H. Kojima et al. / Tetrahedron Letters 50 (2009) 7079–7081
7081
Scheme 1. Synthesis of both enantiomers with Nicotiana tabacum var. Samsun NN.
glucose/dark conditions. Thus, in every case, the stereochemical
course of the reduction shifted to give the -alcohols by the high
CO /light conditions and the course was changed to give the
-alcohols by the air/glucose/dark conditions.
The present method indicates that CO is a useful compound for
L
2
D
2
controlling stereoselectivity in biotransformation. Further studies
for clarifying the mechanism of the present system are in progress
in our laboratories. The efficiency enhancement in the current sys-
tems and the use of other plant-cultured cells are challenges for
the future.
References and notes
1.
(a) Nakamura, K.; Matsuda, T. In Asymmetric Organic Synthesis with Enzymes;
Gotor, V., Alfonsa, I., Garcia-Uradiales, E., Eds.; Wiley-VCH GmbH & Co. KGaA:
Weinheim, 2008; pp 193–228; (b) Andrade, L. H.; Nakamura, K. In Handbook of
Green Chemistry—Green Catalysis; Anastas, P., Ed.; Wiley-VCH, 2008; pp 151–
Figure 2. The
2
L% of products 2a–e. Conditions: air/dark (j); high CO /light (h); air/
glucose/dark ( ).
169; (c) Matsuda, T.; Yamanaka, R.; Nakamura, K. Tetrahedron: Asymmetry
2009, 20, 513.
2
3
4
.
.
.
Ishihara, K.; Hamada, H.; Hirata, T.; Nakajima, N. J. Mol. Catal. B: Enzym. 2003,
3, 145.
Nicotioana tabacum var. Samsun NN photoautotrophic cells were used: Yamada,
Y.; Sato, F. Plant Cell Physiol. 1979, 20, 193.
of L-alcohols was obtained under dark conditions and high L-selec-
tivity was found under light conditions. Photosynthesis will be
largely participating in the present stereochemical control since
2
Conditions at a high atmospheric CO
2
concentration were attained by placing
addition of 3-(3,4-dichlorophenyl)-1,1-dimethylurea (DCMU)
the buffer containing 2 M K CO /2 M KHCO
2
3
3
(1:4, v/v)12 in other wells. A part of
À6
(
1 Â 10 M), a photosynthetic electron transport inhibitor, low-
gas in the culture cluster was taken up by a syringe and the CO
was determined by measuring its IR spectrum (2361 cm ) and by comparing
the spectrum with that of the standard sample: the concentration of
2
concentration
À1
ered the enantioselectivity of the reduction of 1a even under light
conditions: 33% ee of -2a was observed. However, sugars, which
L
atmospheric CO
2 2
in the box was 1.54%. The CO concentration of global
are well-known products of photosynthesis, are not the candidates
because the reaction with glucose shifted the reduction course to
atmosphere is 0.03%.
5. Fluorescent light (HITACHI FL40SW, 400–700 nm, max 580 nm, 30–35 lmol
À2 À1
photons m
s ).
the
gave the similar effect to that of glucose on the enantioselectivity
of the reduction of 1a (1% starch: 2a, 71% ee ( )).
D-selectivity, not to the L-selectivity, and addition of starch
6. D-L notation was adopted here since methyl and trifluoromethyl ketones were
used in this Letter and (R)-configuration of (R)-1-phenyl-2,2,2-trifluoroethanol
is the same configuration as (S)-1-phenylethanol by definition.
D
Addition of fatty acids to the system was examined but stereo-
chemical course of the reductions was not affected by low fatty
acid concentrations and the cells were damaged at high fatty acid
7. Pre-sterilized 12-well cell culture clusters (Corning Incorporated, NY) was used
for pre-cultivation and also for reaction of the ketone. In clean bench, culture
cells (240 mg in 2 mL LS medium) were put in the wells and pre-cultivated for
5
days. The substrate (1 mg in 10
l
L DMSO) was added and the reaction was
/light were as follows: the CO
concentrations. Thus the mechanism of the effect of CO
2
on enan-
carried out for 24 h. Conditions for the high CO
2
2
concentration was 1.54% (v/v) in the absence of glucose; 30–35
l
2
mol photons
tioselective reduction which shifted the reaction course toward the
À2 À1
m
s . Conditions for the air/glucose/dark were as follows: CO (0.03%, v/v);
L-selectivity is obscure in the present time.
glucose (1%, v/v); under dark conditions. The reaction mixture was extracted
with ether. The chemical yields and ee were obtained from GC-analysis using a
Varian Chirasil-DEX-CB (25 m  0.32 mm) column (100 °C isotherm). The
As described above, the addition of glucose changed the stere-
oselectivity toward giving the D-alcohol. To clarify the effect of glu-
retention times of ketone 2a, the L-alcohol, and the D-alcohol were 1.64 min,
1
1
cose, photosynthetic activities were measured using PAM. As the
result, maximum photochemical efficiencies were decreased in the
presence of glucose. Thus, addition of glucose resulted in lowering
photosynthetic activities. While conditions at high photosynthetic
7.89 min, and 8.28 min, respectively.
8. Average data for more than 3–5 times.
9.
(a) Nakamura, K.; Yamanaka, R. Tetrahedron: Asymmetry 2002, 13, 2529; (b)
Nakamura, K.; Yamanaka, R. J. Chem. Soc.. Chem. Commun 2002, 1782.
1
1
0. Biochemistry and Molecular Biology of Plants; Buchanan, B. B., Gruissem, W.,
activities gave the
L-alcohol in high ee, addition of glucose inhib-
Jones, R. L., Eds.; American Society of Plant Physiologists: Merryland, USA,
2
000; Chapter 2, pp 568–628.
1. PAM: pulse amplitude modulation fluorometer (PAM200, Walz Corporation,
Effeltrich, Germany). Minimum chlorophyll fluorescence (F ) and maximum
chlorophyll fluorescence (Fm) were measured after 30 min dark adaptation. The
variable chlorophyll fluorescence (F ) was calculated from (F –F ) and F /F
ited photosynthesis and decreased the
L-selectivity. Enzymes or
products in metabolic pathway of glucose will participate in the
stereochemical control directly or indirectly.
Trifluoromethyl ketones 1d and 1e were also used as the sub-
strates (Table 1, entries 13–20). The stereochemical courses of
o
v
m
o
v
m
gives an estimate for the maximum photochemical efficiency of PS II. cf.
Schreiber, U.; Hormann, H.; Neubauer, C.; Klughammer, C. Aust. J. Plant Physiol.
the reductions of these substrates also shifted toward the
tivity by the high CO /light conditions. Figure 2 shows the
the products 2a–e in the air/dark, the high CO /light, and the air/
L-selec-
1995, 22, 209.
L
% of
12. (a) Warburg, O.; Krippahl, G. Z. Naturforsch. 1960, 15b, 364; (b) Hüsemann, W.;
Barz, W. Physiol. Plant. 1977, 40, 77.
2
2