Amino acid amidomalonate synthesis

Amidomalonate synthesis (Section 26.3) A method for preparing a-amino acids by alkylation of diethyl amidomalonate with an alkyl halide. 

In the amidomalonate synthesis, shown above, an alkyl halide RX is converted to RCH(NH3+)CC>2H. Choose an alkyl halide that completes the structure of the target amino acid. 

A more general method for preparation of a-amino acids is the amidomalonate synthesis, a straightforward extension of the malonic ester synthesis (Section 22.7). The reaction begins with conversion of diethyl acetamidomalonate into an eno-late ion by treatment with base, followed by 5 2 alkylation with a primary alkyl halide. Hydrolysis of both the amide protecting group and the esters occurs when the alkylated product is warmed with aqueous acid, and decarboxylation then takes place to yield an a-amino acid. For example, aspartic acid can be prepared from ethyl bromoacetate, BrCH2C02Et ... 

A clever adaptation of this process, called the amidomalonate synthesis, employs diethyl acet-amidomalonate as the starting material, enabhng the preparation of racemic Ct-amino acids. 

PRACTICE the skill 25.14 Identify the reagents necessary to make each of the following amino acids via the amidomalonate synthesis. 

An amidomalonate synthesis was perfomned using each of the following alkyl halides. In each case, draw and name the amino acid that is produced. 

Both leucine and isoleucine can be prepared via the amidomalonate synthesis, although one of these amino acids can be produced in higher yields. Identify the higher yield process and explain your choice. 

Racemic mixtures of amino acids can be prepared in the laboratory via a-haloacids, via the amidomalonate nthesis, or via the Strecker synthesis. Optically active amino acids are obtained either via resolution of a racemic mixture or via enantioselective synthesis. 

The amidomalonate synthesis can be used to prepare amino acids from alkyl halides. When the amidomalonate synthesis is used to make glycine, no alkyl halide is required. Explain. 

Draw the alkyl halide that would be necessary to make the amino acid tyrosine using an amidomalonate synthesis. This alkyl halide is highly susceptible to polymerization. Draw the stmcture of the expected polymeric material. 

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