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Bruni et al. (2002) investigated the reduction of acetophenone and the hydrolysis of 1-acetoxy-2 methylcyclohexene with plants to the corresponding S-carbinol and S-ketone, Scheme 1. Results showed that carrot (Daucus carota) reduced the acetophenone to the pure (S)-1-phenylethanol after 3 days with ee of 100 %. Lower yields were achieved with fenne (Foeniculum vulgare) and marrow (Cucurbita pepo), 37 and 10 %, respectively, but with high enantioselectivity (ee 100 %). Aubergine (Solanum melongena), cucumber (Cucumis sativus), white and red onion (Allium cepa), garlic (Allium sativum) and radish (Raphanus sativus) did not reduce the substrate even after 5 days of incubation. Hydrolysis of 1-acetoxy-2-methylcyclohexene with cucumber, mamey sapote (Pouteria sapota, fruit), banana passion fruit (Passiflora tarminiana, fruit), red onion, garlic and radish gives the S-ketone (ee 33-44 %). The further incubation of 2-methylcyclohexanone with such plants as carrot, cherimoya (Annona cherimola), wild cucumber (Cyclanthera pedata), giant granadilla (Passiflora quadrangularis), oca (Oxalis tuberose) afforded the enantiomercally pure trans- and/or cis-alcohol, respectively.

Figure 2 Bruni et al. (2002) investigated the reduction of acetophenone and the hydrolysis of 1-acetoxy-2 methylcyclohexene with plants to the corresponding S-carbinol and S-ketone, Scheme 1. Results showed that carrot (Daucus carota) reduced the acetophenone to the pure (S)-1-phenylethanol after 3 days with ee of 100 %. Lower yields were achieved with fenne (Foeniculum vulgare) and marrow (Cucurbita pepo), 37 and 10 %, respectively, but with high enantioselectivity (ee 100 %). Aubergine (Solanum melongena), cucumber (Cucumis sativus), white and red onion (Allium cepa), garlic (Allium sativum) and radish (Raphanus sativus) did not reduce the substrate even after 5 days of incubation. Hydrolysis of 1-acetoxy-2-methylcyclohexene with cucumber, mamey sapote (Pouteria sapota, fruit), banana passion fruit (Passiflora tarminiana, fruit), red onion, garlic and radish gives the S-ketone (ee 33-44 %). The further incubation of 2-methylcyclohexanone with such plants as carrot, cherimoya (Annona cherimola), wild cucumber (Cyclanthera pedata), giant granadilla (Passiflora quadrangularis), oca (Oxalis tuberose) afforded the enantiomercally pure trans- and/or cis-alcohol, respectively.

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Fig.1. Asymmetric reduction of ketones catalyzed by plants tissue (Yang et al., 2010) an enzyme reaction in a way that: oxidized substrate bind to is reduced, w enzyme, and 4) t for the process to begin 2009), Fig. 1. T biocatalytic pathways is chemistry of the implementation o help the industry such as, alco obtainable enantiomerical purity reaction types and s biotransformation depend in the substra oO meet t in bio herefore, function together to catalyze the 1) the coenzyme and an enzyme, 2) substrate hile the coenzyme is oxidized, 3) the coenzyme and reduced product detach he coenzyme is recycled and ready from the again (Matsuda et al., further exploration of a major part of the future. More vast assaying and f these biocatalytic met hods will he demand for substrates hols and amines, which are easily ransformations with Fruchey, 2011). The ereochemistry in the on the functional group es and the structural moieties in the vicinity of the functiona group (Ishihara et al., 2003). However, a common problem that occurs when using vegetables as biocatalysts is the effect of microbial contamination (Fruchey, 2011). Thus, microorganisms may be involved in_ the asymmetric reduction process when plants are used as an enzyme carrier (Matsuda et al., 2009). where L represents a large substituent and S a small substituent adjacent to the carbonyl group, Fig. 2 (Prelog, 1964). There are many reports describing synthesis of chira secondary alcohols using different parts of plant tissue (Baldassarre et al., 2000; Kumaraswamy and Ramesh, 2003; Comasseto et al. 2004; Maczka and Mironowicz, 2002). Since 2000 common carrot plan has been used repeatedly as an effective agent to perform the stereoselective reduction of many ketones while acetophenone derivates are probably the mos studied substrates used for enantioselective bioreduction to the corresponding alcohols (Rodrigues et al., 2004 and 2007). In general, the reductions of acetophenone derivatives into chiral alcohols follow Prelog’s rule, which predicts that hydrogen transfer to the prochiral ketone always occur from the Re-face
Fig.1. Asymmetric reduction of ketones catalyzed by plants tissue (Yang et al., 2010) an enzyme reaction in a way that: oxidized substrate bind to is reduced, w enzyme, and 4) t for the process to begin 2009), Fig. 1. T biocatalytic pathways is chemistry of the implementation o help the industry such as, alco obtainable enantiomerical purity reaction types and s biotransformation depend in the substra oO meet t in bio herefore, function together to catalyze the 1) the coenzyme and an enzyme, 2) substrate hile the coenzyme is oxidized, 3) the coenzyme and reduced product detach he coenzyme is recycled and ready from the again (Matsuda et al., further exploration of a major part of the future. More vast assaying and f these biocatalytic met hods will he demand for substrates hols and amines, which are easily ransformations with Fruchey, 2011). The ereochemistry in the on the functional group es and the structural moieties in the vicinity of the functiona group (Ishihara et al., 2003). However, a common problem that occurs when using vegetables as biocatalysts is the effect of microbial contamination (Fruchey, 2011). Thus, microorganisms may be involved in_ the asymmetric reduction process when plants are used as an enzyme carrier (Matsuda et al., 2009). where L represents a large substituent and S a small substituent adjacent to the carbonyl group, Fig. 2 (Prelog, 1964). There are many reports describing synthesis of chira secondary alcohols using different parts of plant tissue (Baldassarre et al., 2000; Kumaraswamy and Ramesh, 2003; Comasseto et al. 2004; Maczka and Mironowicz, 2002). Since 2000 common carrot plan has been used repeatedly as an effective agent to perform the stereoselective reduction of many ketones while acetophenone derivates are probably the mos studied substrates used for enantioselective bioreduction to the corresponding alcohols (Rodrigues et al., 2004 and 2007). In general, the reductions of acetophenone derivatives into chiral alcohols follow Prelog’s rule, which predicts that hydrogen transfer to the prochiral ketone always occur from the Re-face
Table 1. Asymmetric reduction of acetophenone by various plants tissue (Yand et al., 2008)
Table 1. Asymmetric reduction of acetophenone by various plants tissue (Yand et al., 2008)
gee ea ee ee TAS. hydroxycamphor with the highest stereose alcohols important Chiral heteroaryl applications as Vee I ae ectivity. numerous es in the o-r™ have intermediai synthesis of biological active molecules. There are many reports describing synthesis using obtained from microbial/dif tissues, however, limi incu yields and most of ation in commercial ap bation time, low substrate enantioselectivity. studied the chiral reduction o prochiral Table 2. present in Daucus substituted the corresponding sing good (76-99 %). The biored methyl ketones corresponding chiral a ketones using Daucus carota, Scheme 2, They demonstrated carota e chira yields (60-95 %) and uction (pyridyls cohols biocatalysts ferent parts of plan these processes have plication due to long loading, poor isolated Lakshmi et al. (2011 f substituted heteroary that dehydrogenases selectively reduced aromatic heterocyclic methyl ketones to secondary alcohols in high enantioselectivity of different heteroaryl and pyrrole) to showed exclusively S configuration thus following common Prelog’s rule, whereas furan and thio phene derivatives have shown R configuration according to anti Prelog’s rule. Scheme 2. Chiral reduction of substituted heteroaryl pro chiral ketones by Daucus Carota (Lakshmi et al., 2011)
gee ea ee ee TAS. hydroxycamphor with the highest stereose alcohols important Chiral heteroaryl applications as Vee I ae ectivity. numerous es in the o-r™ have intermediai synthesis of biological active molecules. There are many reports describing synthesis using obtained from microbial/dif tissues, however, limi incu yields and most of ation in commercial ap bation time, low substrate enantioselectivity. studied the chiral reduction o prochiral Table 2. present in Daucus substituted the corresponding sing good (76-99 %). The biored methyl ketones corresponding chiral a ketones using Daucus carota, Scheme 2, They demonstrated carota e chira yields (60-95 %) and uction (pyridyls cohols biocatalysts ferent parts of plan these processes have plication due to long loading, poor isolated Lakshmi et al. (2011 f substituted heteroary that dehydrogenases selectively reduced aromatic heterocyclic methyl ketones to secondary alcohols in high enantioselectivity of different heteroaryl and pyrrole) to showed exclusively S configuration thus following common Prelog’s rule, whereas furan and thio phene derivatives have shown R configuration according to anti Prelog’s rule. Scheme 2. Chiral reduction of substituted heteroaryl pro chiral ketones by Daucus Carota (Lakshmi et al., 2011)
Table 2. Asymmetric reduction of substituted heteroaryl ketones by Daucus carota (Lakshmi et al., 2011)
Table 2. Asymmetric reduction of substituted heteroaryl ketones by Daucus carota (Lakshmi et al., 2011)
Table 3. Enantioselective reduction of 2-chlorofluorenone using biocatalysts (Xie et al. 2009)
Table 3. Enantioselective reduction of 2-chlorofluorenone using biocatalysts (Xie et al. 2009)
Scheme 3. Enantioselective reduction of 2-chlorofluorenone using biocatalysts (Xie et al., 2009) (Zizyphus jujube), topinambur (Helianthus tuberosus) and grape (Vitis spp.) as biocatalysts for fluorenones enantioselective reductions. Among the tested plants, the grape exhibited the best results with ee 99 % and 97 % conversion. In addition, all other plant species were able to reduce 2-chloro-fluorenone except garlic which was inactive under the reaction conditions used. However, the ee values and conversion rates varied a lot, Scheme 3, Table 3. The absolute configuration of the reduced product was R, the biocatalytic reduction followed anti-Prelog’s rule.
Scheme 3. Enantioselective reduction of 2-chlorofluorenone using biocatalysts (Xie et al., 2009) (Zizyphus jujube), topinambur (Helianthus tuberosus) and grape (Vitis spp.) as biocatalysts for fluorenones enantioselective reductions. Among the tested plants, the grape exhibited the best results with ee 99 % and 97 % conversion. In addition, all other plant species were able to reduce 2-chloro-fluorenone except garlic which was inactive under the reaction conditions used. However, the ee values and conversion rates varied a lot, Scheme 3, Table 3. The absolute configuration of the reduced product was R, the biocatalytic reduction followed anti-Prelog’s rule.
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