Valine purification

Other 2,3-Diphosphoglycerate Pocket Cross-Linkers. The reactivity of the valine NAl(l)a and lysine EF6(82)p residues in the 2,3-DPG pocket shown by NFPLP and (bis-PL)P4 has stimulated the search for other reagents that react similarly but have potential for greater efficiency and ease of scaleup. The systematic study of four different dicarboxyhc acid derivatives, cross-linked in both oxygenated and deoxygenated conditions, has been reported (92). Each of these derivatives presents problems in purification, and proof of the sites of reaction is tedious. 

In examining the effect of solution composition on the purity of recovered L-Ile crystals some unusual observations have been noted. Figure 7 shows data similar to that presented in Figure 4 for L-Ile HCMl20 with one major difference L-Valine is relatively unimportant as an impurity in comparison to L-Leu. Even though there is greater scatter in the data than was observed in the acid-addition experiments, purification factors for the two impurities are less than one and nearly constant. 

SE Jensen, A Wong, MJ Rollins, DW Westlake. Purification and partial characterization of delta-(L-alpha-aminoadipyl)-L-cysteinyl-D-valine synthetase from Streptomyces clavuligerus. J Bacteriol 172 7269-7271, 1990. 

A Vancura, I Vancurova, J Vole, SM Fussey, M Flieger, J Neuzil, J Marsalek, V Behai. Valine dehydrogenase from Streptomycesfradiae. purification and properties. J Gen Microbiol 138 3213-3219, 1988. 

These observations imply that the Cu oxidant is little sensitive to the steric surroundings of the hydroxyl function. The scope of the reaction can be further extended to protected primary p-amino alcohols with equal efficiency. The oxidation of dibenzyl valinol (Entry 6), which contains a tertiary nitrogen atom, proceeds in excellent yield. Moreover, the involvement of a neutral medium is ideally demonstrated by the lack of racemization of both dibenzyl valinal and Boc-prolinal (Entries 6 and 7). Purification of this latter product, which was prepared on a gramm-scale, necessitated only a simple filtration (32). 

The organic phase is dried over sodium sulfate, and solvent is removed by rotary evaporation to leave 1132 mg (97%) of the crude pale-yellow tripeptide. For further purification the crude product is dissolved in ethyl acetate, treated with some activated carbon and filtered through Celite. Removal of the solvent and crystallization from ethyl acetate/ether/petroleum ether (ca. 2 1 1) yields 993 mg (85%) of colorless crystals of benzyloxy-carbonyl-L-aspartyl-(tert-butyl ester)-L-phenylalanyl-L-valine methyl ester mp 119-120°C (Note 5). 

Additions of valine, leucine, and isoleucine were found to relieve the growth inhibitory effects of TP on Bacillus cell cultures, soybean cell cultures, and Arabidopsis seedlings. ALS isolated from a number of sources was found to be sensitive to TP at nM levels. The barley enzyme has been amenable to purification. A purification procedure that gives >60 % recovery and 235-fold purification is described. 

The present procedure for the preparation of oxazolidinone 3 is a variation of the procedures described by Luche" and Davies. Yields have been substantially enhanced by improving the purification procedures. The preparation of 3 starting from valine methyl or ethyl ester hydrochloride has been described by several authors. > > > These procedures suffer from moderate yields for the Grignard addition step and some of them use hazardous reagents like phosgene. 

The iron was removed from the peptide by oxidation with performic acid and the resulting peptide after purification over a column of talcum powder was treated with NBS (Saltiel and Patchornik, 1961) at pH 2, for 20 min at room temperature. Excess NBS was destroyed by the addition of formic acid. The reaction mixture was dinitrophenylated at pH 8.5, and the DNP-peptides were hydrolyzed with HCl. After resolution by two-dimensional paper chromatography DNP-Val, DNP-Thr, and DNP-Thr-Val-Glu were identified. The latter was formed due to incomplete hydrolysis of the peptide bond next to valine. The extent of cleavage of the His-Thr bond was found to be 20 %. 

The main Evans oxazolidinones are 87/88, derived from phenylalanine, and 89/90, derived from valine. All are available at a price - higher naturally for the unnatural R-isomers. Generally 87/88 are preferred as most of their derivatives are crystalline so that purification of diastereoisomers is easier.11... 

In a similar fashion, resin-bound imines 109 were employed to prepare a library of structurally diverse P-lactams by [2+2] cycloaddition reactions with different ketenes. Thus, as shown in Scheme 4.1.22, amino acids tethered to the acid labile Sasrin resin (103) were condensed quantitatively to imines 109 by using a large excess of alkyl, aryl, or a,P-unsaturated aldehydes in a mixture of trimethylorthoformate and dichloromethane. Optimisation studies of the [2+2] cycloaddition step, showed that conversion to P-lactams 110 could only take place by slow addition of acid chlorides to a suspension of the imine resin at 0°C in the presence of triethylamine. By using a large excess of ketene at high concentration, the cycloaddition of imines derived from even sterically hindered amino acids [e.g. valine) could be carried out with full conversion. After mild TFA cleavage from the resin and preparative HPLC purification, the p-lactams 111, 112 were isolated in yields of 55-97%. 

Dufour, E., Obled, A., Valin, C., Bechet, D., Ribadeaudumas, B. Huet, J.C. (1987). Purification and amino-acid sequence of chicken liver cathepsin-L. Biochemistry, 26, 5689-95. 

Ikeda, Y. Tanaka, K. (1983) J. Biol. Chem. 258, 9477-9487. Purification and characterization of 2-methyl-branched chain acylcoenzyme A dehydrogenase, an enzyme involved in the isoleucine and valine metabolism, from rat liver mitochondria. 

Since there are at least 20 different transfer RNA s (one per amino acid), it was necessary to develop reliable methods of purification of a given transfer RNA before any attempt was made to study the base sequence. Transfer RNA was extracted with phenol and submitted to countercurrent distribution in a medium containing formamide, isopropyl alcohol, and a phosphate buffer. By this procedure, different types of transfer RNA (alanine, valine, histidine, and tyrosine) were separated from the bulk of the transfer RNA. 

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