Reduction using baker’s yeast

The Shimizu group investigated the potential of another structural type of sulfide organocatalyst, 5- and 6-membered cyclic sulfides [211]. These sulfides were prepared by biocatalytic reduction using baker s yeast. In particular the 5-... 

Kinetic resolution of racemic dienal iron tricarbonyl complexes by reduction using baker s yeast has been developed. Porcine pancreatic lipase-catalyzed transesterification of hydroxymethyl-substituted complexes have also been used to kinetically resolve diene complexes (Scheme 127). 

Valerolactones. - Enantioselective reduction using Baker s yeast, a method most often associated with chiral 3-hydroxy-ester preparation, has also been applied to generation of the... 

Chiral (l-hydroxy esters are versatile synthons in organic synthesis, specifically in the preparation of natural products [62-64], The asymmetric reduction of carbonyl compounds using Baker s yeast has been demonstrated and reviewed... 

J-N Cui, R Teraoka, T Ema, T Sakai, M Utaka. Highly regio- and enantioselective reduction of l-chloro-2,4-alkanediones using baker s yeast effects of organic solvents as additives. Tetrahedron Lett 3021-3024, 1997. 

Synthesis of optically pure -y-lactones using asymmetric reduction by baker s yeast 91YGK647. 

Aminoisoxazoles were obtained from (Z)-3-alkyl-3-nitro-2-phenylpropenenitriles using baker s yeast <1996SL695>. Reductive cyclizations of 2-nitroacylarenes allowed the synthesis of anthranil derivatives. For example, a series of 5-substituted 2,1-benzisoxazoles where prepared by reduction with SnCl, and subsequent... 

Enzymatic reductions are commonly used in asymmetrical synthesis (see Chap. 10). One of the most common methods uses baker s yeast (S. cerevisiae). The complete... 

Pick a reduction by baker s yeast in a recent journal or in Organic Syntheses. Using this procedure try reducing a different compound by this method. 

Heterocyclic p-ketoesters have also been used as substrates for reduction, where the products often have use in the synthesis of pharmaceutical agents or natural products. Representative examples of heterocyclic p-hydroxyesters formed using Baker s yeast are given in Fig. 9-28165-71 . 

If the corresponding thio- and dithioesters are used, highly selective reductions by baker s yeast are achieved143. 

The saturation of a,/J-unsaturated ketones using baker s yeast as catalyzing cells was first described in 193544 Several examples are shown here. The a,/i-unsaturated ketones gave saturated ketones as a primary product. Substantial reduction of the ketone group was only observed after a prolonged reaction time. 

Another example using baker s yeast demonstrates the highly enantio- and diastcreoselective reduction of sulfur-functionalized 2-phcnylthio-2-cyclopentenone92. Optically active cyclopentane derivatives with multiple functionalization are useful starting materials for the synthesis of prostaglandins and related compounds. 

An enantioselective synthesis of (-)-nonactic acid and (+)-8-epi-nonactic acid using a microbial reduction step (baker s yeast) was reported <97SL159>. A highly enantiotopic-plane selective C-H oxidation of cyclic ethers (up to 82% ee) was achieved by using a (R.R)-(salen)manganese(Hl) complex as a catalyst <97SL836>. 

A mild and inexpensive way to reduce aldehydes or ketones uses fermenting Baker s yeast. This is a whole-cell system that contains oxidoreductase enzymes and cofactors that reduce the substrate. The ketonic carbonyl groups of (3-keto-esters and cyclic ketones are reduced with high selectivity using Baker s yeast. Typical in this regard is the reduction of ethyl acetoacetate, which gives ethyl 3-hydroxybutyrate as predominantly the (5)-stereoisomer (7.101). Similarly, the ketone 114 gave the optically active 3-hydroxyproline derivative 115 (7.102). 

Reduction of ketopantolactone using Baker s yeast gives an ee of approximately 72% but a chiral Rh catalyst has been shown to be superior to Baker s yeast in this process. 

In another report, the traditional oxazolidinone auxiliary was attached to the acyl chloride for the [2+2] cycloaddition with an imine. Thus, both Holton s and Palomo s groups reported the reaction of 7.1.12 and 7.1.13 to yield lactam 7.1.14 in a virtually complete stereoselective fashion. The asymmetry at the C-3 position of the lactam was destroyed by hydroxylation or chlorination at this position. Hydrolysis of the auxiliary was achieved with silica gel (Si02) or silver nitrate (AgNOs). Diastereoselective reduction of the key intermediate ketolactam 7.1.15 to give 7.1.16 was then effected with NaBH4 in MeOH at 0°C (241, 242). An alternate approach to chiral /3-lactam uses baker s yeast to reduce racemic ketolactam 7.1.15 (243). The desired isomer 7.1.16 was obtained in up to 80% ee at 50% conversion. 

A synthesis of derivatives of three of the four possible 2,3-di-deoxy-2-C-methyl-D-hexoses has been reported using Baker s yeast to achieve the stereospecific reduction of the racemic acetoxy ketone (41), the unreduced enantiomer being separately reduced stereo-specifically after C-5 epiraerization (Scheme 11). ... 

For example, consider one of the simplest reduction processes, namely the reduction of a ketone to a secondary alcohol. Of course, this can be accomplished chemically using sodium borohydride. The same transformation can be achieved using baker s yeast, and one advantage of using the biocatalyst often can be seen immediately (i.e. optically active forms of chiral alcohols can be obtained). The reason is simple The bio-reduction... 

Scheme 2.122 Reduction of aliphatic and aromatic ketones using baker s yeast...

Scheme 5.12 Entry 1) [27]. This process has a number of drawbacks, such as the requirement for high dilution conditions, the use of sucrose as reductant and difficult product isolation. Nevertheless, a wide range of applications using Baker s yeast (or other microorganisms) have since been developed [28]. For example, the COOR motif (in Scheme 5.12) can be replaced with other electron-withdrawing groups such as COSR [29], SOjR [30], SR [31] and CN [32]. In addition, p,8-diketo... 

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