L -Valine

The influence of a large number of oc-amino acids on the values of and k at have been determined. These a-amino acids included glycine, L-valine, L-leucine, L-phenylalanine, L-tyrosine, L-tryptophan, NOrmethyl-L-tryptophan (L-abrine), N-methyl-L-tyrosine, N,N-dimethyl-L-tyrosine and p -me thoxy-N-me thyl -L -phenyl al anine. 

Diamide Chiral Separations. The first chiral stationary phase for gas chromatography was reported by GH-Av and co-workers in 1966 (113) and was based on A/-trifluoroacetyl (A/-TFA) L-isoleucine lauryl ester coated on an inert packing material. It was used to resolve the tritiuoroacetylated derivatives of amino acids. Related chiral selectors used by other workers included -dodecanoyl-L-valine-/-butylamide and... 

A/- -toluene su1fony1)-T-phenylalanine (62), L-histidine methyl ester (63), A/-acetyl L-valine /-butyl amide (64), etc, are used as chiral addends. 

Many kinds of amino acids (eg, L-lysine, L-omithine, t-phenylalanine, L-threonine, L-tyrosine, L-valine) are accumulated by auxotrophic mutant strains (which are altered to require some growth factors such as vitamins and amino acids) (Table 6, Primary mutation) (22). In these mutants, the formation of regulatory effector(s) on the amino acid biosynthesis is genetically blocked and the concentration of the effector(s) is kept low enough to release the regulation and iaduce the overproduction of the corresponding amino acid and its accumulation outside the cells (22). 

V-Acetyl-L-valine amide [37933-88-3] M 158.2, m 275°. Recrystd from CH30H/Et20. 

Amino-4,6-dimethyl-3-oxo-3//-phenoxazine-l,9-dicarboxylic acid also named actinocin is the chromophor of the red antineoplastic chromopeptide aetinomyein D (formula A). Two cyclopenta-peptide lactone rings (amino acids L-threonine, D-valine, L-proline, sarcosine, and 7V-methyl-L-valine) are attached to the carboxy carbons of actinocin by two amide bonds involving the amino groups of threonine. 

A reversal of the 5 4H) 5 2H) equilibrium was established by demonstrating the presence of 4-isopropyl-2-trifluoromethyl-5(2fl )-oxazolone as an intermediate in the reaction of A-TFA-l-valine with the methyl ester of L-valine [Eq. (35)] using gas chromatography. The resulting product is a mixture of 74% l,l- and 26% d,l-A-TFA dipeptide methyl ester (see Section II, B, 4). 

Based on chiral functional monomers such as (15), MICSPs can be prepared using a racemic template. Thus, using racemic A-(3,5-dinitrobenzoyl)-a-methylbenzy-lamine (16) as template, a polymer capable of racemic resolution of the template was obtained [67]. Another chiral monomer based on L-valine (17), was used to prepare MIPS for the separation of dipeptide diastereomers [68]. In these cases the configu-... 

The first biosynthetic steps are two reactions that generate ACV from its constituent amino acids L-a-aminoadipic add, L-cysteine and L-valine. L-a-aminoadipic acid and L-cysteine are condensed by the enzyme AC synthetase and, in the next step, the resultant 8-(L-a-aminoadipyl)-L-cysteine is coupled with L-valine. In this step the configuration of L-valine is inverted to D-valine. 

Figure 6.9 Formation of isopenicillin N from its constituent amino acids. After condensation of L-a-aminoadipic acid with L-cysteine, L-valine is coupled. During this transformation, the configuration of the latter amino acid inverts to give D-valine.

Other amino adds produced by wild strains indude L-valine, DL-alanine and L-proline. 

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