Lentinus strigellus: a new versatile stereoselective biocatalyst for the bioreduction of prochiral ketones Bartholomeu A. Barros-Filho a , Maria da Conceição F. de Oliveira a, * , Telma L. G. Lemos a , Marcos C. de Mattos a , Gonzalo de Gonzalo b , Vicente Gotor-Fernández b , Vicente Gotor b, * a Departamento de Química Orgânica e Inorgânica, Laboratório de Biotecnologia e Síntese Orgânica (LABS), Universidade Federal do Ceará, Campus do Pici, Caixa Postal 6044, Fortaleza, Ceará 60455-970, Brazil b Departamento de Química Orgánica e Inorgánica, Instituto Universitario de Biotecnología de Asturias, Universidad de Oviedo, c/Julián Clavería 8, 33006 Oviedo, Spain article info Article history: Received 2 February 2009 Accepted 10 February 2009 Available online 11 March 2009 abstract Growing cells of the basiodiomycete Lentinus strigellus in potato-dextrose broth have been used for the first time as a biocatalyst in the stereoselective reduction of aromatic and aliphatic ketones. Most of the aromatic ketones were converted into the corresponding optically active alcohols in up to >99% enan- tiomeric excess under very mild reaction conditions. Among the aliphatic ketones tested, 2-octanone was enzymatically reduced by this microorganism to enantiopure (S)-2-octanol with almost complete conversion. Ó 2009 Elsevier Ltd. All rights reserved. 1. Introduction Nowadays, the fine chemical, pharmaceutical, and agrochemical industries are demanding the production of optically active com- pounds. Chiral alcohols are of great importance to the industrial sector, since these products are normally bioactive compounds and adequate precursors for the synthesis of more complex struc- tures. 1 The asymmetric reduction of prochiral ketones is the most straightforward way to prepare the desired enantiomerically en- riched alcohols and traditionally two different approaches have been described: catalytic asymmetric hydrogenation using chiral organometallic complexes 2 or bioreduction reactions catalyzed by oxidoreductases. 3 Both of them have the advantage that opti- cally active alcohols can be theoretically recovered in 100% yield. Besides well-known chemical methodologies, biocatalytic ap- proaches have gained much attention since they constitute a more environmentally friendly alternative. During the last few years, the development of novel biocatalytic processes has attracted an increasing interest in the field of organic chemistry due to the dis- covery of new enzymes from Nature or wild-type biocatalysts. 4 This fact has presented biocatalysis as an ideal tool for the produc- tion of a wide range of optically active products, which can often be obtained under very mild reaction conditions and in high enantio- meric excesses. In this context, whole-cells from microorganisms and vegetables have been established as efficient biocatalyst in the bioreduction of prochiral ketones. 5 As part of our ongoing project in the identification, analysis, and application of novel biocatalysts from the Brazilian biodiversity, 6 herein we report an investigation of the basidiomycete Lentinus strigellus as reducing agent of aromatic and aliphatic prochiral ke- tones to the corresponding chiral alcohols. This edible and medic- inal mushroom is found in certain parts of South America, and has been reported as a source of bioactive polysaccharides. 7 This is the first report of this fungus as a biocatalyst in organic reactions. 2. Results and discussion A set of aromatic 1–10a (Scheme 1) and aliphatic 11–14a (Scheme 2) ketones was reduced by growing cells of L. strigellus in potato-dextrose broth. Enzymatic reductions of each prochiral 0957-4166/$ - see front matter Ó 2009 Elsevier Ltd. All rights reserved. doi:10.1016/j.tetasy.2009.02.008 * Corresponding authors. Tel.: +34 985 103448; fax: +34 985 103448 (V.G.), tel.: +55 8533669441; fax: +55 8533669782 (M.C.F.O.). E-mail addresses: mcfo@ufc.br (M. C. F. de Oliveira), vgs@fq.uniovi.es (V. Gotor). O R 2 R 3 R 4 R 1 OH R 2 R 3 R 4 R 1 Lentinus strigellus Potato Dextrose medium 28 °C/ 200 rpm 1-10a (S)-1-8b (R)-9-10b 1 R 1 =H R 2 =H R 3 =H R 4 =H 2 R 1 =H R 2 =OMe R 3 =H R 4 =H 3 R 1 =H R 2 =NO 2 R 3 =H R 4 =H 4 R 1 =H R 2 =H R 3 =OMe R 4 =H 5 R 1 =H R 2 =H R 3 =NO 2 R 4 =H 6 R 1 =H R 2 =H R 3 =H R 4 =OMe 7 R 1 =H R 2 =H R 3 =H R 4 =NO 2 8 R 1 =H R 2 =H R 3 =H R 4 =Me 9 R 1 =Cl R 2 =H R 3 =H R 4 =H 10 R 1 =Cl R 2 =H R 3 =Cl R 4 =Cl * Scheme 1. Bioreduction of prochiral aromatic ketones using Lentinus strigellus. Tetrahedron: Asymmetry 20 (2009) 1057–1061 Contents lists available at ScienceDirect Tetrahedron: Asymmetry journal homepage: www.elsevier.com/locate/tetasy