the efficient synthesis of an illustrative pharmaceutically relevant
compound has been demonstrated. Our methodology should be
applicable in the synthesis of a range of analogous enantiopure
lactams and g-amino acids.
Among the anaerobic microorganisms tested for cinnamate
reductase activity in this study, none catalysed the formation of the
(R)-enantiomer. The opposite stereochemical course of the reac-
tion could be obtained by identifying an enzyme/microorganism
that catalyses the formation of the opposite enantiomer5–7 or,
as recently demonstrated, stereocomplementary variants of the
enzyme can be obtained by a protein engineering strategy.17
Screening for the organisms and enzymes possessing opposite
stereoselectivity, as well as studies on the extended substrate
specificity, are ongoing in our laboratory.
5 R. Stuermer, B. Hauer, M. Hall and K. Faber, Curr. Opin. Chem. Biol.,
2007, 11, 203–213.
6 B. Kosjek, F. J. Fleitz, P. G. Dormer, J. T. Kuethe and P. N. Devine,
Tetrahedron: Asymmetry, 2008, 19, 1403–1406.
7 (a) M. Hall, C. Stueckler, W. Kroutil, P. Macheroux and K. Faber,
Angew. Chem., Int. Ed., 2007, 46, 3934–3937; (b) M. Hall, C. Stueckler,
H. Ehammer, E. Pointner, G. Oberdorfer, K. Gruber, B. Hauer, R.
Stuermer, W. Kroutil, P. Macheroux and K. Faber, Adv. Synth. Catal.,
2008, 350, 411–418; (c) A. Mu¨ller, B. Hauer and B. Rosche, Biotechnol.
Bioeng., 2007, 98, 22–29; (d) A. Mu¨ller, R. Sturmer, B. Hauer and
B. Rosche, Angew. Chem., Int. Ed., 2007, 46, 3316–3318; (e) D. J.
Bougioukou and J. D. Stewart, J. Am. Chem. Soc., 2008, 130, 7655–
7658; (f) M. A. Swiderska and J. D. Stewart, Org. Lett., 2006, 8, 6131–
6133; (g) J. F. Chaparro-Riggers, T. A. Rogers, E. Vazquez-Figueroa,
K. M. Polizzi and A. S. Bommarius, Adv. Synth. Catal., 2007, 349,
1521–1531; (h) H. S. Toogood, A. Fryszkowska, V. Hare, K. Fisher,
A. Roujeinikova, D. Leys, J. M. Gardiner, G. M. Stephens and N. S.
Scrutton, Adv. Synth. Catal., 2008, 350, 2789–2803.
8 A. Fryszkowska, H. Toogood, M. Sakuma, J. M. Gardiner,
G. M. Stephens and N. Scrutton, Adv. Synth. Catal., 2009,
DOI: 10.1002/adsc.200900574.
Conclusions
9 B. V. Adalbjo¨rnsson, H. S. Toogood, A. Fryszkowska, C. R. Pudney,
T. A. Jowitt, D. Leys and N. S. Scrutton, ChemBioChem, 2009,
DOI: 10.1002/cbic.200900570.
We have developed a short, high-yielding preparative method for
the synthesis of chiral b-aryl-b-cyano-propanoic acid derivatives
with high optical purity. This is also the first example of
chemoselective and highly enantioselective reduction of b-aryl-b-
cyano-propanoic acid derivatives (up to >99% ee) using organisms
possessing ‘ene’ reductase activity. Our approach can be applied to
the synthesis of b-aryl substituted g-aminobutyric acid derivatives,
like baclofen 7, in good overall yields and high enantiopurity. The
synthetic strategy is convenient and much shorter than many other
synthetic methods for the production of GABA derivatives.1
10 H. Giesel, G. Machacek, J. Bayerl and H. Simon, FEBS Lett., 1981,
123, 107–110.
11 H. Korbekandi, P. Mather, J. M. Gardiner and G. M. Stephens, Enzyme
Microb. Technol., 2008, 42, 308–314.
12 (a) E. T. Davies and G. M. Stephens, Appl. Microbiol. Biotechnol., 1996,
46, 615–618; (b) F. Foroughi, P. Williams and G. M. Stephens, Enzyme
Microb. Technol., 2006, 39, 1066–1071.
13 Total protein concentration of crude extracts was determined to be: for
C. sporogenes: 36 mg mL-1; for Acetobacterium woodii: 10.7 mg mL-1
and for Ruminococcus productus: 5.8 mg mL-1.
14 Typical experimental procedure for analytical assays: salt 2 (0.09 mmol),
NADH (0.10 mmol, 76 mg), crude extracts of C. sporogenes, R.
productus and A. woodii (1 mL), phosphate buffer (20 mL, 50 mM,
pH 7.0) were incubated under H2 atmosphere at 30 ◦C for 3 days.
The reactions were monitored by GC (conversion) and HPLC (ee,
Chiralcel OD), after acidification and derivatization of the product
and unreacted substrate to their respective methyl esters 5, using
Notes and references
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M. Larcheveque, Synlett, 1999, 1118–1120.
a
(trimethylsilyl)diazomethane solution (2 M in hexanes). For
0.7–1 mmol scale experiments, all the reaction components were used
proportionally.
15 After prolonged incubation (up to 6 days) the products 3a–c were seen
to undergo racemisation at a rate of approximately 1–2% ee loss per day
at pH 7.0 (see Supplementary Information, Table S1).
16 A. Fryszkowska, K. Fisher, J. M. Gardiner and G. M. Stephens, J. Org.
Chem., 2008, 73, 4295–4298.
17 S. K. Padhi, D. J. Bougioukou and J. D. Stewart, J. Am. Chem. Soc.,
2009, 131, 3271–3280.
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