On the stereochemistry of the Baker's Yeast-mediated reduction of regioisomeric unsaturated aldehydes: Examples of enantioselectivity switch promoted by substrate-engineering

Article abstract of DOI:10.1016/j.molcatb.2012.02.003

The Baker's Yeast (BY) reduction of (Z)-2-chloromethyl-3-arylacrylaldehydes was found to afford (R)-2-methyl-3-aryl-propanols showing high enantiomeric excess values. Deuterium incorporation experiments were performed, in order to investigate the mechanism of the bioreduction: the formation of the corresponding substituted 2-benzylacrylaldehydes, as intermediates to be effectively reduced by Baker's Yeast, was suggested. These intermediates were synthesized and submitted to BY reduction to afford the corresponding saturated (R)-alcohols, thus confirming the conclusions drawn from labelling experiments. The enantioselectivity of their bioreduction was found to be opposite with respect to that observed for the corresponding regioisomeric 2-methylcinnamaldehydes. The preparation of the two enantiomers of 2-methyl-3-aryl-propanols by fermentation of two regioisomers represents an interesting example of substrate-controlled enantioselective reaction.

Full text of DOI:10.1016/j.molcatb.2012.02.003

Journal of Molecular Catalysis B: Enzymatic 84 (2012) 94–101
Contents lists available at SciVerse ScienceDirect
Journal of Molecular Catalysis B: Enzymatic
journal homepage: www.elsevier.com/locate/molcatb
On the stereochemistry of the Baker’s Yeast-mediated reduction of regioisomeric
unsaturated aldehydes: Examples of enantioselectivity switch promoted by
substrate-engineering
Elisabetta Brennaa,∗, Giovanni Fronzab,1, Claudio Fugantia, Francesco G. Gattia, Alessia Manfredia,
Fabio Parmeggiania, Paolo Ronchia
a Politecnico di Milano, Dipartimento di Chimica, Materiali ed Ingegneria Chimica, Via Mancinelli 7, I-20131 Milano, Italy
b Istituto di Chimica del Riconoscimento Molecolare – CNR, Dipartimento di Chimica, Materiali ed Ingegneria Chimica, Via Mancinelli 7, I-20131 Milano, Italy
a r t i c l e i n f o
a b s t r a c t
Article history:
Available online 9 March 2012
The Baker’s Yeast (BY) reduction of (Z)-2-chloromethyl-3-arylacrylaldehydes was found to afford
(R)-2-methyl-3-aryl-propanols showing high enantiomeric excess values. Deuterium incorporation
experiments were performed, in order to investigate the mechanism of the bioreduction: the forma-
tion of the corresponding substituted 2-benzylacrylaldehydes, as intermediates to be effectively reduced
by Baker’s Yeast, was suggested. These intermediates were synthesized and submitted to BY reduction to
afford the corresponding saturated (R)-alcohols, thus confirming the conclusions drawn from labelling
experiments. The enantioselectivity of their bioreduction was found to be opposite with respect to that
observed for the corresponding regioisomeric 2-methylcinnamaldehydes. The preparation of the two
enantiomers of 2-methyl-3-aryl-propanols by fermentation of two regioisomers represents an interesting
example of substrate-controlled enantioselective reaction.
Keywords:
Baker’s Yeast
Enantioselectivity
Reduction
Unsaturated aldehydes
Deuterium NMR spectroscopy
© 2012 Elsevier B.V. All rights reserved.
1. Introduction
ene-reductases [11] into (S)- and (R)-2,4,4-trichlorobutanoic acids,
respectively. In 2007 Faber et al. reported the bioreduction of the
Since the early seventies the growing interest for small chiral
molecules, to be used as building blocks for the synthesis of more
complex enantiopure compounds, [1] has promoted the study of
microbial transformations of non conventional substrates [2–4].
However, the major drawback of this approach is that biocatalysed
reactions usually afford only one enantiomer of the final molecule
with high enantioselectivity. If the other enantiomer is needed,
efforts have to be devoted to obtain it by acting on the choice of
the biocatalyst or on the structure of the starting substrate. In the
case of secondary alcohols, derived from the reduction of a prochi-
ral ketone, useful results were obtained by growing cultures from
different strains of the same microorganism [5], or using different
microorganisms on the same substrate [6–8] or the same microor-
ganism on modified substrates [9].
dimethyl esters of citraconic and mesaconic acid into the (R)- and
(S)-enantiomers of methyl 2-methylsuccinate by means of isolated
enzymes [12].
Recently, we have been interested in the BY fermentation
of chloro aldehydes. We found that aldehyde (E)-1 (Scheme 1)
was converted by Baker’s Yeast into saturated alcohol (S)-2
with an enantiomeric excess (ee) value of 70% [13]. Deuterium
incorporation experiments showed that the conversion of com-
pound 1 into derivative 2 proceeded through intermediate 3,
which gave upon dehydroalogenation in the fermentation medium
␣-methylcinnamaldehyde ((E)-4), the real substrate for the BY
Among chiral compounds prepared by enzyme-mediated reduc-
tion of the double bond of activated olefins, a remarkable example
is that of (Z)- and (E)-methyl 2,4,4-trichloro-2-butenoates, trans-
formed by fermenting Baker’s Yeast (BY) [10], and by isolated
∗
Corresponding author. Tel.: +39 02 23993077; fax: +39 02 23993180.
E-mail addresses: elisabetta.brenna@polimi.it (E. Brenna),
giovanni.fronza@polimi.it (G. Fronza).
1
Tel: +39 02 23993027; fax: +39 02 23993180.
Scheme 1. BY reduction of chloro aldehyde (E)-1.
1381-1177/$ – see front matter © 2012 Elsevier B.V. All rights reserved.
doi:10.1016/j.molcatb.2012.02.003

E. Brenna et al. / Journal of Molecular Catalysis B: Enzymatic 84 (2012) 94–101
95
OMe
Me
2
3
Ar
1 OH
Scheme 2. BY reduction of chloro aldehyde (Z)-6.
16
2H-1
H-3 H-3
H-2
a
Scheme 3. Substrates for bioreductions.
H
D
H
D H
D
D H
+
2
2
Ar
3
3
1
Ar
OH
1
OH
production of (S)-2 [14]. Yeast fermentation of 1 afforded also diol
5 by reduction of the hydroxy ketone, which was generated in the
acyloin-type condensation promoted by BY on unsaturated alde-
hyde 1 [15].
We now report on the conversion of chloromethyl cinnamalde-
hyde (Z)-6 (Scheme 2), a regioisomer of compound 1, into saturated
alcohol (R)-2 by BY fermentation, likely through the formation
of intermediate benzylacrylaldehyde 7, which is a regioisomer of
compound 4. Aldehyde 7 can be generated by dehydrohalogenation
of saturated chloro aldehyde 8 in the reaction medium.
D
CH3
H3C
D
(1R,2S,3S)- 21 (77%)
(1R,2R,3S)- 21 (23%)
D-1
D-2
D-3
b
The same behaviour under BY fermentation is herein described
also for chloro aldehydes (Z)-9 and (Z)-10 (Scheme 3), and the
results of labelling experiments are presented to confirm that sub-
stituted benzylacrylaldehydes 7, 11 and 12 are the intermediates
effectively reduced by BY. The hypothesis, that the different enan-
tioselectivity observed in the reduction of (E)-1 and (Z)-6 is due
to the formation of two regioisomeric unsaturated aldehydes, has
induced us to further investigate the role played on the stereochem-
H
D
H
D
H
D
H
D
+
2
2
3
1
3
Ar
Ar
1
OH
OH
CH2D
DH2C
D
D
(1R,2R,3S)- 20 (87%) (1R,2S,3S)- 20 (13%)
D-2
CH2D
ical course of the reaction by the position of the conjugated C
C
D-1
double bond with respect to the aldehydic moiety. Thus, aldehydes
7, 11 and 12 have been synthesised on purpose, and submitted to
BY fermentation. The results of their reduction are herein compared
with the data regarding the BY-mediated reduction of the corre-
sponding cinnamaldehydes (E)-4, (E)-13, and (E)-14 (Scheme 3).
D-3
c
2. Results and discussion
3.5
3.0
2.5
2.0
1.5
1.0
ppm
Fig. 1. (a) Proton spectrum (CDCl3) of racemic 16; (b) deuterium spectrum (CHCl3)
of (1R,2S,3S)-21 (main product) obtained by BY reduction of (E)-4 in H2O/D2O 1%;
(c) deuterium spectrum (CHCl3) of (1R,2R,3S)-20 (main product) obtained by BY
reduction of (Z)-10 in H2O/D2O 1% (Ar = 3-methoxyphenyl).
2.1. Baker’s Yeast reduction of chloro aldehydes (Z)-6, (Z)-9, and
(Z)-10 and deuterium incorporation experiments.
In the biocatalysed reduction of chloro aldehydes (Z)-6, (Z)-
9, and (Z)-10 different results were observed according to the
mode employed for adding the substrate to fermenting BY. When
the chloro aldehydes were adsorbed on a hydrophobic resin
(polystyrene XAD-1180N, 1:15 w/w), and then suspended in the
aqueous medium, only the (R)-enantiomers of the corresponding
saturated alcohols 2, 15 and 16 (Scheme 4) were obtained in high
enantiomeric excess (Table 1). These feeding conditions are known
to ensure very low substrate concentration in the fermentation
medium [16].
Conversely, when the aldehydes were added as an ethanolic
solution, racemic diols 17–19 (Scheme 4) were obtained in ca. 1:2
mixture with the corresponding saturated (R)-alcohol showing low
ee.
To support the mechanism outlined in Scheme 2 for the conver-
sion of unsaturated chloromethyl aldehydes (Z)-6, (Z)-9, and (Z)-10
into saturated (R)-alcohols 2, 15, and 16, deuterium incorporation
experiments were performed. Aldehyde (Z)-10 was treated with
fermenting Baker’s Yeast in the presence of D2O, and the resulting
deuterated reduction product 20 was submitted to 2H NMR stud-
ies (Fig. 1). This compound was chosen for the interpretation of 2
H
NMR spectra, because it showed the natural abundance signal of
the O-methyl group at 3.81 ppm intense enough to allow a proper
evaluation of the contribution of deuterium natural abundance to
the intensity of the signals of the deuterium atoms incorporated
during the bioreduction.
Scheme 4. Products of BY reduction of chloroaldehydes (Z)-6, 9, and 10.

96
E. Brenna et al. / Journal of Molecular Catalysis B: Enzymatic 84 (2012) 94–101
Table 1
Conversion (c) and enantiomeric excess (ee) values for the bioreduction of aldehydes (Z)-6, (Z)-9, (Z)-10, 7, 11, 12, (E)-4, (E)-14, (E)-15 to afford the corresponding alcohols
2, 15, and 16.
CHO
Ar
CHO
CHO
Ar
Ar
Cl
ca [%]
49
eea [%]
ca [%]
60
eea [%]
c [%]
12b
13
ee [%]
70b
(S)
(Z)-6
Ar = Ph
(Z)-9
Ar = 4-ClC6H4
(Z)-10
Ar = 3-MeOC6H4
99
(R)
96
(R)
98
(R)
7
95
(R)
69
(R)
94
(R)
(E)-4
Ar = Ph
(E)-14
Ar = Ph
11
78c
(S)
29
33
Ar = 4-ClC6H4
12
Ar = 3-MeOC6H4
Ar = 4-ClC6H4
(E)-15
Ar = 3-MeOC6H4
54d
21
28
44d
(S)
a
Conversion (c) and enantiomeric excess values (ee) are referred to the reaction performed with the substrate adsorbed on resins, and they are calculated by GC analysis
(on a chiral stationary phase) of the crude mixture after 48 h reaction time; conversion is expressed as percentage of the saturated alcohol in the reaction mixture.
b
Isolated yields and ee value from Ref. [13].
Conversion values determined by GC analysis and ee value from Ref. [26].
Conversion (c) and enantiomeric excess values (ee) are referred to the reaction performed with the substrate dissolved in ethanol, conversion is calculated by GC/MS
c
d
analysis of the crude mixture after 48 h reaction time; ee value is determined by HPLC analysis (on a chiral stationary phase).
The 2H NMR spectrum of 20 (Fig. 1c) was compared with that
of the deuterated saturated alcohol 21 (Fig. 1b) obtained by BY fer-
mentation of the corresponding cinnamaldehyde (E)-14 [17]. The
signal assignment was performed by considering the 1H NMR spec-
trum of the synthetic saturated alcohol 16 (Fig. 1a).
the main component by comparison with the deuterium spectrum
of (1R,2S,3S)-21.
The first observation is that the two compounds have oppo-
site configuration at C2, because the experimental evidence is that
BY-mediated reduction afforded saturated alcohols (S)- and (R)-
16 from (E)-14 and (Z)-10, respectively. Fig. 1b and c clearly show
that the chemical shifts of D-1 and D-3 in alcohol 20 are differ-
ent from those of the corresponding deuterium atoms in derivative
21, where they are both characterised by anti arrangement with
respect to D-2. Thus, a syn,syn relative configuration can be estab-
lished for D-1, D-2, and D-3 in compound 20. The configuration of
The spectrum of 21 (Fig. 1b) is characterised by three intense
signals at 1.96 ppm (2S-D), 2.42 ppm (3S-D) and 3.49 ppm (1R-D),
while that of compound 20 (Fig. 1c) shows four intense deuterium
peaks at 0.94 ppm (methyl group at position 2), 1.96 ppm (2R-D),
2.74 ppm (3S-D) and 3.54 ppm (1R-D). Each spectrum shows also
less intense signals belonging to the diastereotopic nuclei at posi-
tions 1 and 3, because the 2H NMR spectra were recorded on the
compounds recovered from fermentation reactions performed in
the absence of resins. These materials were obtained in higher
yields, but lower stereoisomeric purity (enantiomeric purity when
the reaction was performed in water; diastereoisomeric purity
when the reaction was carried out in the presence of D2O, with
de = 54% for 21 and 74% for 20). The peaks at 3.81 ppm in Fig. 1b and
c, and that at 0.94 ppm in Fig. 1b are due to the natural abundance
deuterium nuclei of the methoxy and methyl groups, respectively.
The absolute configuration of compounds 20 and 21 was
assigned on the basis of these considerations. In a previous work
[13], the BY-mediated reduction of (E)-4 to saturated alcohol (S)-
2 was established to occur according to an anti mechanism, with
the substrate in a flipped binding mode, in order to account for
the (S) configuration of the resulting compound [18]. The anti addi-
tion was established by comparison of the 2H NMR spectrum of
the deuterated product recovered from BY fermentation with those
of stereospecifically deuterated synthetic species. Thus, as for cin-
namaldehyde (E)-14, the addition to C␤-re face of a D− from the
cofactor (which has exchanged the hydrogen to be delivered in the
reduction with deuterated water [19]) and of a D+ to C␣-re face
from the solvent gave the deuterated saturated aldehyde shown in
Scheme 5a, which was then reduced by one of the alcohol dehy-
drogenases active in fermenting BY to afford compound 21. The
absolute configuration of the stereogenic centres C2 and C3 in com-
pound 21 was thus assigned to be (2S,3S), while that of C1 was
established to be R on the basis of the known mode of BY reduc-
tion of the carbonyl group of cinnamaldehyde [20,21]. The sample
contained also 23% of the diastereoisomer (1R,2R,3S)-21, due to the
lower stereoselectivity of the bioreduction when the substrate was
added in ethanol solution.
C1 is in agreement with the known mode of BY-mediated reduction
of the carbonyl group of cinnamaldehyde.
The second important consideration is that compound 20
is characterised by the incorporation of four deuterium atoms,
whereas only three of them are inserted in the structure of deriva-
tive 21. In particular, the labelling of the methyl group in position 2
of compound 20, together with the presence of a deuterium atom
at C2, supports the formation of methoxybenzyl acrylaldehyde 12
as intermediate in the generation of the corresponding saturated
alcohol from (Z)-10.
Scheme 5b shows the steps of deuterium incorporation in the
BY reduction of (Z)-10 to (1R,2R,3S)-20, which are in agreement
with the absolute configuration obtained by the analysis of the
deuterium spectrum. In the first step deuterium addition occurs
to the C C double bond of chloro aldehyde (Z)-10 with anti stere-
ochemistry: D− is delivered to C␤-re face, and D+ to C␣-si face. This
latter deuterium atom in indeed lost in the dehydrohalogenation
step, to afford deuterated 12. The configuration of C3 requires a
flipped binding mode of the starting substrate in the enzyme active
site [18]. The same anti stereochemistry of double bond reduction
occurs in the following step: the addition of a D− from the cofactor
to C␤, and a of D+ from the solvent to C␣-si face of deuterated 12
finally gives (1R,2R,3S)-20, as the main product.
As mentioned earlier, alcohols 2, 15, and 16 were the only
transformation products when aldehydes (Z)-6, 9 and 10 were
administered to fermenting BY loaded on adsorption resins, with no
trace of those vic-diols produced by reduction of the acyloin inter-
mediates, usually obtained from a variety of ␣,␤-unsaturated and
aromatic aldehydes [22]. However, when aldehydes (Z)-6, 9 and 10
were administered to Baker’s Yeast in ethanolic solution, they pro-
vided 1,3-diols, shown to possess structural formulas 17, 18 and 19
by spectroscopic studies and comparison with reported data [23],
in ca. 1:2 ratio with the saturated (R)-alcohols 2, 15, and 16. These
diols showed small negative optical rotation values. In particular,
The 2H NMR spectrum of compound 20 (Fig. 1c) showed the
presence of four deuterium atoms in position 1, 2, 2ꢀ and 3, and
absolute configuration (1R,2R,3S) was tentatively established for

E. Brenna et al. / Journal of Molecular Catalysis B: Enzymatic 84 (2012) 94–101
97
Scheme 5. Deuterium incorporation in the BY reduction products of (a) (E)-14 and of (b) (Z)-10 in D2O (ER = ene-reductase; ADH = alcohol dehydrogenase; Ar = 3-
methoxyphenyl).
diol 17 displayed [␣]D = −1.6 (c 1, CHCl3), and no baseline-resolved
peaks could be obtained for these products by either HPLC or GC
analysis on a chiral stationary phase.
aldehyde 27 is reduced to provide diol 19. At the moment, the rea-
sons for the low or nil enantiomeric enrichment of 17, 18 and 19,
as compared with 24 and 25, are obscure.
The formation of structurally related 1,3-diols from ␣,␤-
unsaturated aldehydes in fermenting Baker’s Yeast is not new. The
benzoyl and the benzyl derivatives of 4-hydroxy crotonaldehyde
22 and 23 (Scheme 6), respectively, provided diols (R)-24 and 25
showing good enantiomeric purity [24]. The BY generation of these
diols was explained from the mechanistic point of view by a stere-
ospecific reversible water addition ␤ to the carbonyl group of 22
and 23, mediated by a lyase, followed by reduction of the interme-
diate ␤-hydroxy aldehyde by yeast alcohol dehydrogenase. When
regiospecifically deuterated 22 was incubated with BY, partial loss
and scrambling of the label in the position of derivative 24 corre-
sponding to position 2 of the precursor 22 was observed.
The generation of 17, 18 and 19 from (Z)-6, 9 and 10 follows a
pathway similar to the one suggested for 24 and 25 from 22 and
23, as it is outlined in Scheme 7 for the conversion of (Z)-10 into
diol 19. An initial Michael-type addition of water in position 3 of
the unsaturated aldehyde 10 provides (step a) ␤-hydroxy aldehyde
26. The hydrogen atom in position 2 of this kind of intermediates
should be very labile, as one can judge from the extended loss of
deuterium in the suggested intermediate for the conversion of 22
into 24. Accordingly, dehydrohalogenation of 26 (step b) affords
unsaturated aldehyde 27. Finally, in step c the carbonyl group of
Evidence supporting this mechanistic proposal arose from 2H
NMR studies of the product obtained by biotransformation of (Z)-
10 in deuterated water. Fig. 2a shows the proton NMR spectrum
of 19, obtained from (Z)-10 in tap water, with the corresponding
signal assignment, while Fig. 2b is the 2H NMR spectrum of 28,
deuterated analogue of 19, produced from (Z)-10 in the presence of
deuterated water. The incorporation of one deuterium in position 1
of 28 (Fig. 2b) (signals at 4.01 and 3.85 ppm) thus demonstrates that
step c of Scheme 7 is biocatalysed, with addition of a D− to C1 from
the reduced cofactor. The stereospecificity of yeast alcohol dehy-
drogenase carbonyl reduction (which should have provided (R)-28
is well established. Thus, the nearly 1:1 ratio of the deuterium sig-
nals of Fig. 2b should lead to the conclusion that water addition to
the double bond of 10 is not stereospecific. However, steps a and c
of Scheme 7 must be under enzymatic control, since aldehyde 10
was recovered unaltered from 7 days incubation in water/ethanol
in the presence of d-glucose, at the same temperature and dilution
used in the yeast transformation.
2.2. Baker’s Yeast reduction of substituted benzylacrylaldehydes
7, 11, and 12
Substituted benzylacrylaldehydes 7, 11, and 12 were synthe-
sised and their bioreduction was investigated, in order to further
support the hypothesis of their formation as intermediates in the
BY mediated conversion of chloromethyl arylacrylaldehydes into
saturated alcohols.
The BY reduction of benzylacrylaldehyde 7 had been already
described in the literature [25] to afford modest yields (20%) of
nearly enantiomerically pure (R)-2 (ee = 98%) through a slow addi-
tion (96 h) of an ethanolic solution of the substrate to the reaction
medium.
Scheme 6. Products obtained by BY reduction of 4-oxygen substituted crotonalde-
hyde.

98
E. Brenna et al. / Journal of Molecular Catalysis B: Enzymatic 84 (2012) 94–101
Scheme 7. Steps in the conversion of (Z)-10 into 19.
Substrates 7, 11, and 12 were adsorbed on a hydrophobic
considerations to be made on the possibility to drive the enantios-
electivity of BY carbon carbon double bond reduction by a careful
choice of the structure of the starting substrates. The two sets of
regioisomeric aldehydes are bound in the active site of the enzyme
according to the same mode, as it is drawn in Scheme 5a and b for
3-methoxy derivatives (E)-14 and 12. However, the position of the
double bond is such that the addition of the proton from the solvent
occurs on C␣-re face and C␣-si face, respectively.
resin (polystyrene XAD-1180 N, 1:15 w/w), and suspended in fer-
menting BY. After 48 h, saturated (R)-alcohols 2, 15, and 16 were
recovered: the conversion and ee values are reported in Table 1. As
for compound 7, complete consumption of the starting aldehyde
was observed, with formation of a 6:4 mixture of (R)-2 (ee = 95%)
and of the corresponding allylic alcohol. 45% of aldehyde 11 was still
present after 48 h, together with 33% of alcohol (R)-15 (ee = 69%)
and 22% of the allylic alcohol. When aldehyde 12 was the sub-
strate, (R)-16 (ee = 98%) was obtained in 28%, together with 33%
of the unreacted starting aldehyde and 39% of the allylic alcohol.
The stereochemistry of the reduction was the same observed in the
conversion of chloromethyl cinnamaldehydes, and opposite to that
found in the BY reduction of (E)-cinnamaldehydes 4, 13 [26] and 14
(Table 1).
The absolute configuration of (R)-(+)-2 was known [13], and that
of the saturated alcohols 15 and 16 was tentatively assigned by
considering the accepted stereochemistry for the reduction of ␣-
methylcinnamaldehydes(Ref. [26]for (S)-(−)-15obtainedfrom(E)-
13, this work for (S)-(−) and (R)-(+)-16, respectively obtained from
(E)-14 and 11)
3. Conclusion
The investigation of the mechanism of BY reduction of
chloromethyl aldehydes (Z)-6, 9, and 10 by deuterium incorpora-
tion experiments, and the comparison with the behaviour of chloro
aldehyde (E)-1 under the same reaction conditions allowed us to
make some considerations on the stereochemistry of carbon carbon
double bond bioreduction. In particular, we could put into evidence
the importance of the position of the double bond to be reduced
with respect to the activating aldehydic group. The hypothesis that
the different enantioselectivity was due to the formation of two
regioisomeric intermediates, i.e. 4 and 7, was further supported by
the analysis of the stereochemical outcome of two sets of regioiso-
meric aldehydes, i.e. 7, 11, 12 and 4, 13, 14.
The stereochemical outcome of the two sets of regioiso-
meric aldehydes, i.e. 7, 11, 12 and 4, 13, 14, allowed for some
The results of this research demonstrate also the utility of fer-
menting Baker’s Yeast in the discovery of new multienzymatic
transformations of non-conventional substrates, leading to syn-
thetically useful unexpected products. For example, saturated
alcohol (R)-16 is now available by BY reduction, and it can be used
as starting material for the synthesis of the pain-relief therapeutic
agent (1R,2R)-tapentadol (Nucynta) [27].
4. Experimental
TLC analyses were performed on Merck Kieselgel 60 F254
plates. All the chromatographic separations were carried out on
silica gel columns. 1H and 13C NMR spectra were recorded on
a 400 MHz spectrometer. The chemical shift scale was based
on internal tetramethylsilane. GC–MS analyses were per-
formed using
a
HP-5MS column (30 m × 0.25 mm × 0.25 ␮m).
The following temperature program was employed: 60◦
(1 min)/6◦/min/150◦ (1 min)/12◦/min/280◦ (5 min). The enan-
tiomeric excess values of the samples of saturated alcohol 2
and 15 were determined by GC analysis performed using a
DAcTBSil.BetaCDX 0.25 ␮m × 0.25 mm × 25 m column (Mega,
Italy), according to the following conditions: (i) compound
2: 80 ◦C (2 min)/1 ◦C min−1/120 ◦C/30 ◦C min−1/220 ◦C: (R)-
2
tR = 16.1 min, (S)-2 tR = 16.5 min; (ii) compound 15: 90 ◦C
(2 min)/1 ◦C min−1/140 ◦C/30 ◦C min−1/220 ◦C: (R)-15 tR = 40.6 min,
(S)-15 tR = 41.0 min. The enantiomeric excess values of the sam-
ples of saturated alcohol 16 were determined by HPLC analysis
using a Chiralcel OD column, according to the following condi-
tions: hexane: isopropanol 9:1, flow 0.6 ml/min, ꢀ = 210 nm; tR
(S)-16 = 13.42 min, tR (R)-17 = 16.17 min.
4.1. Acquisition of the 2H spectra
Fig. 2. (a) Proton spectrum (C6D6) of 19 and (b) deuterium spectrum (C6H6) of
28 obtained by BY reduction of (Z)-10 in H2O/D2O 1%. The signals at 3.36 and
5.06–5.17 ppm are due to the natural abundance deuterium present, respectively,
at the OCH3, H-2ꢀ and H-3 positions.
The 2H spectra were measured on a Bruker Avance 500 spec-
trometer equipped with a 10-mm probe head and 19F lock channel

E. Brenna et al. / Journal of Molecular Catalysis B: Enzymatic 84 (2012) 94–101
99
under CPD (Waltz 16 sequence) proton decoupling conditions at
the temperature of 305 K. The solutions were prepared dissolv-
ing 20–100 mg of material in ca. 3.0 mL of CHCl3 or C6H6 adding
about 40 ␮L of C6F6 for the lock. The spectra were run collect-
ing 1024–4096 scans depending on the solution concentration
using the following acquisition parameters: 5.4 s acquisition time,
1530 Hz spectral with, 16 K time domain and 1 s delay. The spectra
were Fourier transformed with a line broadening of 0.3 Hz, manu-
ally phased and integrated after an accurate correction of the base
line. For partially overlapped signals the peak areas were deter-
mined through the deconvolution routine of the Bruker TopSpin
NMR software using a Lorentzian line shape.
(Z)-Methyl 2-chloromethyl-3-(4-chlorophenyl)acrylate. Yield
54%; spectroscopic data for this compound are inagreement with
those reported in literature [28].
(Z)-Methyl 2-chloromethyl-3-(3-methoxyphenyl)acrylate. Yield
50%; ıH (400 MHz; CDCl3) 7.85 (1H, s, CH ), 7.35 (1H, m, aromatic
hydrogen), 7.12–7.10 (2H, m, aromatic hydrogens), 6.96–6.94 (1H,
m, aromatic hydrogen), 4.48 (2H, s, CH2Cl), 3.88 (3H, s, OMe), 3.84
(3H, s, COOMe); ıC (100.91 MHz; CDCl3; Me4Si) 39.1, 52.4, 55.2,
114.2, 115.8, 121.9, 128.5, 129.8, 135.3, 143.7, 159.7, 166.6; GC/MS
tR 22.68 min, m/z 242 (M+ +2, 50), 240 (M+, 50), 208 (40), 180 (40),
145(100), 131 (15), 115 (30).
4.2.3. General procedure for the conversion of
2-chloromethyl-3-arylacrylates in the corresponding
2-chloromethyl-3-arylpropenols
4.2. Synthesis of chloromethyl aldehydes (Z)-6, (Z)-9, and (Z)-10
The ester prepared above (50 mmol) in toluene (150 mL) under
stirring at −10 ◦C in a N2 atmosphere was treated dropwise with
a 25% DIBAH solution in toluene (120 mmol). After 16 h acetone
(10 mL) was added dropwise, followed by a sat. solution of potas-
sium sodium tartrate (1.5 vol). After stirring overnight the organic
phase was separated and the aqueous layer was extracted with
toluene. The combined organic phase was washed with water, dil.
cold HCl and brine. The oily residue obtained upon evaporation of
the dried organic phase and chromatographed on a silica gel column
with increasing amounts of ethyl acetate in hexane.
(Z)-2-Chloromethyl-3-phenylprop-2-en-1-ol. Yield 90%; ıH
(400 MHz; CDCl3) 7.40–7.25 (5H, m, aromatic hydrogens), 6.76
(1H, s, CH C), 4.39 (2H, m, CH2OH or CH2Cl), 4.29 (2H, s, CH2Cl or
CH2OH); ıC (100.91 MHz; CDCl3) 40.8, 64.9, 127.7, 128.5, 128.6,
130.9, 135.7, 136.1; GC–MS tR = 19.20 min m/z 184 (M+ +2, 35), 182
(M+, 50), 147 (20), 133 (70), 115 (100), 91 (80).
These substrates were prepared according to this sequence: the
Baylis–Hillman adducts, obtained by reaction of the corresponding
aromatic aldehyde and methyl acrylate in the presence of DABCO
(1,4-diazabicyclo[2.2.2]octane), were treated with CCl4/PPh3 to
afford the corresponding chloromethyl esters. These derivatives
were submitted to DIBAH (diisobutylaluminium hydride) reduc-
tion to afford the allylic alcohols, which gave upon MnO2 oxidation
the desired chloromethyl aldehydes.
4.2.1. General procedure for the preparation of the
Baylis–Hillman adducts [28]
Neat aldehyde (100.0 mmol) was added to a stirred solu-
tion of methyl acrylate (12.91 g, 150 mmol) and DABCO (11.15 g,
100 mmol) and left to stir overnight at room temperature. After
24–48 h the reaction was complete. The reaction mixture was
diluted with diethyl ether (500 mL) and washed twice with 2 N HCl
(100 mL), 2 N NaOH (50 mL) and brine (2 × 50 mL). The organic layer
was separated and dried (Na2SO4). The oily residue obtained upon
evaporation of the solvent was chromatographed on a silica gel
column with increasing amounts of ethyl acetate in hexane.
Methyl 2-(hydroxy(phenyl)methyl)acrylate. Yield 80%; spectro-
scopic data for this compound are in agreement with those reported
in literature [29].
(Z)-2-Chloromethyl-3-(4-chlorophenyl)prop-2-en-1-ol.
Yield
70%; ıH (400 MHz; CDCl3;) 7.25 (2H, m, aromatic hydrogens), 7.19
(2H, m, m, aromatic hydrogens), 6.60 (1H, s, CH ), 4.28 (2H, s,
CH2OH or CH2Cl), 4.14 (2H, s, CH2OH or CH2Cl); ıC (100.91 MHz;
CDCl3; Me4Si) 40.5, 64.7, 128.8, 129.5, 129.9, 133.6, 134.1, 137.5;
GC–MS tR = 21.85 min m/z 218 (M+ +2, 50), 216 (M+, 50), 181 (25),
167 (80), 151 (70), 115 (100).
(Z)-2-Chloromethyl-3-(3-methoxyphenyl)prop-2-en-1-ol. Yield
80%; ıH (400 MHz; CDCl3) 7.28 (1H, m, m, aromatic hydrogens),
6.94–6.93 (2H, m, m, aromatic hydrogens), 6.86–6.84 (1H, m,
H(Ar)), 6.72 (1H,s, CH ), 4.37 (2H, s, CH2OH or CH2Cl), 4.28 (2H,
s, CH2Cl or CH2OH), 3.81 (3H, s, OMe); ıC (100.91 MHz; CDCl3;
Me4Si) 40.8, 55.2, 64.7, 113.5, 113.8, 121.1, 129.6, 130.8, 129.6,
137.0, 159.6; GC–MS tR = min 22.22 min m/z 214 (M+ +2, 30), 212
(M+, 100), 176 (40), 159 (95), 145 (60), 115 (70), 91 (40).
Methyl 2-((4-chlorophenyl)(hydroxy)methyl)acrylate. Yield 78%;
spectroscopic data for this compound are in agreement with those
reported in literature [30].
Methyl 2-(hydroxy(3-methoxyphenyl)methyl)acrylate. Yield 91%;
ıH (400 MHz; CDCl3) 7.25 (1H, m, aromatic hydrogen), 6.94–6.95
(2H, m, aromatic hydrogens), 6.82 (1H, dd, J 7.8 and 1.4 Hz, aro-
matic hydrogen), 6.33 (1H, m, CHH ), 5.83 (1H, m, CHH ), 5.53 (1H,
s, PhCHOH), 3.79 (3H, s, OMe), 3.72 (3H, s, COOMe); ıC (100.91 MHz;
CDCl3) 51.9, 55.2, 73.0, 112.0, 113.3, 118.8, 126.2, 129.4, 141.7,
142.9, 159.6, 166.7; GC/MS tR 21.29 min, m/z 222 (M+, 60), 190 (50),
162 (50), 135(100), 109 (50).
4.2.4. General procedure for the oxidation of
2-chloromethyl-3-arylpropenols to
2-chloromethyl-3-arylacrylaldehydes
The allylic alcohol (35 mmol) was dissolved in dichloromethane
(50 mL) and treated with 4 parts by weight of activated MnO2 under
stirring overnight at r.t. The reaction mixture was filtered by suction
over a CeliteTM pad. The mass on the filter was washed repeatedly
with dichloromethane. The oily residue obtained upon evaporation
of the solvent was chromatographed on a silica gel column with
increasing amounts of ethyl acetate in hexane.
(Z)-2-(Chloromethyl)-3-phenylacrylaldehyde ((Z)-6) [33] Yield
70%; ıH (400 MHz; CDCl3) 9.56 (s, 1H, CHO), 7.67–7.64 (m, 2H, aro-
matic hydrogens), 7.51–7.47 (m, 3H, aromatic hydrogens), 7.44 (s,
1H, CH ), 4.40 (s, 2H, CH2Cl); ıC (100.91 MHz; CDCl3) 34.9, 128.2,
128.9, 130.1, 130.7, 137.2, 152.4, 192.3; GC–MS tR = 18.69 min m/z
182 (M+ +2, 33), 180 (M+, 75), 179 (90), 145 (25), 115 (100), 91 (25).
(Z)-2-(Chloromethyl)-3-(4-chlorophenyl)acrylaldehyde ((Z)-9).
Yield 70%; ıH (400 MHz; CDCl3) 9.59 (1H, s, CHO), 7.61 (2H, m,
aromatic hydrogens), 7.48 (2H, m, aromatic hydrogens), 7.41 (1H,
4.2.2. General procedure for the conversion of the Baylis–Hillman
adducts into the corresponding 2-chloromethyl-3-arylacrylates
[31]
The Baylis–Hillman esters (70.0 mmol) were refluxed 3 h in CCl4
(60 mL) with PPh3 (80.0 mmol). The reaction mixture was cooled
to 0 ◦C and the solution was recovered. Diethyl ether (150 mL) was
added and the mixture was scratched until triphenyl phosphine
oxide separated in crystalline form. The mixture was filtered by
suction and the solid was washed with diethyl ether. The combined
organic phase was evaporated to dryness and chromatographed
on a silica gel column with increasing amounts of ethyl acetate in
hexane.
(Z)-Methyl 2-(chloromethyl)-3-phenylacrylate. Yield 90%; spec-
troscopic data for this compound are in agreement with those
reported in literature [32].

100
E. Brenna et al. / Journal of Molecular Catalysis B: Enzymatic 84 (2012) 94–101
s, CH ), 4.39 (2H, s, CH2Cl); ıC (100.91 MHz; CDCl3) 34.7, 129.4,
131.4, 131.8, 137.1, 137.8, 150.8, 192.1; GC–MS tR = 21.34 min m/z
216 (M+ +2, 15), 214 (M+, 25), 179 (100), 151 (30), 115 (100).
COOMe), 3.59 (2H, s, CH2); ıC (100.91 MHz; CDCl3) 37.5, 51.9, 126.4,
128.5, 130.3, 131.2, 137.2, 139.7, 167.1; GC/MS tR 18.74 min, m/z
210 (M+, 67), 179 (29), 150 (100), 115 (100).
(Z)-2-(Chloromethyl)-3-(3-methoxyphenyl)acrylaldehyde
((Z)-
Methyl 2-(3-methoxybenzyl)acrylate. Yield 81%; ıH (400 MHz;
CDCl3) 7.19 (1H, m, aromatic hydrogen), 6.82–6.72 (3H, m, aromatic
hydrogens), 6.23 (1H, m, CHH), 5.48 (1H, m, CHH), 3.78 (3H, s, OMe),
3.73 (3H, s, COOMe), 3.61 (2H, s, CH2); ıC (100.91 MHz; CDCl3) 38.1,
51.8, 55.1, 111.7, 114.7, 121.3, 126.2, 129.3, 139.9, 140.2, 159.6,
167.2; GC/MS tR 19.53 min, m/z 206 (M+, 50), 174 (24), 146 (100).
10). Yield 91%; ıH (400 MHz; CDCl3) 9.58(1H, s, CHO), 7.43 (s, 1H,
CH ), 7.40 (1H, t, J 8.4 Hz, aromatic hydrogen), 7.23–7.21 (2H, m,
aromatic hydrogens), 7.02–7.01 (1H, m, aromatic hydrogens), 4.41
(2H, s, CH2Cl), 3.86 (3H, s, OMe); ıC (100.91 MHz; CDCl3) 35.1,
55.3, 114.9, 116.9, 122.6, 130.1, 134.6, 137.6, 152.4, 159.9, 192.3;
GC–MS tR = min 21.92 min m/z 212 (M+ +2, 20), 210 (M+, 60), 179
(40), 147 (100), 131 (35), 115 (45), 91 (10).
4.3.3. General procedure for the conversion of the substituted
benzylacrylates into the corresponding substituted
4.3. Synthesis of substituted benzylacrylaldehydes 7, 11, and 12
benzylpropenols
The reduction of substituted benzylacrylates to substituted ben-
zylpropenols was performed according to procedure 4.2.3.
2-(4-Chlorobenzyl)prop-2-en-1-ol. Yield 68%; ıH (400 MHz;
CDCl3) 7.22 (2H, m, aromatic hydrogens), 7.08 (2H, m, aromatic
hydrogens), 5.08 (1H, m, CHH ), 4.83 (1H, m, CHH ), 3.95 (2H, s,
CH2OH), 3.31 (2H, s, CH2Ar); ıC (100.91 MHz; CDCl3) 38.9, 64.8,
111.7, 128.4, 130.2, 131.9, 137.4, 147.5; GC/MS tR 18.10 min, m/z
182 (M+, 5), 164 (7), 129 (100), 115 (20).
2-(3-Methoxybenzyl)prop-2-en-1-ol. Yield 72%; ıH (400 MHz;
CDCl3) 7.19 (1H, m, aromatic hydrogen), 6.82–6.72 (3H, m, aro-
matic hydrogens), 5.12 (1H, m, CHH), 4.91 (1H, m, CHH), 4.03 (2H,
s, CH2OH), 3.78 (3H, s, OMe), 3.38 (2H, s, CH2Ar); ıC (100.91 MHz;
CDCl3) 39.9, 55.1, 65.2, 111.5, 111.6, 114.6, 121.3, 129.3, 140.6,
147.9, 159.7; GC/MS tR 18.84 min, m/z 178 (M+, 100), 159 (27), 121
(67).
Benzylacrylaldehyde 7 was prepared following the synthetic
sequence described in Ref. [25]. Aldehydes 11, and 12 were pre-
pared according to the following path: the suitable Baylis–Hillman
adduct obtained by reaction of the aromatic aldehyde with
methyl acrylate in the presence of DABCO (according to procedure
4.2.1) was submitted to HBr rearrangement. The correspond-
ing 2-bromomethyl-3-arylacrylates were treated with DABCO and
NaBH4 to afford substituted benzylacrylates which were reduced
to the corresponding propenols. These latter substrates gave the
corresponding substituted benzylacrylaldehydes by MnO2 oxida-
tion.
4.3.1. General procedure for the conversion of the Baylis–Hillman
adducts into the corresponding 2-bromomethyl-3-arylacrylates
[34]
To a stirred solution of the suitable Baylis–Hillman adduct
(80 mmol) in CH2Cl2 (150 mL) was added dropwise HBr 48% (26 mL)
and then concentrated H2SO4 (23.2 mL) at 0 ◦C. After stirring
overnight at r.t., the reaction mixture was carefully diluted with
CH2Cl2 and water. The mixture was extracted with CH2Cl2; the
organic phase was washed twice with water, dried (Na2SO4), and
concentrated under reduced pressure, to give a residue which was
chromatographed on a silica gel column with increasing amounts
of ethyl acetate in hexane.
(Z)-Methyl 2-(bromomethyl)-3-(4-chlorophenyl)acrylate. Yield
71%; ıH (400 MHz; CDCl3) 7.76 (1H, s, CH ), 7.51 (2H, m, aro-
matic hydrogens), 7.43 (2H, m, aromatic hydrogens), 4.35 (2H, s,
CH2Brl), 3.88 (3H, s, COOMe); ıC (100.91 MHz; CDCl3) 26.2, 52.5,
129.2, 130.9, 131.2, 131.6, 132.6, 141.5, 166.3; GC/MS tR 23.51 min,
m/z 288 (M+, 6), 209 (100), 149 (75), 115 (87).
(Z)-Methyl 2-(bromomethyl)-3-(3-methoxyphenyl)acrylate. Yield
76%; ıH (400 MHz; CDCl3) 7.80 (1H, s, CH ), 7.35 (1H, m, aromatic
hydrogen), 7,15 (2H, m, aromatic hydrogens), 6.97 (1H, m, aro-
matic hydrogen), 4.40 (2H, s, CH2Br), 3.87 (3H, s, OMe), 3.85 (3H,
s, COOMe); ıC (100.91 MHz; CDCl3) 26.8, 52.4, 55.3, 114.2, 115.8,
122.0, 128.8, 129.8, 135.5, 142.9, 159.8, 166.5; GC/MS tR 23.95 min,
m/z 284 (M+, 14), 205 (68), 145(100).
4.3.4. General procedure for the conversion of the substituted
substituted benzylpropenols into the corresponding substituted
benzylacrylaldehydes
The oxidation of substituted benzylpropenols to substituted
benzylacrylaldehydes was performed according to procedure 4.2.4.
2-(4-Chlorobenzyl)acrylaldehyde (11). Yield 65%; ıH (400 MHz;
CDCl3) 9.57 (1H, s, CHO), 7.24 (2H, m, aromatic hydrogens), 7.10
(2H, m, aromatic hydrogens), 6.11 (1H, m, CHH ), 6.06 (1H, m,
CHH ), 3.52 (2H, s, CH2Ar); ıC (100.91 MHz; CDCl3) 33.5, 128.6,
130.43, 132.2, 135.1, 136.6, 149.2, 193.6; GC/MS tR 16.3 min, m/z
180 (M+, 11), 145 (100), 125 (15), 115 (56).
2-(3-Methoxybenzyl)acrylaldehyde (12). Yield 64%; ıH (400 MHz;
CDCl3) 9.60 (1H, s, CHO), 7.20 (1H, m, aromatic hydrogen),
6.80–6.68 (3H, m, aromatic hydrogens), 6.11 (1H, m, CHH), 6.06 (1H,
m, CHH), 3.78 (3H, s, OMe), 3.53 (2H, s, CH2Ar); ıC (100.91 MHz;
CDCl3) 34.1, 55.1, 111.8, 114.9, 121.5, 129.5, 135.1, 139.7, 149.6,
159.8, 193.9; GC/MS tR 17.42 min, m/z 176 (M+, 100), 145 (33), 108
(40).
4.4. General procedure for Baker’s Yeast reduction of aldehydes
(a) Substrate adsorbed on the resin (for aldehydes (Z)-6, (Z)-9,
(Z)-10, 7, 11, and 12). A mixture of 100 g of Baker’s Yeast (Lesaf-
fre) and 50 g of d-glucose in 1 L of tap water was prepared. After
30 min stirring at 30 ◦C the aldehyde (2.5 g) adsorbed on 37.5 g of
hydrophobic resins (polystyrene XAD-1180N) was added within
10 min. The mixture was kept under stirring 48 h at r.t. and then fil-
tered on a cotton plug. The collected mass was washed repeatedly
with tap water to remove most of the cells. The resin was then col-
lected and extracted twice in sequence with acetone (200 mL) and
ethyl acetate (200 mL). The organic phase was concentrated to 1/3
and then washed with brine. The residue obtained upon evapora-
tion of the dried (Na2SO4) extract was chromatographed on a silica
gel column with increasing amounts of ethyl acetate in hexane.
(b) Substrate Added in Solution (for aldehydes (Z)-6, (Z)-9, (Z)-10,
and (E)-14). To the fermenting yeast mixture described above (100 g
yeast) the suitable aldehyde (2.5 g) dissolved in 25 mL of ethanol
4.3.2. General procedure for the conversion of the
2-bromomethyl-3-arylacrylates into the corresponding
substituted benzylacrylates [35]
The bromomethylacrylate (60 mmol) was dissolved in 1:1
THF/water (60 mL) and treated with DABCO (60 mmol). After stir-
ring 15 min at r.t., NaBH4 (60 mmol) was added. After 15 min,
the reaction mixture was poured in HCl 1 M, and extracted with
ethyl acetate. The organic phase was washed with water, dried
(Na2SO4), and concentrated under reduced pressure to give a
residue which was chromatographed on a silica gel column with
increasing amounts of ethyl acetate in hexane.
Methyl 2-(4-chlorobenzyl)acrylate. Yield 85%; ıH (400 MHz;
CDCl3) 7.25 (2H, m, aromatic hydrogens), 7.13 (2H, m, aromatic
hydrogens), 6.23 (1H, m, CHH ), 5.48 (1H, m, CHH ), 3.73 (3H, s,

E. Brenna et al. / Journal of Molecular Catalysis B: Enzymatic 84 (2012) 94–101
101
was added dropwise within 10 min. After 48 h stirring, acetone (1 L)
was added to the mixture. After stirring overnight, ethyl acetate
(1 L) was added and the mixture was stirred 1 h. The two phases
were separated in a separatory funnel and the aqueous phase was
extracted twice with a 9:1 mixture of ethyl acetate-hexane. The
combined organic phase was concentrated under vacuum to a
small volume. After addition of 10 vol of ethyl acetate–hexane 9:1,
the organic phase was washed repeatedly with water and brine.
The oily residue obtained upon evaporation of the dried (Na2SO4)
organic phase was chromatographed on a silica gel column obtain-
ing with ca. 15–20% ethyl acetate in hexane the saturated alcohols
2, 15 and 16 and with neat ethyl acetate the diols 17, 18 and 19.
Deuterium Incorporation Experiments. The reactions were carried
out exactly as described above, with the only modification that ca.
1% of 99% D2O was added at the beginning to the reaction mixture.
(R)-2-Methyl-3-phenylpropan-1-ol ((R)-2). ıH (400 MHz; CDCl3):
7.33–7.10 (5H, m, aromatic hydrogens), 3.51 (1H, dd, J 5.8 and
10.6 Hz, CHHOH), 3.45 (1H, dd, J 5.8 and 10.3 Hz, CHHOH), 2.75
(1H, dd, J 6.4 and 13.5 Hz, PhCHH), 2.40 (1H, dd, J = 8.0 and 13.5 Hz,
PhCHH), 1.93 (1H, m, CHCH3), 0.90 (3H, d, J 6.7 Hz, CH3). ıC
(100.91 MHz; CDCl3): 16.3, 37.6, 39.6, 67.5, 125.8, 128.2, 129.1,
140.6. The material recovered (33% isolation yields) from the reduc-
tion of (Z)-6 loaded on the resin showed [␣]D =+10.9 (c 1.22,
CHCl3) with ee = 99% [lit. Ref. [36]: [␣]D = −10. (c 0.84, CHCl3) for
the (S) enantiomer (ee = 87%)]. The material recovered (45% isola-
tion yields) from the reduction of 7 loaded on the resin showed
[␣]D = +10.4 (c 1.22, CHCl3).
ıH (400 MHz; CDCl3): 7.30 (m, 4H, aromatic hydrogens), 6.29 (1H,
s, PhCHOAc)), 5.34 (1H, s, CH), 5.31 (1H, s, CH), 4.58 (1H, d, J
13.5, CHOAc), 4.42 (1H, d, J 13.2, CHOAc). ıC (100.91 MHz; CDCl3;
Me4Si): 21.1, 21.4, 64.3, 75.1, 116.3, 129.0, 129.1, 134.7, 136.6,
142.2, 169.9, 170.7.
2-(1-hydroxy-1-(3-methoxy-phenyl))-methyl-prop-2-en-1-ol
(12). Yield 6%. ıH (500 MHz; C6D6): 7.09 (2H, m, aromatic hydro-
gens), 6.94 (1H, m, aromatic hydrogens), 6.72 (1H, m, aromatic
hydrogens), 5.14 (1H, s, ArCHOH)), 5.10 (1H, br s, CHH), 5.05 (1H,
br s, CHH), 4.00 (1H, d, J 13.4 Hz, CHHOH), 3.82 (1H, d, J 13.4 Hz,
CHHOH), 3.35 (3H, s, OCH3); ıD (75.77 MHz; C6H6;) 4.01 (CDHOH),
4.85 (CHDOH), 3.36 (OCH2D) (see Fig. 2b); ␦C (100.91 MHz, CDCl3):
55.2, 63.9, 76.2, 111.8, 113.2, 113.5, 118.6, 129.5, 143.5, 149.3,
159.8.
References
[1] D. Seebach, H.-O. Kalinowski, Nachr. Chem. Tech. Lab. 24 (1976) 25.
[2] C. Fuganti, Pure Appl. Chem. 62 (1990) 1449–1452.
[3] R. Csuk, B.I. Glaenzer, Chem. Rev. 91 (1991) 49–97;
B. Pscheidt, A. Glieder, Microb. Cell Factories 7 (2008) 25.
[4] E. Brenna, F.G. Gatti, A. Manfredi, D. Monti, F. Parmeggiani, Org. Process Res.
Dev. 16 (2012) 262–268;
M. Bechtold, E. Brenna, C. Femmer, F.G. Gatti, S. Panke, F. Parmeggiani, A. Sac-
chetti, Org. Process Res. Dev. 16 (2012) 269–276.
[5] R. Bernardi, R. Cardillo, D. Ghiringhelli, J. Chem. Soc. Chem. Commun. (1984)
460–461.
[6] G. Tuynenburg Muys, B. van der Ven, A.P. de Jonge, Nature 194 (1962) 995–996.
[7] H. Akita, A. Furuichi, H.K. Oshiji, K. Horikoshi, T. Oishi, Tetrahedron Lett. 23
(1982) 4051–4054.
[8] B. Wipf, E. Kupfer, R. Bertazzi, H.G.W. Leuenberger, Helv. Chim. Acta 66 (1983)
485–488.
(R)-2-Methyl-3-(4-chloro-phenyl)propan-1-ol
((R)-15).
ıH
(400 MHz; CDCl3): 7.40–7.05 (5H, m, aromatic hydrogens), 3.49
(2H, m, CH2OH), 2.75 (1H, dd, J 6.1 and 13.5 Hz, ArCHH), 2.39
(1H, dd, J 8.3 and 13.5 Hz, ArCHH), 1.91 (1H, m, CHCH3), 0.90 (3H,
d, J 6.7 Hz, CH3); ıC (100.91 MHz; CDCl3): 16.2, 37.6, 38.9, 67.4,
128.3, 130.5, 131.7, 139.0. The material recovered (15% isolation
yields) from the reduction of (Z)-9 loaded on the resin showed
[␣]D = +11.5 (c 3.5, CHCl3), with ee = 96%. The material recovered
(20% isolations yields) from the reduction of 11 loaded on the resin
showed [␣]D = +8.4 (c 3.0, CHCl3), with ee = 69%.
(R)-2-Methyl-3-(3-methoxy-phenyl)propan-1-ol ((R)-16). ıH
(500 MHz; CDCl3): 7.21 (1H, m, aromatic hydrogens), 6.79–6.71
(3H, m, aromatic hydrogens), 3.81 (3H, s, OCH3), 3.54 (1H,dd, J
10.5 and 5.8 Hz, CHHOH), 3.49 (1H, dd, J 10.5 and 6.0 Hz, CHHOH),
2.74 (1H, dd, J 6.5 and 13.5 Hz, ArCHH), 2.42 (1H, dd, J 7.9 and
13.5 Hz, ArCHH), 1.96 (1H, m, CHCH3), 0.94 (3H, d, J 6.8, CH3); ıD
(75.77 MHz, CHCl3): 3.81 (OCH2D), 3.54 (CDHOH), 2.75 (PhCDH),
0.94 (CH2D) (major isomer); 3.50 (CHDOH), 2.42 (PhCHD) (minor
isomer) (see Fig. 1c); ıC (100.91 MHz; CDCl3):16.4, 37.6, 39.8, 55.1,
67.6, 111.1, 114.9, 121.6, 129.1, 142.3, 159.6. The material recov-
ered (13% isolation yields) from the reduction of (Z)-10 loaded on
the resin showed [␣]D = +10.1 (c 1.1, CHCl3) with ee = 98% (HPLC).
The material recovered (19% isolation yields) from the reduction
of 12 loaded on the resin showed [␣]D = +9.4 (c 1.02, CHCl3) with
ee = 94% (HPLC). The material recovered (32% isolation yields) from
the reduction of (E)-15 dissolved in ethanol showed [␣]D = −5.7 (c
1.05, CHCl3) with ee = 54% (HPLC).
[9] B. Zhou, A.S. Gopalan, F. VanMiddlesworth, W.-R. Shieh, C. Sih, J. Am. Chem. Soc.
105 (1983) 5925.
[10] M. Utaka, S. Konishi, A. Mizouka, T. Ohkubo, T. Sakai, S. Tsuboi, A. Takeda, J. Org.
Chem. 54 (1989) 4989–4992.
[11] E. Brenna, G. Fronza, C. Fuganti, D. Monti, F. Parmeggiani, J. Mol. Cat. B: Enzym.
73 (2011) 17–21.
[12] M. Hall, C. Stueckler, B. Hauer, R. Stuermer, T. Friedrich, M. Breuer, W. Kroutil,
K. Faber, Eur. J. Org. Chem. (2007) 1511–1516.
[13] G. Fronza, C. Fuganti, S. Serra, Eur. J. Org. Chem (2009) 6160–6171.
[14] C. Fuganti, P. Grasselli, S. Servi, J. Chem. Soc. Perkin Trans. I (1983) 241–244.
[15] C. Fuganti, P. Grasselli, Chem. Ind. (Lond.) (1977) 983.
[16] E. Brenna, F.G. Gatti, D. Monti, F. Parmeggiani, A. Sacchetti, Chem. Commun. 48
(2012) 79–81.
[17] J. Wrobel, J. Millen, J. Sredy, A. Dietrich, B.J. Gorham, M. Malamas, J.M. Kelly,
J.G. Bauman, M.C. Harrison, L.R. Jones, C. Guinosso, K. Sestanj, J. Med. Chem. 34
(1991) 2504–2520.
[18] E. Brenna, F.G. Gatti, D. Monti, F. Parmeggiani, S. Serra, Adv. Synth. Catal. 354
(2012) 105–112.
[19] H. Simon, M. Kellner, H. Guenther, Angew. Chem. Int. Ed. 12 (1973) 146.
[20] C. Fuganti, D. Ghiringhelli, P. Grasselli, J. Chem. Soc. Chem. Commun. (1975)
846–847.
[21] H. Gerlach, B. Zagalak, J. Chem. Soc. Chem. Commun. (1973) 274–275.
[22] C. Fuganti, P. Grasselli, G. Poli, S. Servi, A. Zorzella, J. Chem. Soc. Chem. Commun.
(1988) 1619–1621.
[23] E.J. Corey, G.N. Widiger, J. Org. Chem. 40 (1975) 2975–2976.
[24] G. Fronza, C. Fuganti, P. Grasselli, G. Poli, S. Servi, J. Org. Chem. 53 (1988)
6153–6154.
[25] P. Ferraboschi, S. Reza-Elahi, E. Verza, E. Santaniello, Tetrahedron: Asymm. 10
(1999) 2639–2642.
ˇ
[26] V. Sunjic´, M. Majeric´, Z. Hamersˆak, Croat. Chem. Acta 69 (1996) 643–660.
[27] H. Huschmann, W. Strassburger, E. Friderichs, EP 0693475 A1, 1996.
[28] K. Biswas, C. Boerner, J. Gimeno, P.J. Goldsmith, D. Ramazzotti, A.L. So, S. Wood-
ward, Tetrahedron 61 (2005) 1433–1442.
[29] X. Feng, Y.Q. Yuan, H.L. Cui, K. Jiang, Y.C. Chen, Org. Biomol. Chem. 7 (2009)
3660–3662.
[30] I. Shiina, Y. Yamai, T. Shimazaki, J. Org. Chem. 70 (2005) 8103–8106.
[31] B. Das, B.S. Ksanth, K.R. Reddy, G. Satyalakshmi, R.A. Kumar, Chem. Lett. 37
(2008) 512–513.
2-(1-Hydroxy-1-phenyl)methyl-prop-2-en-1-ol (17). Yield 15%.
ıH (400 MHz; CDCl3): 7.40–7.23 (m, 5H, aromatic hydrogens), 5.35
(1H, s, PhCHOH)), 5.21 (2H, s, CH2), 4.14 (1H, d, J 13.2 Hz, CHOH),
4.04 (1H, d, J 13.2 Hz, CHOH). ıC (100.91 MHz; CDCl3; Me4Si): 64.0,
76.3, 113.4, 126.3, 127.7, 128.4, 141.8, 149.3.
2-(1-hydroxy-1-(4-chloro-phenyl))methyl-prop-2-en-1-ol (18).
Yield 8%. It was purified and characterised as the corresponding
diacetate, prepared by reaction with acetic anhydride in pyridine.
[32] A. Bouzide, Org. Lett. 4 (2002) 1347–1350.
[33] J.C. Depezay, Y. Le Merrer, Tetrahedron Lett. (1974) 2751–2754.
[34] R. Buchholtz, H.M.R. Hoffmann, Helv. Chim. Acta 74 (1991) 1213–1220.
[35] D. Basavaiah, N. Kumaragurubaran, Tetrahedron Lett. 42 (2001) 477–479.
[36] P.C. Hutchison, T.D. Heightman, D.J. Procter, J. Org. Chem. 69 (2004) 790–801.