M. A. Sortino et al. / Tetrahedron: Asymmetry 20 (2009) 1106–1108
1107
Table 1
Biotransformation of N-phenylmaleimide 1, N-phenyl-2-methylmaleimide 3, and N-phenyl-2,3-dimethylmaleimide 4 by filamentous fungi and yeasts.
Fungal spp.
Voucher sp. N0
Substrate
1
3
4
Prod
Conv (%)
ee (%)
Prod
Conv (%)
ee (%)
Conf
Prod
Conv (%)
ee (%)
Conf
Alternaria alternata
Aspergillus flavus
Aspergillus fumigatus
Aspergillus niger
Fusarium graminearum
Geotrichum candidum
Mucor circinelloides
Neurospora crassa
Penicillium spp
Rhizopus oryzae
Rhodotorula rubra
Saccharomyces cerevisiae
Schizosaccharomyces pombe
Sclerotium bataticola
Trichosporon cutaneum
CEREMIC 172-02
ATCC 9170
ATCC 26934
—
5
5
—
92
96
94
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
6
6
—
98
99
96
—
—
—
—
—
—
—
—
—
—
—
—
—
R
R
—
7
7
7
7
—
—
—
7
—
—
—
—
—
—
—
—
—
>99
>99
>99
—
—
—
—
—
—
—
99
99
96
37
—
—
—
39
—
—
>99
>99
>99
>99
—
—
—
>99
—
—
(R,R)
(R,R)
(R,R)
(R,R)
—
—
—
(R,R)
—
—
ATCC 9029
5
6
R
CEREMIC 170-02
CEREMIC 116-71
CEREMIC 128-09
ATCC 9279
CEREMIC 129-09
CEREMIC 130-09
CEREMIC 131-09
ATCC 9763
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
CEREMIC 132-09
CEREMIC 173-02
CEREMIC 133-09
Time of reaction: 3 days.
Prod: Biotransformation product; Conv.: conversion rate; ee: enantiomeric excess; Conf: absolute configuration; CEREMIC: Reference Center in Mycology, National University
of Rosario, Suipacha 531, Rosario 2000, Argentina; ATCC: American Type Culture Collection (Rockville, USA).
pound 4 has two prochiral centers at C-2 and C-3, giving us the
possibility to examine the ability of fungal strains to discriminate
between enantiotopic faces and also to determine the syn- or
anti-hydrogenation of the double bond.
tions (maleimide 2) prevent the hydrogenation of the double bond
by fungi, while hydrogen atoms or donor substituents at the same
positions (compounds 1, 3, and 4) render the maleimides highly
susceptible to the reduction of the double C–C bond by fungi.
The results showed (Table 1) that after 72-h incubation, malei-
mide 3 was reduced to (R)-(+)-N-phenyl-3-methylsuccinimide
614,18 (conversion rate ranging from 96% to 99%)15 by the three
Aspergillus spp. with a 99% ee. The enantiomeric excesses were
determined by 1H NMR spectroscopy using europium tris [3-(hep-
tafluoropropylhydroxymethylen)-(+)-camphorate [Eu(hfc)3] as a
chiral shift reagent.19,20 The absolute configuration of (+)-6 was
determined by comparison of the sign of the specific rotation with
previous reports.7,8 In turn, maleimide 4 was reduced only to trans-
(R,R)-(+)-N-phenyl-2,3-dimethylsuccinimide 79,21,22 by all Aspergil-
lus spp. (conversion rates = 96–99%) and also by Fusarium grami-
nearum and Penicillium sp. (37% and 39%, respectively).15 The
production of only trans N-phenyl-2,3-dimethylmaleimides is
indicative of an anti-addition of the H to the double bond of malei-
mides by fungi, a clear difference from the cis-product obtained by
catalytic hydrogenation of the double bond. In all cases, the ee was
>99%.19
3. Conclusion
In conclusion, we have found in this work that fungi are effi-
cient biocatalysts for the enantioselective hydrogenation of 2-
and 2,3-methylated-phenyl-maleimides, constituting new efficient
tools for the production of chiral succinimides, which could be
asymmetric synthons for organic synthesis or useful biologically
active compounds.9
The results obtained here are extremely attractive since whole
fungal cells are highly advantageous biocatalysts because of their
rapid growth in natural and synthetic media, their ease of han-
dling, and simple scale-up. They play a leading role in ‘chemo-
enzymatic syntheses’ because of their great diversity which pro-
duces a myriad of useful enzymes with catalytic abilities.23
Acknowledgments
The diastereo- and enantioselective production of pure (+)-7
clearly show that Aspergillus strains possess a high ability not only
for reducing double bonds, but also for discriminating the enantio-
topic faces of dimethylated maleimides. F. graminearum and Peni-
cillium sp. showed a lower capacity for reducing the double
bonds of 4, but showed the same stereoselectivity.
MAS acknowledges CONICET for the doctoral fellowship. SAZ is
grateful to both the Agencia Nacional de Promoción Científica y
Tecnológica de Argentina (ANPCyT) and the National University
of Rosario for grants. VCF acknowledges CNPq (Brazil) and Network
RT 0284 RIBIOFAR (CYTED).
Our results with the filamentous fungi of the genera Aspergillus,
Fusarium, and Penicillium are similar to those obtained by Hirata
et al.7–9 with a cultured suspension of plant cells. They have re-
cently demonstrated that Nicotiana tabacum, Catharanthus roseus,
Parthenocissus tricuspidata, and Cynechococcus sp. possess the
capacity to hydrogenate the double bond of maleimide 1 affording
phenylsuccinimide 5 in 0.5–7 days with Cynechococcus sp. being
the most efficient plant spp. (0.5 days).7,8 In turn, N. tabacum,
Cyinechococcus sp. along with Marchantia polymorpha showed the
ability to hydrogenate the double bond of the pro-chiral N-phe-
nyl-2-methylmaleimide 3 to afford (R)-N-phenyl-3-methylsuccini-
mide 6 with a 99% ee.8 In turn, M. polymorpha enantioselectively
hydrogenated N-phenyl-2,3-dimethylmaleimide 4 to yield trans-
(R, R)-N-phenyl-2,3-dimethylsuccinimide 7 with 99% ee.9
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A comparison of the results obtained with phenylmaleimides 1–
4 suggests that electron-withdrawing substituents on the 2,3-posi-