Glutamate chirality

Another example is a chiral olefinic alcohol, which is disconnected at the double bond by a refro-Wittig transform. In the resulting 4-hydroxypentanal we recognize again glutamic acid, if methods are available to convert regio- and stereoselectively... 

Ammonia reacts with the ketone carbonyl group to give an mine (C=NH) which is then reduced to the amine function of the a ammo acid Both mine formation and reduc tion are enzyme catalyzed The reduced form of nicotinamide adenine diphosphonu cleotide (NADPH) is a coenzyme and acts as a reducing agent The step m which the mine is reduced is the one m which the chirality center is introduced and gives only L glutamic acid... 

Licjuid Crystals. Ferroelectric Hquid crystals have been appHed to LCD (Uquid crystal display) because of their quick response (239). Ferroelectric Hquid crystals have chiral components in their molecules, some of which are derived from amino acids (240). Concentrated solutions (10—30%) of a-helix poly(amino acid)s show a lyotropic cholesteric Hquid crystalline phase, and poly(glutamic acid ester) films display a thermotropic phase (241). Their practical appHcations have not been deterrnined. 

The a-carbon of glutamic acid is chiral. A convenient and effective means to determine the chemical purity of MSG is measurement of its specific rotation. The specific optical rotation of a solution of 10 g MSG in 100 mL of 2 A/HQ is +25.16. Besides L-glutamic acid [56-86-0] D-glutamic acid [6893-26-1] and the racemic mixture, DL-glutamic acid [617-65-2] are known. Unique taste modifying characteristics are possessed only by the L-form. 

For the separation of amino acids, the applicability of this principle has been explored. For the separation of racemic phenylalanine, an amphiphilic amino acid derivative, 1-5-cholesteryl glutamate (14) has been used as a chiral co-surfactant in micelles of the nonionic surfactant Serdox NNP 10. Copper(II) ions are added for the formation of ternary complexes between phenylalanine and the amino acid cosurfactant. The basis for the separation is the difference in stability between the ternary complexes formed with d- or 1-phenylalanine, respectively. The basic principle of this process is shown in Fig. 5-17 [72]. 

Ethyl (bornylideneamino)acetate (2) and the imines of (-)-(lf ,2, 5 )-2-hydroxy-3-pinanone and glycine, alanine and norvaline methyl esters were particularly successful as Michael donors. The chiral azaallyl anions, derived from these imines by deprotonation with lithium diisopropylamide in THF at — 80 C, add to various a,/i-unsaturated esters with modest to high diastereoselectivity (see Section 1.5.2.4.2.2.5.). Thus, starting with the imine 2, (R1 = CH,) and ethyl ( )-2-butcnoate, the a,/i-dialkylated glutamate derivative 3 is obtained as a single diastercomer in 90% yield91-92. 

Diastereoselective preparation of a-alkyl-a-amino acids is also possible using chiral Schiff base nickel(II) complexes of a-amino acids as Michael donors. The synthetic route to glutamic acid derivatives consists of the addition of the nickel(II) complex of the imine derived from (.S )-,V-[2-(phenylcarbonyl)phenyl]-l-benzyl-2-pyrrolidinecarboxamide and glycine to various activated olefins, i.e., 2-propenal, 3-phenyl-2-propenal and a,(f-unsaturated esters93- A... 

Figure 14 Chiral separation of dansyl amino acids by chiral polyacrylamide gel electrophoresis. Peak identification 1 = dansyl-L-glutamic acid, 2 = dansyl-D-glutamic acid, 3 = dansyl-L-serine, 4 = dansyl-D-serine, 5 = dansyl-L-leucine, 6 = dansyl-D-leu-cine. (From Guttman, A., Paulus, A., Cohen, A. S., Grinberg, N. and Karger, B. L., /. Chromatogr., 448, 41, 1988. With permission.)...

Surface faceting may be particularly significant in chiral heterogeneous catalysis, particularly in the N i/P-ketoester system. The adsorption of tartaric add and glutamic acid onto Ni is known to be corrosive and it is also established that modifiers are leached into solution during both the modification and the catalytic reaction [28]. The preferential formation of chiral step-kink arrangements by corrosive adsorption could lead to catalytically active and enantioselective sites at step-kinks with no requirement for the chiral modifier to be present on the surface. 

Rundlett, K.L., Armstrong, D.W. (1994). Evaluation of free D-glutamate in processed foods. Chirality 6, 227-282. 

Stereostructure-activity studies on agonists at the AMPA and kainate subtypes of ionotropic glutamate receptors. Chirality, 15, 167-179. 

Chiral dialkyl amphiphiles [61] and [62], prepared from alanine and glutamic acid (Kunitake et al., 1979b), also form bilayer structures when dispersed in water. Chiral bilayers should be interesting because they provide... 

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