Asymmetric reduction of nitroalkenes with baker's yeast

Stereochemical Outcome of the Biocatalysed Reduction of Activated Tetrasubstituted Olefins by Old Yellow Enzymes 1–3

“…[7] The identity and absolute configuration of anti-and syn-4 were established by GC/MS and GC analysis on a chiral stationary phase, respectively, by comparison with a 60/40 mixture of (2R,3R)-4 and (2R,3S)-4, obtained by BY reduction of (E)-2, according to ref. [9] The GC/MS data of the reduced products are as follows: anti-4 t R = …”

“…[7] Nitro derivatives (E)-and (Z)-2 were prepared according to ref. [9] (E)-2-Methyl-3-phenylbut-2-enal…”

“…[2b,8] Thus, we decided to re-investigate the biocatalysed reduction by using isolated OYEs, in order to verify whether the global stereochemical outcome of the reaction was due to a different stereoselectivity of the ERs active in the whole-cell systems, or if it was a characteristic of the bioreduction of this kind of substrate. We also submitted nitroalkenes (E)-and (Z)-2 (Scheme 2) to the same investigation, their BY reductions had been already reported in the literature to occur with low diasteroselectivity, [9] affording the same enantiomers of the two diastereoisomeric nitroalkanes 4. The same authors investigated the stability of the reduction products under fermentation conditions, in order to exclude a contribution to the diastereoisomeric ratio due to the epimerisation of the C a stereogenic centre.…”

Two “classical” Old Yellow Enzymes from Chryseobacterium sp. CA49: Broad substrate specificity of Chr-OYE1 and limited activity of Chr-OYE2

“…The nitro group of 13b can be transformed into a variety of other functional groups [38], and the primary nitroalkanes can also be oxidized to the corresponding carboxylic acids to provide the non-steroidal anti-inflammatory profens [39]. For substrate 14a, only racemic product was obtained, which was most probably due to the mechanism of the enzymatic reduction rather than racemization, since recent work has indicated that the spontaneous racemization of 14b is negligible [22,40] and (S)-14b can be achieved with 70%ee using the crude extract of Clostridium sporogenes [22]. The ynone 17a containing a carbon-carbon triple bond was also well accepted by Chr-OYE1 with a specific activity of 8.2 U/mg, which was higher than that of the corresponding enone 16a (3.73 U/mg).…”

Microbial Stereoselective One-Step Conversion of Diols to Chiral Lactones in Yeast Cultures

“…Therefore, our efforts are currently directed toward employing whole cell cultures of different species of yeast in an extension of the biocatalysts' range in lactone biosynthesis. It is worth mentioning that whole cells of yeast are well known from the reduction of the C=O [28][29][30] and C=C [31][32][33][34][35] bonds, as well as the formation of the C=C [36] bond and hydrolysis activity [37]. In general, reports on oxidation reactions performed by yeasts are quite rare [38,39].…”