Biotransformations

Abstract

CAL-B was also used in the separation of enantiomers of a precursor to peclitrexol, a glycinamide ribonucleotide formyltransferase inhibitor (Scheme 3). 3 The study was notable in using remote oxalamic ester derivatives to increase differential enantiomer recognition by the enzyme, resulting in E values of 45-49 for hydrolysis of the terminal ethyl ester of structure 11, leading to the desired (S)acid 12 with high optical purity.Novel types of substrate for lipase-catalysed reactions have also emerged. CAL-B was also used in conjunction with the complementary properties of lipase A from Candida antarctica (CAL-A) to synthesise a series of b-peptides. 4 In this study, CAL-B was used to activate a range of N-acetylated b-amino esters by interesterification using 2,2,2-trifluoroethylbutanoate as the acyl donor in dry diethyl Scheme 2 Scheme 3 Scheme 1

Studying non-covalent enzyme carbohydrate interactions by STD NMR

“…Protons of the product xylitol (5), in particular P-H2 and P-H1a, show pronounced STD effects from the early beginning of the measurement (indicated in gray and by dashed lines). Such high STD effects are caused by newly formed xylitol (5), which is released from the enzyme for the first time. Different increases of P-H2 and P-H1a STD effects appearing during progress of the reaction are likely caused by additional STD effects of xylitol (5) forming ternary CtXR-NADH-xylitol and CtXR-NAD + -xylitol complexes.…”

“…Figure 3. STD NMR spectra recorded during CtXR (10 lM) catalyzed and NADH (10 mM) consuming reduction of xylose (10 mM, 4) to xylitol (5). After a 1 H NMR spectrum recorded at the start (a) four STD NMR spectra were measured sequentially, each over 15 min (b-e) prior to measurement of a final 1 H NMR spectrum (f).…”

“…[1][2][3][4][5] They find applications in research and development 1,2,6-8 and are widely used in industrial processes. 9,10 Glycosidases and glycosyltransferases find use in the synthesis of glycosides and oligosaccharides, whereas oxidoreductases, lyases, and ligases are basically applied to modify monosaccharides.…”

Continuous Biocatalytic Processes

“…Biocatalytic processes continue to remain an area of intensive research, with a desire to develop alternative routes to the organic synthesis of fine chemicals. For example, the annual reports for 2006 and 2007 on biotransformations related to synthetic organic chemistry cite 98 and 87 references, respectively. , Continuous processes have several advantages over batch processes, including very low down-times for the reactors, higher space-time yields, optimized energy consumption, reactions under steady-state conditions, and many more. On the other hand, continuous processes necessitate the use of more expensive equipment, the use of catalysts with a long life, automation to a large degree in instrumentation and process control, and the availability of downstream processing technologies to separate the product from the unreacted reactants, intermediates, and byproducts.…”