Methylglutamic acid derivatives

Other Oxazolidine as well as Thiazolidine Derivatives for Branching Amino Acids. The cyclic derivative of alanine and other amino acids employed most frequently for a-allq lation is not (1) but rather the benzaldehyde acetal (5), either with a benzoyl or with a Cbz group on nitrogen. These compounds were used for the preparation of 2-methyl-2-aminobutanoic acid, a-methylphenylalanine, a-methyllysine, 2-methylaspartic acid, and 2-methylglutamic acid. Bicyclic compounds containing oxazolidinone rings such as (6) (from alanine, leucine, and phenylalanine) and (7) (from azetidinecaiboxylic acid, proline, " hydroxyproline, and cysteine ) have also been applied to the synthesis of branched amino acids. 

The enolatc of (2S,4R)-I can also undergo Michael addition to f-butyl acrylate. The yield is low, but the adduct is obtained in 98% ee. This reaction provides a route to a derivative of 2-methylglutamic acid (equation I). 

Methylglutamic acid (9), (25, 45)-4-hydroxy-4-meth-ylglutamic acid (70) and 4-methyleneglutamic acid (26) apparently are derived from leucine (Fig. 13.14) (Rosenthal, 1982). All these compounds are found in honey locust, Gleditsia triacanthos (Fabaceae). 4-Methyleneglutamic acid (26) is also stored in the peanut, Arachis hypogaea (Fabaceae). 

Very mild treatment with alkali produced a ring-opened derivative, thus showing the presence of a lactone ring and allowing the release of P-methylglutamic acid by further treatment with carboxypeptidase. 

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