Asymmetric reduction of α-thiocyanatoketones by Saccharomyces cerevisiae and Mortierella isabellina-a new route to optically active thiiranes

Article abstract of DOI:10.1016/j.tetasy.2007.04.023

A simple method for the preparation of optically active 1-aryloxy- and 1-arylsulphanyl-3-thiocyanatopropan-2-oles from racemic 1-chloro-3-aryloxy- and 1-chloro-3-arylsulphanyl-2-propanols via 1-aryloxy- and 1-arylsulphanyl-3-thiocyanatopropan-2-ones has been developed. The enantiomerically enriched β-hydroxythiocyanates were obtained by a microbiological reduction of the thiocyanatoketones with Saccharomyces cerevisiae or Mortierella isabellina and subsequently converted into optically active thiiranes on treatment with a lithium hydroxide solution.

Full text of DOI:10.1016/j.tetasy.2007.04.023

Tetrahedron: Asymmetry 18 (2007) 1202–1209
Asymmetric reduction of a-thiocyanatoketones
by Saccharomyces cerevisiae and Mortierella isabellina—a
new route to optically active thiiranes
Edyta Łukowska and Jan Plenkiewicz*
Faculty of Chemistry, Warsaw University of Technology, Noakowskiego 3, 00-664 Warsaw, Poland
Received 5 April 2007; accepted 20 April 2007
Abstract—A simple method for the preparation of optically active 1-aryloxy- and 1-arylsulphanyl-3-thiocyanatopropan-2-oles from race-
mic 1-chloro-3-aryloxy- and 1-chloro-3-arylsulphanyl-2-propanols via 1-aryloxy- and 1-arylsulphanyl-3-thiocyanatopropan-2-ones has
been developed. The enantiomerically enriched b-hydroxythiocyanates were obtained by a microbiological reduction of the thiocyana-
toketones with Saccharomyces cerevisiae or Mortierella isabellina and subsequently converted into optically active thiiranes on treatment
with a lithium hydroxide solution.
ꢀ 2007 Elsevier Ltd. All rights reserved.
1. Introduction
which can be used as anesthetics, analgesics or chiral aux-
iliaries in asymmetric synthesis.8,9
The asymmetric reduction of the carbonyl group in
b-substituted ketones is often catalyzed by baker’s yeast.
The broad scope of this biotransformation, its preparative
simplicity, and usually good stereochemical results arising
from precise facial recognition and high substrate tolerance
of the yeast dehydrogenases, are the reasons for its com-
mon usage. Depending on the b-substituent, the ketone
molecule can be reduced to a diol1,2 or to an appropriately
substituted secondary alcohol.3 Some of these compounds
found application as useful building blocks in the synthesis
of various biologically active compounds. For example, the
enantiomerically pure 1-substituted 3-aryloxypropan-2-ols
are used as convenient intermediates in the preparation
of drugs, such as b-receptor blockers,4 or of chiral frag-
ments in the optically active crown ethers.1 1-Azido-3-aryl-
oxy-2-propanols are direct precursors of aziridines4 and 1-
amino-3-aryloxy-2-propanols,4 the popular b-adrenolytic
drugs commonly used in the treatment of hypertension
and other circulatory disorders.5 Baker’s yeast dehydrogen-
ases are also known to reduce some phthalimide6- or oxy-
phthalimide7- substituted ketones with the formation of the
corresponding amino- or oxyaminoalcohol derivatives,
From the point of view of synthetic chemistry b-hydroxy-
thiocyanates, known as intermediates in thiirane synthesis,
constitute as another interesting subclass of secondary
alcohols. There are two known synthetic methods for
preparing these alcohols: in the first, cyclic sulfates can
be reacted with ammonium thiocyanate,10 while the second
method consists of the opening of oxiranes with thiocya-
nate anion in the presence of different catalysts, such as
titanium isopropoxide,11 triphenylphosphine thiocyanogen
(TPPT),12 titanium and zinc chlorides,13 triphenylphos-
phine palladium,14 crown ethers,15 Selectfluor16 or tetra-
arylporphyrins.17 However, all of these methods to date
have only been used for the preparation of racemic
b-hydroxythiocyanates.
Recently,18,19 we described a chemo-enzymatic procedure
for the preparation of some enantiomerically enriched 1-
substituted-3-thiocyanatopropan-2-ols and their acetates.
These compounds appeared to be good substrates in the
synthesis of optically active 2-(arylsulphanylmethyl)- and
2-(aryloxymethyl)thiiranes.19
Herein we report another method for the preparation of
optically active b-hydroxythiocyanates, which consists of
the synthesis of appropriate a-thiocyanatoketones and
their stereoselective reduction by yeast (Saccharomyces
*
Corresponding author. Tel.: +48 22 660 75 70; fax: +48 22 628 27 41;
e-mail: plenki@ch.pw.edu.pl
0957-4166/$ - see front matter ꢀ 2007 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tetasy.2007.04.023

E. Łukowska, J. Plenkiewicz / Tetrahedron: Asymmetry 18 (2007) 1202–1209
1203
H2O,
Ar
Ar
NaOH
H2O
HCl
CrO3,H2SO4
CH3COCH3
ArOH
+
O
Cl
O
Cl
O
O
Cl
Ar
O
O
OH
1a-e
2a-e
a-Ar = Ph-
b-Ar = p-Cl-Ph-
c-Ar = p-CH3-Ph-
d-Ar = o-Cl-Ph-
e-Ar = o-CH3-Ph-
Ar
Ar
KSCN
EtOH
O
SCN
O
Cl
O
O
2a-e
3a-e
Scheme 1.
cerevisiae) and fungi (Mortierella isabellina) dehydro-
genases.
complicated mixture of the reaction products; 4a was not
stable enough to stand the reaction conditions. In an
attempt to increase the yield of 5a, the crude mixture of
products was treated with lithium hydroxide in a two-phase
aqueous LiOH/THF system, which is known in converting
b-hydroxythiocyanates in high efficiency into thiiranes19
(Scheme 2). However, as can be seen in Table 2, the yields
of thiiranes obtained in this way were similar to those
noted in the non-catalyzed decomposition of b-thiocyanato
alcohols.
2. Results and discussion
The starting glycidyl ethers were prepared in the William-
son reaction from the appropriate phenols and epichloro-
hydrin in an aqueous 10% sodium hydroxide solution. In
our experiments the oxirane intermediates were not iso-
lated; upon addition of an excess amount of hydrochloric
acid the reaction mixture was stirred at room temperature
for some time with TLC monitoring (Scheme 1) to give
1-chloro-3-aryloxypropan-2-ols 1a–e. The yields of the
reaction depended on the phenyl-ring substituent and
usually ranged between 69% and 86%. Alcohols 1a–e were
oxidized to the corresponding 1-chloro-3-aryloxypropan-
2-ones 2a–e in the reaction with the Jones’ reagent in an
acetone solution at 5 ꢁC. The yields of ketones 2a–e are
summarized in Table 1. Conversion of 2a–e into the corre-
sponding 1-aryloxy-3-thiocyanatopropan-2-ones 3a–e was
accomplished in good yields (Table 1) by refluxing with
potassium thiocyanate in an ethanol solution.
Table 2. The yields and ee (%) of (R)-thiirane 5a obtained in reaction
witha or without LiOH/THF system
Entry
Yeast g/1 mmol of
substrate
Incubation
time (h)
ee (%)
Yield of 5a
1
2
3a
4a
3
3
3
2.5
21
48
21
24
82
88
77
88
13
38
15
30
a Reactions with LiOH/THF.
In order to avoid the laborious and time consuming extrac-
tion procedure and hoping to increase the yield of thiirane,
we next investigated the microbiological reduction of 3a in
an organic solvent. Hexane, the solvent of choice in reac-
tions with living cells, failed to dissolve 3a. For the same
reason, other highly non-polar solvents also proved unsuit-
able. Thus, tert-butyl methyl ether was chosen for the pre-
liminary experiments. In a saturated solution (24 mL of the
ether/1 mmol of 3a), no reduction of the carbonyl group
took place and the addition of a trace amount of water
was necessary.
Table 1. The yields of ketones 2a–e and 3a–e
Entry
Ar
Yield of 2a–e (%)
Yield of 3a–e (%)
a
b
c
d
e
Ph–
44.5
86
43
53
41
70
72
81.5
69
p-Cl–Ph–
p-CH3–Ph–
o-Cl–Ph–
o-CH3–Ph–
75
Our first experiments with the baker’s yeast-catalyzed
reduction of prochiral 3a–e were carried out with 3a added
in a DMF solution to the growing yeast cultures (30 ꢁC)
suspended in an aqueous, glucose supplemented medium.
Upon removal of the biomass and routine extraction with
ethyl acetate only some 2-(phenoxymethyl)thiirane 5a
could be isolated by column chromatography from the
As shown in Table 3, the amount of yeast also affects the
thiirane yield. A quantitative conversion of 1 mmol of 3a
into 5a required at least 2 g of the yeast, but with 2.5 g,
the reaction was twice as fast. Further increase in the
amount of yeast did not accelerate the reaction, but de-
creased the product yield. Alcohol 4a was probably more
THF, LiOH
SCN
Ar
Ar
Baker's yeast
Solvent
O
SCN
O
O
S
H2O
Ar
(R)-(+)-5a-e
O
OH
3a-e
(S)-4a-e
Scheme 2.

1204
E. Łukowska, J. Plenkiewicz / Tetrahedron: Asymmetry 18 (2007) 1202–1209
Table 3. The yields of thiirane (R)-(+)-5a obtained in reaction catalyzed
by different amounts of baker’s yeast in t-BuOMe
1-Arylsulphanyl-3-thiocyanatopropan-2-ones 7a–c are
another group of a-thiocyanatoketones used by us in the
synthesis of optically active thiiranes. They were prepared
from 6a–c by the chloride!thiocyanate exchange reaction
(Scheme 3). Ketones 6a–c were obtained by a known pro-
cedure20 from the corresponding sodium benzenethiolates
(prepared from benzenethiol and sodium hydroxide in an
aqueous medium) and dichloroacetone in a methanol solu-
tion. The yields of 3-chloro- and 3-thiocyanatopropan-2-
ones are summarized in Table 6.
Yeast g/1 mmol Time (h) ee (%)
of substrate
c (%)
Thiirane 5a
yield (%)
1
2
2.5
3
168
45
24
93
93
93
93
Small conversion Not isolated
100
100
100
79
77
72
20
strongly adsorbed by yeast than the starting ketone 3a.
Due to its instability, 4a was not isolated but in situ con-
verted into 5a in the LiOH/THF system. Therefore, the
progress of the 3a!4a was monitored by observation of
the disappearence of 3a spot on TLC plates.
The yeast-catalyzed reductions of 1-arylsulphanyl-3-thio-
cyanatopropan-2-ones 7a–c (Scheme 4) were performed
under the conditions which secured the best yields and
selectivities with 3a–e. The reactions were arrested after
24 h and the crude (S)-alcohols were converted into the
corresponding (R)-thiiranes as described earlier. However,
7a–c were reduced with substantially lower stereoselectivi-
ties (ee = 55–80%) than those noted with 3a–e. Detailed
results are shown in Table 7.
Three other organic solvents, diethyl ether, toluene and
tetrahydrofuran, were investigated in the reaction besides
tert-butyl methyl ether. The data in Table 4 reveal that only
THF was completely unsuitable; it caused a total inhibition
of the reaction. The other solvents gave fairly good results
of a similar order.
The bioreductions of 3a–c were also carried out with living
cells of M. isabellina DSM 1414 (Mi) in a 2% glucose solu-
tion at 30 ꢁC (Scheme 5). Incubation of 3a–c with a sus-
pended culture of the fungi, and subsequent treatment
with THF/LiOH (as previously described) gave the corre-
sponding (S)-thiiranes 5a–c as the major products in 20–
57% isolated yields. Attempted separations of (R)-alcohols
4a–c were unsuccessful because of their low stability.
Detailed information with regards to the reactions is
presented in Table 8. As can be seen, the enantiomeric
excesses (ee%) and yields of 5a–c prepared with M. isabel-
lina were much lower than those obtained with baker’s
yeast.
Bioreductions of 3b–e followed by transformations into
thiiranes 5b–e were performed under the optimal condi-
tions developed with 3a (1 mmol of the ketone, 24 mL of
tert-butyl-methyl ether, 2.5 g of yeast, Scheme 2). The
results of these experiments are summarized in Table 5.
High enantiomeric excesses of thiiranes 5a–e obtained in
satisfactory yields makes the method of preparative
interest.
Table 4. Solvent effect in reduction of 3a catalyzed by baker’s yeast
The absolute configurations of thiiranes 5a–e and 9a–c
were determined by comparing their specific rotations with
those described earlier.19 They indicated an opposite
Solvent
Baker’s
yeast (g)
Time
(h)
ee
(%)
Thiirane 5a
yield (%)
H2O
TBME
2.5
2.5
24
24
88
93
30
77
Et2O
Et2O
2.5
3
24
21
88.6
66
60
Table 6. The yields of ketones 6a–c and 7a–c
Compound Ar
Yield of 6a–c (%) Yield of 7a–c (%)
Toluene
Toluene
2.5
3
24
21
92
67.5
66
a
b
c
Ph–
p-Cl–Ph–
p-CH3–Ph–
89
61
46
38
39
37
THF
2.5
—
Table 5. The yields and enantiomeric excesses of thiiranes 5a–e
Table 7. Reduction of ketones 7a–c catalyzed by baker’s yeast in t-
BuOMe
Compound
Time (h)
ee (%)
Yield (%)
5a
5b
5c
5d
5e
24
24
24
24
24
93
99
92
95
96
77
86.5
79
76
91
Substrate
Time (h)
ee (%)
Yield (%)
7a
7b
7c
24
24
24
55
80
56
73
62.5
80
NaOH, H2O
MeOH
Ar
Ar
KSCN
EtOH
ArSH
+
ClCH2COCH2Cl
S
SCN
S
Cl
O
O
7a-c
6a-c
Scheme 3.

E. Łukowska, J. Plenkiewicz / Tetrahedron: Asymmetry 18 (2007) 1202–1209
1205
THF, LiOH
H2O
Ar
Ar
Baker's yeast
S
SCN
S
SCN
S
S
Ar
t-BuOMe, H2O
O
OH
7a-c
(S)-8a-c
(R)-(-)-9a-c
Scheme 4.
Ar
Ar
O
Whole cells
THF, LiOH
H2O
O
3a-c
SCN
SCN
O
S
Ar
M. isabellina DSM 1414
O
OH
(R)-4a-c
(S)-(-)-5a-c
Scheme 5.
Table 8. Yields and enantiomeric purities of (S)-thiiranes 5a–c obtained
by bioreduction of 3a–c by Mortierella isabellina DSM 1414 (Mi)
4. Experimental
4.1. General
Substrate Ar
Incubation c (%)
ee
Yield
time (h)
(%) (%)
1H (400 MHz) and 13C NMR (100 MHz) spectra were
recorded on a Varian Mercury 400 MHz spectrometer in
a CDCl3 solution; IR spectra were taken on a Carl Zeiss
Specord M80 instrument. Ees of the thiiranes 5a–e were
determined on a Thermo–Separation Products P-100
HPLC apparatus with Chiralcel OD-H column (in hex-
ane:iso-propanol 95:5; 98:2, 99:1 0,8 mL/min) using the
corresponding racemic compounds as references. Ees of
the thiiranes 9a–c were determined by chiral gas chroma-
tography (Agilent Technologies 6890N, 30 m-long Cyclo-
dex B (Agilent Technologies) capillary column). Optical
rotations were measured in a CDCl3 solution with a Po-
lAAr 32 polarimeter. Elemental analyses were performed
on a CHNSCl/O Perkin–Elmer type 2400 instrument.
The reactions were monitored by TLC on silica gel 60
(230–400 mesh) and by GC with Hewlett-Packard Model
5890 II chromatograph with Helium as the carrier gas.
3a
3b
3c
3c
Ph–
p-Cl–Ph–
p-CH3–Ph–
24
168
48
100
100
27
13
57
20
21
38
Low conversion 30
100
p-CH3–Ph– 168
stereopreference of baker’s yeast and M. isabellina in the
reduction of 1-aryloxy-3-thiocyanatopropan-2-ones. On
the basis of the reaction mechanism proposed by Price
and Kirk21 for the transformation of b-thiocyanatoalco-
hols into thiiranes, it seems reasonable to assume that the
configuration of the optically active alcohols 4a–e and
8a–c is opposite to that of the final thiiranes. In all reduc-
tions catalyzed by baker’s yeast, an (S)-stereopreference of
the resulting alcohol was observed. This is in agreement
with Prelog’s rule of stereocontrol observed in most baker’s
yeast reductions with Re-face22 addition of a hydride
anion. On the contrary, alcohols 4a–c prepared by
reductions with M. isabellina DSM 1414 (Mi) possess the
opposite specific rotation, which suggests an anti-Prelog
stereopreference.
4.2. Microorganisms
The instant dry S. cerevisiae yeast was generously supplied
by Mauri Foods Ltd. The DSM 1414 strain of M. isabellina
was purchased from German Collection of Microorgan-
isms and Cell Cultures (DSMZ).
3. Conclusions
The baker’s yeast-induced asymmetric reduction of a-thio-
cyanatoketones was found to be a useful method for the
preparation of the corresponding optically active b-
hydroxythiocyanatopropane derivatives. In organic sol-
vents, this transformation occurred with high stereoselec-
tivity. The enantiomeric purities of the alcohols obtained
were higher in the reductions of 1-aryloxy-3-thiocyanato-
propan-2-ones than of 1-arylsulphanyl-3-thiocyanatopro-
pan-2-ones. The transformations of the crude optically
active b-hydroxythiocyanatopropane derivatives into the
corresponding enantiomerically enriched thiiranes were
carried out in a two-phase aqueous LiOH/THF system
with Walden inversion and preservation of stereoselectiv-
ity. An opposite stereopreference of the baker’s yeast and
M. isabellina was observed in the reduction of 1-aryloxy-
3-thiocyanatopropan-2-ones.
4.3. Growth medium for M. isabellina
Malt extract (30 g) and soya peptone (3 g), were dissolved
in 1 L of distilled water and the pH adjusted to 5.6. The
liquid medium was sterilized at 120 ꢁC for 15 min. The
solid medium was prepared by adding 7.5 g of agar–agar
to 500 ml of the liquid medium and sterilization was carried
out under the same conditions. The microorganism was
grown on a plate with agar medium for 3 days at 27 ꢁC
until it was well sporulated. Spores from the surface culture
were used to inoculate flasks containing sterile liquid med-
ium, next incubated at 30 ꢁC for 3 days on a rotary shaker
at 140 rpm. Then the fungal mycelium was collected by
filtration from the growing culture.

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E. Łukowska, J. Plenkiewicz / Tetrahedron: Asymmetry 18 (2007) 1202–1209
4.4. General procedure for the synthesis of 1-chloro-3-
aryloxypropan-2-one 2a–e
of 1,3-dichloropropan-2-one (6.35 g, 0.05 mol) in metha-
nol–water (1:3) mixture (50 mL) at 0 ꢁC. The mixture was
stirred at 0 ꢁC for 7 h and then at room temperature for
the next 10 h. The precipitated product was extracted with
chloroform and the extract was washed with water, dried
over Na2SO4 and evaporated to dryness. The solid residue
of 6a was recrystallized from Et2O. The remaining crude
products 6b–c were purified by chromatography on a
silica-gel column with n-hexane–ethyl acetate (10:1 v/v)
To a stirred solution of 1-chloro-3-aryloxypropan-2-ol
1a–e (0.053 mol) in CH3COCH3 (116 mL) at 5 ꢁC, a solu-
tion of H2CrO3 (prepared from H2SO4 (6.16 mL), CrO3
(7.71 g) and H2O (14 mL) was added dropwise over 2 h.
Next the mixture was stirred for 1hr at room temperature
and stopped by the dropwise addition of 2-propanol
(16 mL). The inorganic precipitate was then filtered off
and washed with CH3COCH3 (2 · 60 mL). The solvent
was evaporated and to the resulting crude product H2O
(70 mL) was added. The mixture was extracted with CHCl3
(3 · 60 mL) and the organic layer washed with water
(3 · 50 mL), dried over anhydrous Na2SO4 and evapo-
rated. Product was purified by chromatography on silica-
gel column with n-hexane–dichloromethane (1:4 v/v) as
1
as the eluent. H, 13C NMR spectra and IR data of the
prepared ketones are reported below:
4.5.1. 1-Chloro-3-phenylsulphanylpropan-2-one 6a. Col-
1
ourless crystals; mp 43–44 ꢁC (lit.27 46–47 ꢁC). H NMR
(CDCl3): d ppm: 3.83 (s, 2H (CH2SPh)); 4.27 (s, 2H
(CH2Cl)); 7.22–7.37 (m, 5H (Ph)). 13C NMR (CDCl3); d
ppm; 41.22; 46.46; 127.48; 129.27; 129.28; 130.13; 197.13.
IR (Nujol, cmꢀ1) 1728 (mCO).
1
the eluent. H, 13C spectra and IR data of the prepared
ketones are reported below:
4.5.2. 1-Chloro-3-(4-chlorophenylsulphanyl)propan-2-one 6b.
Colourless crystals; mp 39–41 ꢁC. 1H NMR (CDCl3): d
ppm: 3.82 (s, 2H (CH2SPh)); 4.25 (s, 2H (CH2Cl)); 7.26–
7.28 (m, 4H (Ph)). 13C NMR (CDCl3); d ppm; 41.27;
46.30; 129.47; 131.67; 132.01; 133.77; 196.84. IR (Nujol,
cmꢀ1) 1720 (mCO). Anal. Calcd for C9H8Cl2OS: C, 45.97;
H, 3.43; Cl, 30.16; S, 13.64. Found: C, 45.89; H, 3.38; Cl;
30.01; S, 13.79.
1
4.4.1. 1-Chloro-3-phenoxypropan-2-one 2a. Oil. H NMR
(CDCl3): d ppm: 4.43 (s, 2H (CH2Cl)); 4.76 (s, 2H
(CH2OPh)); 6.89–7.34 (m, 5H (Ph)). 13C NMR (CDCl3);
d ppm; 46.81; 71.53; 114.41; 122.18; 129.81; 157.23;
199.06. IR (film, cmꢀ1) 1735 (mCO). H NMR spectrum is
1
identical with that given in the lit.23
4.4.2. 1-Chloro-3-(4-chlorophenoxy)propan-2-one 2b. Col-
1
ourless crystals: mp 70–72 ꢁC (lit.24 63–66 ꢁC). H NMR
1
4.5.3. 1-Chloro-3-(tolylsulphanyl)propan-2-one 6c. Oil. H
(CDCl3): d ppm: 4.38 (s, 2H (CH2Cl)); 4.76 (s, 2H
(CH2OPh)); 6.82–7.29 (m, 4H (Ph)). 13C NMR (CDCl3);
d ppm; 46.45; 71.66; 115.83; 127.22; 129.70; 155.90;
198.39. IR (Nujol, cmꢀ1) 1740 (mCO).
NMR (CDCl3): d ppm: 2.31 (s, 3H, (CH3)); 3.77 (s, 2H
(CH2SPh)); 4.27 (s, 2H (CH2Cl)); 7.10–7.28 (m, 4H (Ph)).
13C NMR (CDCl3) d ppm; 21.01; 41.85; 46.49; 129.64;
130.07; 131.03; 137.94; 197.12. IR (Nujol, cmꢀ1) 1730
(mCO).
4.4.3. 1-Chloro-3-(p-tolyloxy)propan-2-one 2c. Colourless
1
crystals; mp 50–52 ꢁC (lit.25 59 ꢁC). H NMR (CDCl3): d
4.6. General procedure of thiocyanatoketones 3a–e and
7a–c preparation
ppm: 2.30 (s, 3H (CH3)); 4.42 (s, 2H (CH2Cl)); 4.72 (s,
2H (CH2OPh)); 6.78–7.12 (m, 4H (Ph)). 13C NMR
(CDCl3); d ppm; 20.42; 46.85; 71.75; 114.23; 130.20;
131.52; 155.16; 199.29. IR (Nujol, cmꢀ1) 1745 (mCO).
A mixture of the appropriate 1-chloro-3-aryloxypropan-2-
one 2a–e (or 1-chloro-3-arylsulphanylpropan-2-one 6a–c)
(10 mmol), potassium thiocyanate (10 mmol), and ethanol
(41 mL) was stirred under reflux conditions. The progress
of the reaction was monitored by TLC, using n-hexane–
ethyl acetate (3:1 v/v) as the eluent. After completion of
the reaction, an equal volume of water was added and
the resulting precipitate was filtered off, or exacted with
CH2Cl2. Products 3a and 3b were purified by crystalliza-
tion from EtOH, 3c–e from Et2O whilst ketones 7a–c were
purified by chromatography on silica-gel column with n-
hexane–ethyl acetate (10:1 v/v) as the eluent. 1H, 13C
NMR spectra, IR data, and elemental analyses of the
ketones prepared are reported below:
4.4.4. 1-Chloro-3-(2-chlorophenoxy)propan-2-one 2d. Col-
ourless crystals; mp 51.5–53 ꢁC 1H NMR (CDCl3): d
ppm: 4.57 (s, 2H (CH2Cl)); 4.77 (s, 2H (CH2OPh)); 6.82–
7.42 (m, 4H (Ph)). 13C NMR (CDCl3); d ppm; 47.16;
72.44; 113.50; 123.02; 123.15; 127.93; 130.69; 152.84;
198.37. IR (Nujol, cmꢀ1) 1741 (mCO).
4.4.5. 1-Chloro-3-(o-tolyloxy)propan-2-one 2e. Colourless
1
crystals; mp 46.5–49 ꢁC (lit.26 50 ꢁC). H NMR (CDCl3):
d ppm: 2.27 (s, 3H (CH3)); 4.42 (s, 2H (CH2Cl)); 4.77 (s,
2H (CH2OPh)); 6.60–7.05 (m, 4H (Ph)). 13C NMR
(CDCl3); d ppm; 15.42; 47.18; 75.31; 113.51; 123.04;
123.17; 127.95; 130.72; 152.86; 198.40. IR (Nujol, cmꢀ1
)
1740 (mCO).
4.6.1. 1-Phenoxy-3-thiocyanatopropan-2-one 3a. Colour-
less crystals; mp 65–66 ꢁC. 1H NMR (CDCl3): d ppm:
4.28 (s, 2H (CH2SCN)); 4.69 (s, 2H (CH2OPh)); 6.89–
7.36 (m, 5H (Ph)). 13C NMR (CDCl3); d ppm; 41.59;
71.93; 110.98; 114.34; 122.52; 129.97; 156.87; 199.27. IR
(Nujol, cmꢀ1) 2150 (mCN); 1740 (mCO). Anal. Calcd for
C10H9NO2S: C, 57.95; H, 4.38; N, 6.76; S, 15.47. Found:
C, 57.84; H, 4.40; N, 6.71; S, 15.44.
4.5. General procedure of the synthesis of 1-chloro-3-
arylsulphnylpropan-2-ones 6a–c
A suspension of sodium benzenethiolate prepared from
benzenethiol (5.5 g, 0.05 mol) and sodium hydroxide (2 g,
0.05 mol) in water (50 mL) was added to a stirred solution

E. Łukowska, J. Plenkiewicz / Tetrahedron: Asymmetry 18 (2007) 1202–1209
1207
4.6.2. 1-(4-Chlorophenoxy)-3-thiocyanatopropan-2-one 3b.
Colourless crystals; mp 89–90 ꢁC. 1H NMR (CDCl3): d
ppm: 4.25 (s, 2H (CH2SCN)); 4.66 (s, 2H (CH2OPh));
6.82–7.30 (m, 4H (Ph)). 13C NMR (CDCl3); d ppm;
41.32; 72.09; 110.90; 115.70; 127.48; 129.81; 155.44;
198.48. IR (Nujol, cmꢀ1) 2155 (mCN); 1745 (mCO). Anal.
Calcd for C10H8NClO2S: C, 49.69; H, 3.34; N, 5.80; Cl,
14.67; S, 13.27. Found: C, 49.80; H, 3.70; N, 5.83; Cl,
14.37; S, 12.99.
(CDCl3); d ppm; 21.07; 41.73; 43.28; 111.07; 129.00;
130.33; 131.15; 138.45; 196.31. IR (Nujol, cmꢀ1) 2140
(mCN); 1705 (mCO). Anal. Calcd for C11H11NOS2: C,
55.67; H, 4.67; N, 5.90; S, 27.02. Found: C, 55.71; H,
4.71; N, 5.93; S, 27.11.
4.7. General procedure for the synthesis of optically active
thiiranes
In a typical experiment, the appropriate ketone 3a–e or
7a–c (1 mmol) was dissolved in 24 mL of tert-butyl methyl
ether and 2.5 g of Mauripan baker’s yeast and 1.5 mL of
H2O was added. The mixture was shaken at room temper-
ature and the conversion monitored by TLC with n-hex-
ane:ethyl acetate (3:1 v/v) as the eluent. After 24 h, the
reaction was stopped by filtering off the baker’s yeast and
the solvent was evaporated. The resulting crude optically
active b-hydroxythiocyanate was used as the substrate in
the thiirane synthesis. Each of the optically active
b-hydroxythiocyanates 4a–e was dissolved in 14 mL of
THF and a solution of LiOHÆH2O (2 mmol) in 2.5 mL of
H2O was added. For compounds 7a–c b-hydroxythiocya-
nates 8a–c were dissolved in 28 mL of THF and a solution
of LiOHÆH2O (4 mmol) in 5 mL H2O was added. The mix-
ture was stirred at room temperature and the progress of
the reaction monitored by TLC using n-hexane:ethyl ace-
tate (3:1 v/v) as the eluent. After completion of the reaction
(about 2 h), the organic layer was separated and the solvent
evaporated. The crude product was purified by chromato-
graphy on a short silica-gel column with n-hexane:ethyl
acetate (7:1 v/v for elution of thiiranes 5a–e and 15:1 for
4.6.3. 1-Thiocyanato-3-(p-tolyloxy)propan-2-one 3c. Col-
ourless crystals; mp 70–71 ꢁC. H NMR (CDCl3): d ppm:
1
2.30 (s, 3H (CH3)); 4.26 (s, 2H (CH2SCN)); 4.65 (s, 2H
(CH2OPh)); 6.78–7.14 (m, 4H (Ph)). 13C NMR (CDCl3);
d ppm; 20.43; 41.58; 72.13; 111.01; 114.17; 130.35; 131.91;
154.83; 199.53. IR (Nujol, cmꢀ1) 2160 (mCN); 1745 (mCO).
Anal. Calcd for C11H11NO2S: C, 59.71; H, 5.01; N, 6.33;
S, 14.49. Found: C, 59.53; H, 5.02; N, 6.30; S, 14.70.
4.6.4. 1-(2-Chlorophenoxy)-3-thiocyanatopropan-2-one 3d.
1
Colourless crystals; mp 84.5–85.5 ꢁC. H NMR (CDCl3):
d ppm: 4.36 (s, 2H (CH2SCN)); 4.71 (s, 2H (CH2OPh));
6.84–7.43 (m, 4H (Ph)). 13C NMR (CDCl3); d ppm;
41.34; 72.62; 110.89; 113.56; 123.09; 123.32; 128.06;
130.75; 152.52; 198.38. IR (Nujol, cmꢀ1) 2158 (mCN); 1740
(mCO). Anal. Calcd for C10H8NClO2S: C, 49.69; H, 3.34;
N, 5.80; Cl, 14.67; S, 13.27. Found: C, 49.53; H, 3.59; N,
5.73; Cl, 14.43; S, 13.24.
4.6.5. 1-Thiocyanato-3-(o-tolyloxy)propan-2-one 3e. Col-
ourless crystals; mp 71.5–72.5 ꢁC. 1H NMR (CDCl3): d
ppm: 2.30 (s, 3H (CH3)); 4.29 (s, 2H (CH2SCN)); 4.68 (s,
2H (CH2OPh)); 6.68–7.21 (m, 4H (Ph)). 13C NMR
(CDCl3); d ppm; 16.29; 41.58; 71.96; 110.56; 110.97;
122.15; 126.64; 127.13; 131.36; 155.02; 199.28. IR (Nujol,
1
thiiranes 9a–c). H, 13C NMR spectra, optical rotations
and elemental analyses of the prepared thiiranes 5a–e and
9a–c are reported below:
cmꢀ1
)
2162 (mCN); 1745 (mCO). Anal. Calcd for
4.7.1. (R)-(+)-2-(Phenoxymethyl)thiirane 5a. Oil, yield
72%. 1H NMR (CDCl3) d ppm: 2.32–2.62 (m; 2H
(CHCH2S)); 3.28 (m; 1H (CH)); 3.90 (dd; 1H
(OCHaHbCH); JHaCH = 7.2 Hz; JHaHb = 10 Hz); 4.22
(dd; 1H (OCHaHbCH); JHbCH = 5.2 Hz); 6.90–7.31
C11H11NO2S: C, 59.71; H, 5.01; N, 6.33; S, 14.49. Found:
C, 59.80; H, 5.03; N, 6.31; S, 14.52.
4.6.6. 1-(Phenylsulphanyl)-3-thiocyanatopropan-2-one 7a.
1
Colourless crystals; mp 66.5–67.5 ꢁC. H NMR (CDCl3):
(m; 5H (Ph)). 13C NMR (CDCl3) d ppm: 23.98; 31.37;
d ppm: 3.78 (s, 2H (CH2SPh)); 4.17 (s, 2H (CH2SCN));
7.26–7.36 (m, 5H (Ph)). 13C NMR (CDCl3); d ppm;
41.62; 42.62; 111.01; 127.88; 129.52; 130.25; 132.85;
196.31. IR (Nujol, cmꢀ1) 2150 (mCN); 1725 (mCO). Anal.
Calcd for C10H9NOS2: C, 53.79; H, 4.06; N, 6.27; S,
28.72. Found: C, 54.01; H, 4.36; N, 6.14; S, 28.67.
20:5
72.51; 114.63; 121.21; 129.53; 158.35. ½aꢁD ¼ þ16:5 (c 2,
1
CHCl3) ee = 93%. H NMR and 13C NMR spectra are
identical with those given in the lit.18
4.7.2. (R)-(+)-2-((4-Chlorophenoxy)methyl)thiirane 5b. Oil,
1
yield 76%. H NMR (CDCl3) d ppm: 2.31–2.61 (m; 2H
(CHCH2S)); 3.25 (m; 1H (OCH2CHCH2)); 3.87–4.16 (m;
2H (OCH2CH)); 6.82–7.24 (m; 4H (Ph)). 13C NMR
(CDCl3) d ppm: 24.01; 31.40; 72.62; 114.92; 126.59;
129.50; 156.45. ½aꢁD ¼ þ11:4 (c 2.89 CHCl3) ee = 95%. H
NMR and 13C NMR spectra are identical with those given
in the lit.18
4.6.7. 1-(4-Chlorophenylsulphanyl)-3-thiocyanatopropan-2-
one 7b. Colourless crystals; mp 59–61 ꢁC. 1H NMR
(CDCl3): d ppm: 3.76 (s, 2H (CH2SPh)); 4.17 (s, 2H
(CH2SCN)); 7.27–7.32 (m, 4H (Ph)). 13C NMR (CDCl3);
d ppm; 41.45; 42.73; 110.85; 129.72; 131.21; 131.83;
134.28; 195.76. IR (Nujol, cmꢀ1) 2130 (mCN); 1715 (mCO).
Anal. Calcd for C10H8NClOS2: C, 46.60; H, 3.13; N,
5.43; Cl, 13.75; S, 24.88. Found: C, 46.65; H, 3.35; N,
5.40; S, 24.83.
24
1
4.7.3. (R)-(+)-2-(p-Tolyloxymethyl)thiirane 5c. Oil, yield
1
91%. H NMR (CDCl3) d ppm: 2.29 (s; 3H (CH3)); 2.32–
2.61 (dd; 2H (CHCH2S)); 3.26 (m; 1H (CHaHbCHCH2));
3.86 (dd; 1H (OCHaHbCH); JHaHb = 10 Hz); 4.19 (dd;
1H (OCHaHbCH)); 6.80–7.10 (m; 4H (Ph)). 13C NMR
4.6.8. 1-Thiocyanato-3-(p-tolylsulphanyl)propan-2-one 7c.
1
Colourless crystals; mp 40.5–41.5 ꢁC. H NMR (CDCl3):
d ppm: 2.33 (s, 3H (CH3)); 3.72 (s, 2H (CH2SPh)); 4.17
(CDCl3) d ppm: 20.46; 24.02; 31.45; 72.76; 114.57;
25
(s, 2H (CH2SCN)); 7.13–7.27 (m, 4H (Ph)). 13C NMR
129.95; 130.51; 156.27. ½aꢁD ¼ þ11:4 (c 3.16, CHCl3)

1208
E. Łukowska, J. Plenkiewicz / Tetrahedron: Asymmetry 18 (2007) 1202–1209
1
ee = 96%. H NMR and 13C NMR spectra are identical
4.8. General procedure of reduction of ketones 3a–c by
M. isabellina. Preparation of (S)-(2-aryloxymethyl)thiiranes
with those given in the lit.18
Wet mycelium (94 g) was suspended in 240 mL of 2% glu-
cose solution and 1.93 mmol of the appropriate substrate
3a–c dissolved in minimum volume of DMF was added.
The mixture was shaken at 30 ꢁC and 140 rpm and the con-
version was monitored by gas chromatography. After the
appropriate time, ethyl acetate (100 mL) was added to
the flask, and stirring was continued for 30 min. The bio-
mass was filtered off and the supernatant was extracted
with ethyl acetate. The organic layer was dried over anhy-
drous MgSO4 and the solvent evaporated under reduced
pressure. To the crude mixture, 28 mL of THF and a solu-
tion of LiOH (4 mmol) in 5 mL of H2O were added. The
mixture was stirred at room temperature and the progress
of the reaction was monitored by TLC using n-hexane:ethyl
acetate (3:1 v/v) as the eluent. After completion of the reac-
tion (about 2 h) the organic layer was separated and the
solvent was evaporated. The crude mixture was purified
by chromatography on a short silica-gel column with n-
hexane:ethyl acetate (7:1 v/v) as the eluent. The yields
and enantiomeric excesses of the prepared (S)-(2-aryloxy-
methyl)thiiranes are summarized in Table 8.
4.7.4. (R)-(+)-2-((2-Chlorophenoxy)methyl)thiirane 5d. Oil,
yield 86.5%. H NMR (CDCl3) d ppm: 2.35–2.63 (m; 2H
(CHCH2S)); 3.32 (m; 1H (OCH2CHCH2)); 3.93 (dd; 1H
(OCHaHbCH); JHaCH = 7.2 Hz; JHaHb = 10.4 Hz); 4.31
(dd; 1H (OCHaHbCH); JHbCH = 5.2 Hz); 6.91–7.39
(m; 4H (Ph)). 13C NMR (CDCl3) d ppm: 24.02; 31.02;
1
73.83; 114.43; 122.14; 123.34; 127.70; 130.41; 153.94.
25
½aꢁD ¼ þ3 (c 2, CHCl3) ee = 99%. Anal. Calcd for
C9H9SOCl: C, 53.86; H, 4.52; S, 15.98; Cl, 17.67. Found:
C, 53.76; H, 4.40; S, 16.09; Cl, 17.72.
4.7.5. (R)-(+)-2-(o-Tolyloxymethyl)thiirane 5e. Oil, yield
1
79%. H NMR (CDCl3) d ppm: 2.28 (s; 3H (CH3)); 2.34–
2.63 (m; 2H (CHCH2S)); 3.31 (m; 1H (OCH2CHCH2));
3.95 (dd; 1H (OCHaHbCH); JHaCH = 6.8 Hz; JHaHb
=
10.4 Hz); 4.22 (dd; 1H (OCHaHbCH); JHbCH = 5.6 Hz);
6.81–7.18 (m; 4H (Ph)). 13C NMR (CDCl3) d ppm:
16.18; 23.82; 31.59; 72.63; 111.52; 120.90; 126.74; 127.04;
31:5
130.78; 156.52. ½aꢁD ¼ þ13:6 (c 2.5, CHCl3) ee =
92%. Anal. Calcd for C10H12OS: C, 66.63; H, 6.71; S,
17.79. Found: C, 66.54; H, 6.65; S, 17.34.
20:5
4.8.1. (S)-(ꢀ)-2-(Phenoxymethyl)thiirane 5a. ½aꢁD
¼
ꢀ4:86 (c 1.64) ee = 27%.
4.7.6. (R)-(ꢀ)-2-(Phenylsulphanylmethyl)thiirane 9a. Oil,
yield 73%. 1H NMR (CDCl3) d ppm: 2.10 (dd; 1H
(CHCHaHbS); JHaCH = 1.6 Hz; JHaHb = 5.2 Hz); 2.48 (dd;
1H (CHCHaHbS); JHbCH = 2.4 Hz); 2.79 (dd; 1H
(PhSCHcHdCH); JHcCH = 8.8 Hz; JHcHd = 13.6 Hz); 3.11
24
4.8.2. (S)-2-((4-Chlorophenoxy)methyl)thiirane 5b. ½aꢁD ¼ 0
(c 0.92) ee = 13%.
25
4.8.3. (S)-(ꢀ)-2-(p-Tolyloxymethyl)thiirane 5c. ½aꢁD
¼
ꢀ3:4 (c 2.36) ee = 30%.
(m; 1H (CH)); 3.45 (dd; 1H (PhSCHcHdCH); JHdCH
=
5.2 Hz); 7.23–7.46 (m; 5H (Ph)). 13C NMR (CDCl3) d
ppm: 26.01; 33.55; 41.16; 127.06; 129.07; 131.06; 135.04.
29
1
½aꢁD ¼ ꢀ32:8 (c 5, CHCl3) ee = 55%. H NMR and 13C
Acknowledgements
NMR spectra are identical with those given in the lit.18
We acknowledge the evaluation of this manuscript by
Professor Jerzy Lange and many valuable suggestions
provided by him. The work was financially supported by
Warsaw University of Technology.
4.7.7. (R)-(ꢀ)-2-((4-Chlorophenylsulphanyl)methyl)thiirane
9b. Oil, yield 62.5%. 1H NMR (CDCl3) d ppm: 2.10
(dd; 1H (CHCHaHbS); JHaCH = 1.6 Hz; JHaHb = 5.6 Hz);
2.48 (dd; 1H (CHCHaHbS); JHbCH = 2.4 Hz); 2.81 (dd;
1H (PhSCHcHdCH); JHcCH = 8.4 Hz; JHcHd = 13.6 Hz);
References
3.08 (m; 1H (CH)); 3.39 (dd; 1H (PhSCHcHdCH); JHdCH
=
4.8 Hz); 7.26–7.38 (m; 4H (Ph)). 13C NMR (CDCl3) d ppm:
´
´
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25
1
½aꢁD ¼ ꢀ44:95 (c 5, CHCl3) ee = 80%. H NMR and 13C
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