The herbicide glyphosate (Roundup®) kills plants by inhibiting an enzyme needed for synthesis of phenylalanine. Deprived of phenylalanine, the plant cannot make the proteins it needs, and it gradually weakens and dies. Although a small amount of glyphosate is deadly to a plant, its human toxicity is quite low. Suggest why this powerful herbicide has little effect on humans.

Show how you would synthesize any of the standard amino acids from each starting material. You may use any necessary reagents.

(a)

Show how the following amino acids might be formed in the laboratory by reductive amination of the appropriate α-ketoacid.

(a) alanine

Show how you would synthesize any of the standard amino acids from each starting material. You may use any necessary reagents.

(b)

Show how you would use bromination followed by amination to synthesize the following amino acids.

(b) leucine

Give equations for the formation and hydrogenolysis of N-benzyloxycarbonyl methionine.

Three peptides were obtained from a trypsin digestion of two different polypeptides. In each case, indicate the possible sequences from the given data and tell what further experiment should be carried out in order to determine the primary structure of the polypeptide.

a. polypeptide I:

1. Val-Gly-Asp-Lys

2. Leu-Glu-Pro-Ala-Arg

3. Ala-Leu-Gly-Asp

Show the peptides that would result from cleavage by the indicated reagent: 

a. Val-Arg-Gly-Met-Arg-Ala-Ser by carboxypeptidase A

b. Ser-Phe-Lys-Met-Pro-Ser-Ala-Asp by cyanogen bromide

c. Arg-Ser-Pro-Lys-Lys-Ser-Glu-Gly by trypsin

Show how valine can be prepared by

d. a N-phthalimidomalonic ester synthesis.