the latter using m-CPBA
afforded ( )-cis-7 in 85% yield. For the identification of
the expected biotransformation product, ( )-threo-8
was independently synthesized as reference material.
cis-Selective dihydroxylation of (Z)-6 with a cat.
amount of OsO4 afforded ( )-threo-diol 8 in 53% yield.
The latter compound was treated with NaH to give
epoxy alcohol ( )-cis-3 after ring-closure in 87% yield.
The synthetic elegance of this process prompted us to
utilize the same building block (2R,3R)-3 for the syn-
thesis of the (+)-antipode of naturally occurring (−)-
Pestalotin, ent-2 (Scheme 1).7 The latter is a gibberelin
synergist isolated from culture filtrate of the phyto-
pathogenic fungus Pestalotia cryptomeriaecola8 and
from an unidentified Penicillium species.9
The racemic substrate ( )-cis-7 was screened for bio-
hydrolysis in Tris-buffer at pH 8.0 using resting cells of
a range of bacteria, in particular Actinomyces sp.,
known to possess strong secondary metabolism and
epoxide hydrolase activity. Under screening conditions
it was verified that in the absence of biocatalyst no
spontaneous hydrolysis of ( )-cis-7 was observed within
the anticipated reaction time of ꢀ130 h. We were
pleased to find that hydrolysis of ( )-cis-7 furnished the
corresponding diol 8, and that the latter intermediate
(detected at low concentration <5%) underwent subse-
quent intramolecular cyclization to yield epoxy alcohol
3 as the final product.
2. Results and discussion
The key substrate for the biocatalytic transformation
catalyzed by bacterial epoxide hydrolases (BEH) was
epoxide ( )-cis-7 (Scheme 2), which was synthesized as
follows: Alcohol 4 was selectively hydrogenated with
Lindlar catalyst to give the corresponding cis-alkene
(Z)-5 in 83% yield (Scheme 2). In order to achieve
absolute cis-selectivity, poisoning of the Lindlar cata-
Scheme 2. Synthesis of substrates and reference materials.
Table 1. Selectivities from the biocatalytic transformation of chloroalkyl-oxirane (9)-cis-7
Entry
Biocatalyst
Substrate e.e.S (%)
Intermediatea e.e.I (%)
Product e.e.P (%) Conversionb (%)
1
2
3
4
5
6
M. paraffinicum NCIMB 10420
Rhodococcus sp. R 312 (CBS 717.73)
Rhodococcus ruber DSM 44540
Rhodococcus ruber DSM 44539
Rhodococcus ruber DSM 43338
Rhodococcus equi IFO 3730
\99 (2R,3R)
50 (2R,3R)
5 (2R,3R)
29 (2R,3R)
12 (2R,3R)
30 (2S,3S)
91 (2S,3R)
67 (2S,3R)
62 (2S,3R)
59 (2S,3R)
69 (2S,3R)
22 (2R,3S)
93 (2R,3R)
72 (2R,3R)
57 (2R,3R)
62 (2R,3R)
64 (2R,3R)
19 (2S,3S)
81c
66d
48d
52d
39d
40d
a Absolute configuration of intermediate was deduced from that of the product based on the SN2-type mechanism of ring closure.2
b Conversion based on non-reacted substrate: c=[sub]−([intermediate]+[product]).
c After 115 h.
d After 130 h.

S. F. Mayer et al. / Tetrahedron: Asymmetry 13 (2002) 523–528
525
Table 1 shows the stereoselectivities [given as conver-
sion (c) and enantiomeric purities of substrate (e.e.S),
intermediate (e.e.I) and product (e.e.P)] obtained from
the biohydrolysis of ( )-cis-7 using various biocatalysts.
In general, ( )-cis-7 was converted with moderate to
good selectivities by several bacterial strains with the
predominant formation of (2R,3R)-3 in up to 93% e.e.
and ]99% d.e. except for Rhodococcus equi IFO 3730,
which produced the mirror-image counterpart (2S,3S)-
3 albeit in low optical purity (entry 6). Several datasets
of c, e.e.S, e.e.I and e.e.P clearly indicated that the
transformation does not follow a kinetic resolution
pathway, which is most striking for entry 1.
was coupled to Grignard-reagent 10.11 This was accom-
plished by treatment of 10 with CuI in THF at −10°C
and subsequent addition of (2R,3R)-9, followed by
deprotection of the silyl ether using Bu4N+F− to furnish
diol (5R,6R)-11 in 59% yield. Finally, Wacker oxida-
tion of (5R,6R)-11 employing PdCl2 as catalyst, using
CuCl2 as re-oxidant, gave (+)-exo-1 in 94% e.e. (16%
overall yield). The absolute configuration of epoxide
(2R,3R)-3 was confirmed by comparison with known
specific rotation values.4 The absolute configuration of
(5R,6R)-11 was deduced from that of the precursor
(2R,3R)-3, since the configuration at carbon centers
C(2) and C(3) of (2R,3R)-3 are not affected during the
coupling reaction. The relative configuration of (+)-
exo-1 was determined via NMR-spectroscopy and its
absolute configuration was deduced from that of pre-
cursor (5R,6R)-11. Thus, (+)-exo-1 was shown to pos-
ses (1R,7R)-configuration.
In order to provide sufficient quantities of (2R,3R)-3
for the asymmetric syntheses of (+)-exo-1 and (+)-
Pestalotin-2, Mycobacterium paraffinicum NCIMB
10420 (1.7 g) was chosen for the preparative-scale bio-
transformation. Thus, conversion of substrate ( )-cis-7
(0.9 g) in Tris-buffer (pH 8.0) gave (2R,3R)-3 in 81%
yield, 99% d.e. and 93% e.e. as the sole product
(Scheme 3). Protection of the free hydroxy moiety in
substrate (2R,3R)-3 with TBDMSCl afforded (2R,3R)-
9 in 91% yield.
For the synthesis of (+)-Pestalotin-2, methyl propiolate
12 was treated with n-BuLi in THF at −78°C and
BF3·Et2O and (2R,3R)-9 were added subsequently.
Deprotection of the silyl ether using Bu4N+F−, which
also initiated lactonization, afforded (+)-Pestalotin-2 in
26% overall yield. The specific rotation of (+)-
Pestalotin-2 was in full accordance with literature
data.12
The remaining steps in the asymmetric syntheses of
(+)-exo-1 and (+)-Pestalotin-2 are depicted in Scheme 4.
In the case of the rum constituent (+)-exo-1, (2R,3R)-9
Scheme 3. Enantioconvergent enzyme-triggered cascade reaction of chloroalkyl-oxirane ( )-cis-7.
Scheme 4. Synthesis of (+)-exo-1 and (+)-Pestalotin-2.

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S. F. Mayer et al. / Tetrahedron: Asymmetry 13 (2002) 523–528
3. Conclusion
obtained from culture collections and strains were
grown as previously described.13
In summary, we have demonstrated that enzyme-trig-
gered cascade reactions represent a valuable tool for the
asymmetric synthesis of natural products. Thus, the
first total synthesis of (+)-exo-7-butyl-5-methyl-6,8-
dioxabicyclo[3.2.1]octane (+)-exo-1, a constituent of
Jamaican rum, as well as (+)-Pestalotin-2 was accom-
plished. Based on the employment of an enantioconver-
gent biocatalytic synthetic strategy using bacterial
epoxide hydrolases, the occurrence of any undesired
stereoisomer was entirely avoided, affording highly
efficient syntheses.
4.2. Syntheses of substrates and reference materials
4.2.1. (Z)-2-Hepten-1-ol (Z)-5. To a solution of alkyne
4 (10 g, 89.3 mmol) in EtOH (70 mL) quinoline (3 mL),
a catalytic amount of KOH and Lindlar catalyst (1.1 g)
were added, and the resulting mixture was vigorously
stirred under H2 for 9 h at atmospheric pressure. The
solids were removed by filtration through a plug of
Celite-545 and the solvent was evaporated. Flash chro-
matography (pentane/MeOAc, 10:1) afforded pure (Z)-
5 as a colorless liquid (8.4 g, 83%). Rf (p.e./EtOAc,
1:1)=0.58, (detection II); spectroscopic data were in
full agreement with those previously reported.4
4. Experimental
4.1. General remarks
4.2.2. (Z)-1-Chloro-2-heptene (Z)-6. Triphenylphos-
phine (16 g, 61.0 mmol) and alcohol (Z)-5 (7.4 g, 65
mmol) were dissolved in CCl4 (50 mL). The reaction
was complete after stirring for 12 h at 80°C. The
solution was concentrated and pentane (50 mL) was
added. The mixture was filtered and the filtrate was
concentrated in vacuo. After flash chromatography
(p.e.) chloroalkene (Z)-6 (6.3 g, 73%) was isolated as a
colorless liquid. Rf (p.e./EtOAc, 10:1)=0.82 (detection
II); spectroscopic data were in full agreement with those
previously reported.4
NMR spectra were recorded in CDCl3 using a Bruker
AMX 360 at 360 (1H) and 90 (13C) MHz and a Bruker
DMX Avance 500 at 500 (1H) and 125 (13C) MHz,
respectively. Chemical shifts are reported relative to
TMS (l 0.00) with CHCl3 as internal standard [l 7.23
(1H) and 76.90 (13C)], coupling constants (J) are given
in Hz.
TLC plates were run on silica gel Merck 60 (F254) and
compounds were visualized by spraying with Mo-
reagent
[(NH4)6Mo7O24·4H2O
(100
g/L),
Ce(SO4)2·4H2O(4 g/L) in H2SO4 (10%)] (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 substances, by Kugelrohr distilla-
tion. Petroleum ether (p.e.) had a boiling range of
60–90°C. GC analyses were carried out on a Varian
3800 gas chromatograph equipped with FID and either
an HP1301 or a HP1701 capillary column (both 30 m,
0.25 mm, 0.25 mm film, N2). Enantiomeric purities were
4.2.3. cis-1-Chloro-2,3-epoxyheptane ( )-cis-7. To a vig-
orously stirred solution of alkene (Z)-6 (4 g, 30.2
mmol) in anhydrous CH2Cl2 (300 mL) finely powdered
NaH2PO4 (ca. 2.5 equiv.) was added. The mixture was
stirred for 15 min at rt, it was cooled to 0°C and
m-CPBA (1.3 equiv.) was added in portions. The mix-
ture was allowed to warm to rt and stirring was contin-
ued for an additional 20 h. The suspension was filtered
and the resulting solution was treated with 10%
aqueous Na2S2O5 (100 mL) to destroy excess peracid.
The resulting two-phase system was stirred for 30 min,
the layers were separated and the organic phase was
washed with satd aqueous NaHCO3 (100 mL), dried
and evaporated. Kugelrohr distillation gave ( )-cis-7 as
a colorless liquid (3.6 g, 85%). Rf (p.e./EtOAc, 10:1)=
analyzed on
a Varian 3800 gas chromatograph
equipped with FID, using a CP-Chirasil-DEX CB
column (25 m, 0.32 mm, 0.25 mm film). H2 was used as
a carrier gas. For programs and retention times vide
infra.
0.50, (detection I); bp20
(Kugelrohr): 95–105°C;
NMR and HRMS datambmaratched those previously
High resolution mass spectra were recorded on a dou-
ble focusing Kratos Profile Mass Spectrometer with
electron impact ionization (EI, +70 eV). Optical rota-
tion values were measured on a Perkin–Elmer polarime-
ter 341 at 589 nm (Na-line) in a 1 dm cuvette and are
given in units of 10−1 deg cm2 g−1.
reported.4
4.2.4. ( )-threo-1-Chloro-2,3-heptanediol ( )-threo-8. To
a solution of alkene (Z)-6 (0.8 g, 6 mmol) in anhydrous
acetone (25 mL) N-methylmorpholine-N-oxide (6.5
mmol) and a catalytic amount of OsO4 were added.
After 3 h solid Na2S2O5 (10 g) was added and the
resulting mixture was stirred for 30 min. Solids were
removed by filtration through a plug of Celite-545 and
the filtrate was washed with sat. aqueous NH4Cl (40
mL). The combined organic phases were dried and
concentrated. Flash chromatography (p.e./EtOAc, 3:1)
gave ( )-threo-8 (0.53 g, 53%). Rf (p.e./EtOAc, 1:1)=
0.46, (detection I); NMR and HRMS data matched
those previously reported.4
Solvents were dried and freshly distilled by common
practice. For anhydrous reactions, flasks were dried at
150°C and flushed with dry argon just before use.
Organic extracts were dried over Na2SO4, and then the
solvent was evaporated under reduced pressure. m-
Chloroperbenzoic acid (m-CPBA, Fluka, 70%) was
used. Compounds 4 and 12 were purchased from Lan-
caster, Lindlar catalyst and Grignard reagent 10 (0.5 M
in THF) from Aldrich. For biotransformations,
lyophilized bacterial cells were used. The bacteria were

S. F. Mayer et al. / Tetrahedron: Asymmetry 13 (2002) 523–528
527
4.2.5. cis-1,2-Epoxy-3-heptanol ( )-cis-3. Diol ( )-threo-
8 (0.15 g, 0.9 mmol) was dissolved in dry THF (10 mL)
and NaH (1.2 mmol) was added. After 30 min water
(10 mL) was added carefully. The solution was
extracted three times with Et2O (20 mL). The combined
organic layers were dried and concentrated. The residue
was purified by flash chromatography (p.e./EtOAc, 5:1)
to afford ( )-cis-3 as a colorless liquid (0.102 g, 87%).
Rf (p.e./EtOAc, 1:1)=0.58, (detection I); NMR and
HRMS data matched those previously reported.4
purified by flash chromatography (p.e./EtOAc, 2:1) to
afford (5R,6R)-11 as a colorless oil (0.13 g, 59%). [h]D20
+24.3 (c 2.7, CHCl3). Rf (p.e./EtOAc, 1:1)=0.65,
1
(detection I); H NMR (360.13 MHz, CDCl3): l=0.89
(3H, t, J=7.1), 1.32–1.58 (10H, m), 2.06 (2H, m), 2.78
(2H, d, J=14.2), 3.36 (2H, s), 4.91–5.02 (2H, m),
5.72–5.84 (1H, m). 13C NMR (90 MHz, CDCl3): l=
14.0, 22.7, 24.9, 27.8, 32.9, 33.2, 33.6, 74.3, 74.5, 114.6,
138.5.
4.2.9. (+)-exo-7-Butyl-5-methyl-6,8-dioxabicyclo[3.2.1]-
octane (+)-exo-1. Diol (5R,6R)-11 (0.11 g, 0.59 mmol)
was dissolved in anhydrous 1,2-dimethoxyethane
(10 mL). The solution was stirred at rt, PdCl2 (0.03 g,
0.17 mmol) and CuCl2 (0.1 g, 0.74 mmol) were added
and stirring was continued for 13 h. The brown solu-
tion was diluted with H2O and Et2O (10 mL each).
After phase separation, the aqueous layer was extracted
twice with Et2O (10 mL). The combined organic phases
were dried (Na2SO4) and concentrated. Flash chro-
matography (pentane/Et2O, 5:1) gave pure (+)-exo-1
(0.073 g, 68%, e.e. 93%). [h]2D0 +51.8 (c 0.65, CHCl3). Rf
4.2.6. (2R,3R)-1,2-Epoxy-3-heptanol (2R,3R)-3 via bio-
transformation. Lyophilized cells of M. paraffinicum
NCIMB 10420 (1.7 g) were rehydrated in Tris-buffer
(50 mL, pH 8.0, 50 mM) for 1 h and epoxide ( )-cis-7
(0.9 g, 6.06 mmol) was added in one portion. The
reaction was monitored by GC on a chiral stationary
phase. After shaking the mixture at 30°C for 115 h, the
reaction was complete and the product was continu-
ously extracted with CH2Cl2 (400 mL) for 24 h. The
organic phase was dried and concentrated and the
residue was purified by flash chromatography (p.e./
EtOAc, 5:1) to give (2R,3R)-3 as a colorless liquid (0.64
g, 81%, e.e.=93%, d.e. ]99%). [h]2D0 −3.2 (c 0.85,
CHCl3). The specific rotation, NMR and HRMS data
are consistent with literature data.4
1
(p.e./EtOAc, 5:1)=0.50, (detection I); H NMR (500.13
MHz, CDCl3): l=0.90 (3H, t, J=6.9), 1.26–1.37 (6H,
m), 1.42 (3H, s), 1.46–1.63 (4H, m), 1.69–1.92 (2H, m),
3.99 (1H, t, J=6.4), 4.13 (1H, s). 13C NMR (90.56
MHz, CDCl3): l=14.0, 17.1, 22.6, 25.1, 27.7, 27.9,
34.9, 35.4, 78.6, 79.8, 107.6. HRMS (C11H20O2): calcd
184,1463 [M+]; found 184.1476 [M+].
4.2.7. (2R,3R)-3-tert-Butyldimethylsilyloxy-1,2-epoxy-
heptane (2R,3R)-9. A solution of alcohol (2R,3R)-3
(0.60 g, 4.6 mmol), TBDMSCl (0.9 g, 5.9 mmol) and
imidazole (0.4 g, 5.9 mmol) in CH2Cl2 (25 mL) was
stirred at rt overnight. The reaction was poured into a
mixture of satd NaHCO3 and CH2Cl2 and stirred vigor-
ously for 30 min. The layers were separated and the
aqueous layer was extracted with CH2Cl2. The com-
bined organic phases were dried and concentrated. The
residue was purified by flash chromatography (p.e.) to
afford (2R,3R)-9 (1.13 g, 91%). [h]2D0 +5.8 (c 1.50,
CHCl3). Rf (p.e./EtOAc, 3:1)=0.9, (detection I); 1H
NMR (360.13 MHz, CDCl3): l=0.08 (3H, s), 0.13 (3H,
s), 0.89 (3H, t, J=7.1), 0.93 (9H, s), 1.24–1.56 (6H, m),
2.57 (1H, dd, J=2.9, 4.9), 2.79 (1H, t, J=4.5), 2.91–
2.94 (1H, m), 3.27 (1H, q, J=6.4). 13C NMR (90 MHz,
CDCl3): l=−5.0, −4.3, 14.0, 18.2, 22.8, 25.9, 27.5, 34.5,
44.9, 56.1, 74.7.
4.2.10. (6R,1%R)-(+)-5,6-Dihydro-6-(1%-hydroxypentyl)-4-
methoxy-pyran-2-one (+)-Pestalotin-2. To a stirred solu-
tion of methyl propiolate 12 (0.27 g, 3.26 mmol) under
Ar in dry THF (10 mL), n-BuLi (1.3 mL of a 2.5 M
solution in hexane, 3.26 mmol) was added at −78°C.
After 15 min, Et2O·BF3 (0.46 g, 3.26 mmol) and a
solution of (2R,3R)-9 (0.4 g, 1.63 mmol) in THF (5
mL) were added dropwise at −78°C. The reaction was
allowed to warm to rt and stirring was continued for
further 12 h. The reaction was quenched by addition of
H2O (30 mL) and Et2O (40 mL). The phases were
separated and the aqueous layer was extracted with
Et2O (2×30 mL). The combined organic phases were
dried and evaporated. The residue was dissolved in
THF (10 mL) and Bu4N+F− (0.73 g, 2.3 mmol) was
added. After 15 min the reaction was quenched by
addition of water (10 mL) and Et2O (20 mL). The
phases were separated and the aqueous layer was
extracted with Et2O (2×20 mL). The combined organic
phases were dried and evaporated. The residue was
purified by flash chromatography (p.e./EtOAc, 1:1) to
afford (+)-Pestalotin-2 as white crystals (0.23 g, 67%).
[h]2D0 +92.5 (c 1.3, MeOH). {In literature: [h]2D0 +91.1 (c
1.34, MeOH)}12 Rf (p.e./EtOAc, 1:2)=0.7 (detection I);
1H NMR (360.13 MHz, CDCl3): l=0.94 (3H, t, J=
6.7), 1.39–1.49 (4H, m), 1.73–1.80 (2H, m), 2.07 (1H, d,
J=4.7), 3.04 (1H, ddd, J=18.6, 5.4, 2.5), 3.52 (1H, d,
J=18.6), 3.66 (3H, s), 4.16–4.21 (1H, m), 4.37–4.41
(1H, m), 5.35 (1H, d, J=1.1).12 13C NMR (125 MHz,
CDCl3): l=13.8, 22.5, 27.6, 27.9, 41.0, 50.6, 69.9, 87.4,
90.2, 169.1, 174.3. HRMS (C11H18O4): calcd 214.1205
[M]+; found 214.1214 [M]+.
4.2.8. (5R,6R)-10-Undecene-5,6-diol (5R,6R)-11. To a
stirred solution of Grignard-reagent 10 (4.6 mL of a 0.5
M solution in THF, 2.3 mmol) under Ar, CuI (0.022 g,
0.115 mmol) was added at −10°C. After 15 min, a
solution of (2R,3R)-9 (0.28 g, 1.15 mmol) in THF (5
mL) was added dropwise at −10°C and the reaction was
stirred for 3 h at rt. The reaction was quenched by
addition of H2O (20 mL) and Et2O (30 mL). The
phases were separated and the aqueous layer was
extracted with Et2O (2×25 mL). The combined organic
phases were dried and evaporated. The residue was
dissolved in THF (10 mL) and Bu4N+F− (0.57 g, 1.8
mmol) was added. After 30 min the reaction was
quenched with water (10 mL) and Et2O (20 mL). The
phases were separated and the aqueous layer was
extracted with Et2O (2×20 mL). The combined organic
phases were dried and evaporated. The residue was

528
S. F. Mayer et al. / Tetrahedron: Asymmetry 13 (2002) 523–528
4.3. General procedure for the screening for biocata-
lytic activity of ( )-cis-7
Acknowledgements
We wish to express our thanks to H. Sterk and K.
Zangger (University of Graz) for skilful assistance in
NMR-spectroscopy. This research was performed
within the Spezialforschungsbereich Biokatalyse (SFB-
A4, project no. F-104) and was financed by the Fonds
zur Fo¨rderung der wissenschaflichen Forschung and the
Austrian Ministry of Science.
Epoxide ( )-cis-7 (5 mL) was hydrolyzed using rehy-
drated lyophilized cells (50 mg) in Tris-buffer (1 mL,
0.05 M, pH 8.0) by shaking the mixture at 30°C with
120 rpm. The reactions were monitored by TLC and
GC. After 130 h the cells were removed by centrifuga-
tion and products were extracted with EtOAc (2×1
mL). The combined organic layers were dried (Na2SO4)
and analyzed.
References
4.4. Chiral analysis
1. ter Heide, R.; Schaap, H.; Wobben, H. J.; de Valois, P.
J.; Timmer, R. In The Quality of Foods and Beverages:
Chemical Technology; Charalambous, G.; Inglett, G.,
Eds.; Academic Press: New York, 1981; Vol. 1, pp.
183–200.
Enantiomeric excesses were analyzed by GC on a chiral
stationary phase (Table 2).
4.5. Determination of absolute configuration
2. Mayer, S. F.; Steinreiber, A.; Orru, R. V. A.; Faber, K.
Tetrahedron: Asymmetry 2001, 12, 41–43.
3. Kroutil, W.; Mischitz, M.; Faber, K. J. Chem. Soc.,
Perkin Trans. 1 1997, 3629–3636.
The absolute configuration of (+)-Pestalotin-2 and
epoxide (2R,3R)-3 was confirmed by comparison with
known specific rotation values.4,12 The determination of
absolute configuration of epoxide 7 and diol 8 was
performed as previously reported.4
4. Mayer, S. F.; Steinreiber, A.; Orru, R. V. A.; Faber, K.
Eur. J. Org. Chem. 2001, 4537–4542.
5. Mayer, S. F.; Kroutil, W.; Faber, K. Chem. Soc. Rev.
2001, 30, 332–339.
6. Faber, K. Chem. Eur. J. 2001, 7, 5005–5010.
7. Mori, K.; Otsuka, T.; Oda, M. Tetrahedron 1984, 40,
2929–2934.
8. Kimura, Y.; Katagiri, K.; Tamura, S. Tetrahedron Lett.
1971, 12, 3137–3140.
The relative configuration of (+)-exo-1 was determined
via NMR spectroscopy. The absolute configuration of
the latter was deduced from that of precursor (5R,6R)-
11, based on a related transformation.14 The absolute
configuration of (5R,6R)-11 was deduced from precur-
sor (2R,3R)-3, since the configuration at the C(2) and
C(3) centers of (2R,3R)-3 remained unchanged during
the coupling reaction.
9. Ellestad, G. A.; McGahren, W. J.; Kunstmann, M. P. J.
Org. Chem. 1972, 37, 2045–2047.
10. Appel, R. Angew. Chem. 1975, 87, 863–874; Angew.
Chem., Int. Ed. Engl. 1975, 14, 801–811.
11. Paddon-Jones, G. C.; McErlean, C. S. P.; Hayer, P.;
Moore, C. J.; Konig, W. A.; Kitching, W. J. Org. Chem.
2001, 66, 7487–7495.
12. Wang, Z.-M.; Shen, M. Tetrahedron: Asymmetry 1997, 8,
3393–3396.
13. Steinreiber, A.; Osprian, I.; Mayer, S. F.; Orru, R. V. A.;
Faber, K. Eur. J. Org. Chem. 2000, 3703–3711.
14. Mayer, S. F.; Mang, H.; Steinreiber, A.; Saf, R.; Faber,
K. Can. J. Chem. 2002, in press.
Table 2. GC-retention times on a chiral stationary phase
Compound
Conditions
Retention time [min]
(configuration)
(9)-exo-1
(9)-cis-3
(9)-cis-7
(9)-threo-8
14 psi, 100°C (iso)
10 psi, 80°C (iso)
10 psi, 80°C (iso)
10 psi, 125°C (iso)
5.4 (−)-exo, 5.6 (+)-exo
14.7 (2S,3S), 16.9 (2R,3R)
9.3 (2S,3S), 9.7 (2R,3R)
9.3 (2R,3S), 10.1 (2S,3R)