Biocatalyzed synthesis

Khymenets, O., Joglar, J., Clapes, P., Parella, T., Covas, M.-I. and de la Torre, R., Biocatalyzed synthesis and structural characterization of monoglucuronides of hydroxytyrosol, tyrosol, homo-vanillic alcohol, and 3-(4 -hydroxyphenyl)propanol. Adv. Synth. Catal., 2006, 348, 2155. 

Finally, a recent example on the biocatalyzed synthesis of new cytotoxic derivatives of the anthracycline doxurobicin (8) deserves to be mentioned. In the presence of Mucorjavanicus lipase or subtilisin Carlsberg ion-paired with Aerosol , the primary C-14 OH was chemoselectively acylated to give the corresponding derivatives, such as the valerate 8a [19]. However, optimization of this enzymatic synthesis did not provide a synthetic approach suitable for the preparative synthesis of gram quantities of Valrubicin (N-trifluoroacetyl doxurobicin-14-valerate, 8b)... 

The application of the non-urethane PhAc blocking group results in ca. 6% racemization during the construction of the phenylacetamido-protected dipeptides by chemical activation of the phenylacetamido amino acids. This disadvantage can be overcome by forming the peptide bonds enzymatically, e.g. with trypsin [26,27], chymotrypsin [26,28], or carboxypeptidase Y [26,29]. An interesting example is the biocatalyzed synthesis of leucine-enkephalin tert-butyl ester [25e], in which phenylacetamides are introduced and cleaved by means of penicillin G acylase, and the elongation of the peptide chain is carried out with papain or a-chymotrypsin. 

Mutation of the Ar l also yielded a thioligase for the preparation of thiofuranosides. ° Within this study, thioimidate such as 54 was used as a new donor in the biocatalyzed synthesis of carbohydrates and we have also shown that the coupling reaction proceeded with remote activation (Fig. 10). 

SCHEME 1.1 Biocatalyzed synthesis of isoindolo[2,l-a]quinazolines carried out by Raval and coworkers using baker s yeast as the catalyst [45a]. 

Biocatalyzed Synthesis of Probe 1 The fluorogenic compound 1 was prepared by a chemoenzymatic route starting from commercially available umbeUiferone [24a] (Scheme 15.7). 

Biocatalyzed Synthesis of Probe 7 Following a chemoenzymatic strategy analogous to that previously successful for fluorogenic probe 1, the chiral sugar moiety of compound 7 was established by highly stereoselective C-C bond formation catalyzed by RAMA in the presence of DHAP as donor substrate and the aldehyde precursor 13 as acceptor (Scheme 15.12) [25aj. 

However, when biocatalysts showing a sufficient cofactor specificity are not naturally available, possible undesired interferences between the cofactor regeneration systems can be circumvented by different approaches still maintaining the one-pot fashion of the multienzymatic process. For example, in the biocatalyzed synthesis of 12-ketoursodeoxycholic acid, the performances of the investigated cascade system, in which five enzymes were involved in concurrent oxidation and reduction reactions at different sites of the starting substrate cholic acid, were significantly improved by simple compartmentalization of the oxidative and reductive enzymes in two membrane reactors (Scheme 11.4b) [11]. 

L-tyrosine to phenol, pyruvate, and ammonium as well as the reverse reaction (Scheme 28.37). Therefore, it is of great interest because the biocatalyzed synthesis of L-tyrosine by TPL represents a single-step, straightforward, three-component reaction leading to the formation of selective C—C and C—N bonds. It can replace a four-step chemoenzymatic pathway using a kinetic resolution by lipase to obtain the optically enriched product. Nevertheless, the main disadvantage of TPL is its very narrow substrate spectrum. Seisser et al. developed several site-directed mutants to enlarge it (Scheme 28.37). 

A novel and more general method to enable biocatalyzed conversion and synthesis of hydrophobic compounds involves the use of gel-stabilized aqueous-organic two-phase systems [8], Features, advantages, disadvantages, and perspectives of this method in asymmetric synthesis will be discussed in this chapter, illustrated for the stereoselective benzoin condensation and the reduction of ketones catalyzed by thiamine pyrophosphate (TPP)-dependent lyases and NAD(P)H-dependent alcohol dehydrogenases, respectively. 

Biocatalyzed asymmetric conversion and synthesis of compounds with a low solubility or stability in aqueous solutions can be performed straightforwardly by... 

Besides using microreactor devices for efficient screening of biocatalysts, these can also be applied for enzymatic synthesis. Biocatalyzed reactions have recently received much attention because of the efficiency and selectivity that enzymes have to offer, combined with their ability to act under mild conditions [422,423]. Microreactors offer in this respect the advantage that enzymes can be more optimally used as a result ofthe higher mass-transfer properties of microchannels and the high surface-... 

Acrylamide with a demand of 200,000 tons year" is one of the most important commodities in the world. It is used for the preparation of coagulators, soil conditioners, stock additives for paper treatment, and in leather and textile industry as a component of synthetic fibers. Conventional chemical synthesis involving hydration of acrylonitrile with the use of copper salts as a catalyst has some disadvantages rate of acrylic acid formation higher than acrylamide, by-products formation and polymerization, and high-energy inputs. To overcome these limits since 1985, the Japanese company Nitto Chemical Industry developed a biocatalyzed process to synthesize... 

Biocatalyzed in water synthesis of chiral building blocks for the preparation of anti-cancer drugs A green approach 13COC1132. 

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