Erwin Chargaff’s discovery that DNA contains equimolar amounts of guanine and cytosine and also equimolar amounts of adenine and thymine has come to be known as Chargaff’s rule:
G = C and A = T
(a) Does Chargaff’s rule imply that equal amounts of guanine and adenine are present in DNA? That is, does G = A?
(b) Does Chargaff’s rule imply that the sum of the purine residues equals the sum of the pyrimidine residues? That is, does A + G = C + T?
(c) Does Chargaff’s rule apply only to double-stranded DNA, or would it also apply to each individual strand if the double helical strand were separated into its two complementary strands?

Provide a synthesis of the following amino acids using a combination of the HVZ and amination reactions.

b. Leu

Show how you would synthesize the following amino acids using the Strecker amino acid synthesis.

a. Ala

Show how you would use a Strecker synthesis to make

(c) aspartic acid.

Show how you would use the Strecker synthesis to make tryptophan. What stereochemistry would you expect in your synthetic product?

Show how you would use a Strecker synthesis to make phenylalanine.

Propose a mechanism for each step in the synthesis in part (a).

Propose a mechanism for each step in the synthesis in part (a).

Predict the products of the following reactions.

(g) 4-methylpentanoic acid + Br₂/PBr₃ →