Methyl glutamate

The residue was diluted in water (5 mL) and, if necessary, the pH adjusted to 7.0 with 1 M KOH before adsorption of the product on a column of Dowex 1X8 resin (200-400 mesh, AcO form, 2 cm x 10 cm). The column was washed with water (50 mL) and then eluted with AcOH aqueous solutions (50 mL of 0.1 m, 50 mL of 0.2 m and 50 mL of 0.5 M AcOH). The ninhydrin-positive fractions were combined and dried under reduced pressure to afford (25,4/ )-4-methyl glutamic acid 2 isolated as a white solid (192 mg, 41 %) and with a high purity (>98 %). 

Flory, in 1956, predicted that solutions of rodlike polymers could also exhibit LC behavior. The initial synthetic polymers found to exhibit LC behavior were concentrated solutions of poly(gamma-benzyl glutamate) and poly(gamma-methyl glutamate). These polymers exist in a helical form that can be oriented in one direction into ordered groupings, giving materials with anisotropic properties. 

Fig. 6. Effect of modifying temperature on EDA with the following modifying reagent and conditions ( ) (+)-erythro-2-methyltartaric acid, pH 5.0 5.2, 0°C (O) (S.S)-tartaric acid, pH 5.0-5.2, 0°C (A) ( + )-2-methyl glutamic acid, pH 5.0, 0°C (O) (S)-valine, isoelectric point, 0 C ( ) (S)-glutamic acid, pH 5.2, 0 C. Reaction conditions MAA (neat), 60"C, 80 100 kg/cm2.

Figure 19-5 Schematic representation of an important chemotactic system of E. coli, S. typhimurium, and other bacteria. The transmembrane receptor activates the autokinase CheA, which transfers its phospho group to proteins CheY and CheB to form CheY-P and CheB-P. CheY-P regulates the direction of rotation of the flagella, which are distributed over the bacterial surface. CheR is a methyltransferase which methylates glutamate carboxyl groups in the receptor and modulates the CheA activity. CheZ is a phosphatase and CheB-P a methylesterase.

Glutaminase also catalyzes acyl transfer from glutamic acid to methanol by the reverse of the reaction of methyl glutamate hydrolysis (7) ... 

Rates of hydrolysis of several substrates in water and in D20 have been compared (9). Average values of Vh2o/Vd2o were, for glutamine, 1.16 for methyl glutamate, 1.38 for glutamyl methylamide, 1.10 and for glutamic acid, 1.50. 

Taddol has been widely used as a chiral auxiliary or chiral ligand in asymmetric catalysis [17], and in 1997 Belokon first showed that it could also function as an effective solid-liquid phase-transfer catalyst [18]. The initial reaction studied by Belokon was the asymmetric Michael addition of nickel complex 11a to methyl methacrylate to give y-methyl glutamate precursors 12 and 13 (Scheme 8.7). It was found that only the disodium salt of Taddol 14 acted as a catalyst, and both the enantio- and diastereos-electivity were modest [20% ee and 65% diastereomeric excess (de) in favor of 12 when 10 mol % of Taddol was used]. The enantioselectivity could be increased (to 28%) by using a stoichiometric amount of Taddol, but the diastereoselectivity decreased (to 40%) under these conditions due to deprotonation of the remaining acidic proton in products 12 and 13. Nevertheless, diastereomers 12 and 13 could be separated and the ee-value of complex 12 increased to >85% by recrystallization, thus providing enantiomerically enriched (2S, 4i )-y-methyl glutamic add 15. 

Scheme 8.7 Taddol-catalyzed asymmetric synthesis of y-methyl glutamic acid 15.

Glu 6, a major constituent of dissolved free amino acids (DFAA) in marine sediments [71], has been detected in red algae (Rhodophyta) [72] and as a potential osmolyte in several marine bacteria, for example obligatory aerobic heterotrophs [70] and methanogenic archaebacteria [8], N-methyl-/ -glutamate has been reported solely as a natural product from the cyanobacterium Prochloron didemni [96]. 

Suzuki F and Onozata K. Pervaporation of benzene-cyclohexane mixture by poly(7-methyl glutamate) membrane and synergetic effect of their mixture on diffusion rate. J Appl Polym Sci 1982 27 4229-4238. 

Kainate receptors are permeant to Na /K+ (and Ca in some heteromeric combinations) and are involved in fast excitatory synaptic transmission. They are activated by glutamate, and selectively by kainate, domoic acid and 4-methyl glutamic acid. 

Substances related to MSG and purine 5 -ribonucleotides include peptides, amino acids (e.g. cysteine, homocysteine, cysteine S-sulfonic acid, aspartic acid, a-amino adipic acid, a-methyl glutamic acid, tricholomic acid, ibotenic acid), pyrrolidone carboxylic acid, 3-methyl thiopropyl amine, and others [2, 10], They are of less commercial interest than MSG, IMP, and GMP. Chemical structures of some of these substances are depicted in Fig. 3.53. Relative umami effects of some are shown in Tab. 3.49. Tricholomic acid and ibotenic acid have been found in the mushrooms Tricholoma muscarium and Amanita stroboliformis, respectively. 

Many intracellular proteins can be modified after their biosynthesis by the enzymatic addition of a methyl group from S-adenosylmethionine. These posttransla-tional reactions can permanently or temporarily modify the structure and function of the target proteins. Importantly, these modifications can expand the repertoire of the cellular chemistry performed by proteins. Unmodified proteins must function with only the 20 amino acid residues incorporated in ribosomal protein synthesis, while methylation reactions can create a variety of new types of residues for specialized cellular roles. At this point, we understand best the processes that reversibly form methyl esters at carboxylic acid residues. One such reaction in bacteria methylates glutamate residues on several membrane-bound chemorecep-tors whose signaling properties are modulated by the degree of modification at multiple methylation sites. Another methylation system in higher cells leads to C-terminal methyl ester formation on a variety of proteins such as the small and... 

Methylation. A group of enzymes, referred to as the protein methyltrans-ferases, use S-adenosylmethionine to methylate certain proteins. For example, one type of methyltransferase found in E. coli and related bacteria methylates glutamate residues in membrane-bound chemoreceptors. The methyltransferase and a methylesterase are components in a methylation/demethylation process, which plays a role in a signal transduction mechanism involved in chemotaxis. (Recall that the capacity of a living cell to respond to certain environmental cues by moving toward or away from specific molecules is referred to as chemotaxis.)... 

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