Green Chemistry and Engineering by Marteel-Parrish Anne E.; Abraham Martin A.; & MARTIN A. ABRAHAM

Author:Marteel-Parrish, Anne E.; Abraham, Martin A.; & MARTIN A. ABRAHAM
Language: eng
Format: epub
Publisher: Wiley
Published: 2013-10-09T16:00:00+00:00

Aspartame was discovered by accident by Jim Schlatter, a chemist at G.D. Searle in 1965. Jim Schlatter was working on drugs for the treatment of gastric ulcers when he spilled some aspartyl-phenylalanine on his hand. He later licked his finger and noticed the sweet taste of the compound, which later became aspartame. Aspartame is the methyl ester of the dipeptide of the natural amino acids L-aspartic acid and L-phenylalanine. There are four possible diastereoisomers for aspartame but aspartame is the only one having sweetening properties. The taste of aspartame would not have been predictable based on its amino acid constituents.

Aspartame is made of two amino acids that are chiral. The chemical synthesis starts with a racemic mixture, which contains equal quantities of both isomers of the two amino acids. The L isomers of both phenylalanine and aspartic acid are the only desired ones. The other isomers must be removed, therefore becoming waste.

The first step in the synthesis of aspartame is the ester synthesis where L-phenylalanine reacts with methanol in the presence of hydrochloric acid. The product is the methyl ester of phenylalanine (Scheme 6.4a). The second step is the amide synthesis, which is the reaction of the methyl ester of phenylalanine with aspartic acid (Scheme 6.4b).

Scheme 6.4. (a) First step in the synthesis of aspartame and (b) second step in the synthesis of aspartame.

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