29. Amino Acids

Provide the Fischer Projection representation of D-Aspartic Acid. Indicate if the chiral center is R or S.

Convert the following Fischer Projection of L-Proline into a bondline structure.

Esterase is an enzyme that catalyzes the hydrolysis of esters. It hydrolyzes esters of l-amino acids more rapidly than esters of d-amino acids. How can this enzyme be used to separate a racemic mixture of amino acids?

Draw the structure of the phenylthiohydantoin derivatives of

(c) lysine.

Sometimes chemists need the unnatural d enantiomer of an amino acid, often as part of a drug or an insecticide. Most L-amino acids are isolated from proteins, but the D-amino acids are rarely found in natural proteins.

D-amino acids can be synthesized from the corresponding L-amino acids. The following synthetic scheme is one of the possible methods.

<IMAGE>

(a) Draw the structures of intermediates 1 and 2 in this scheme.

(b) How do we know that the product is entirely the unnatural d configuration?

Use Figure 23-3 <IMAGE> (the D family of aldoses) to name the following aldoses.

(d) the enantiomer of D-galactose

(e) the C5 epimer of D-glucose

Suggest how you would separate the free l-amino acid from its acylated D enantiomer in Figure 24-5.