Amino Acids

Strecker synthesis

example

mechanism

amidomalonate synthesis

example

mechanism

reductive amination of a-keto acids

example

mechanism

Proteins

Protection-Deprotection Schemes

Example: Make the dipeptide Ala-Leu

Problem with linking two amino acids together:

To fix:

N-protect alanine

O-protect leucine

Now, react together

Deprotect

Merrifield Solid-Phase Technique

STEP 1: React a BOC-protected amino acid with the bromomethylated polystyrene.

STEP 2: Wash off excess reagent, and deprotect with trifluoroacetic acid.

STEP 3: React a second BOC-protected amino acid with the polymer-bound amino acid.

The cycle of deprotection, coupling, and washing is repeated as many times as desired to add amino acid units to the growing chain.

STEP 4: After the desired peptide has been made, treatment woth anhydrous HF removes the final BOC group and cleaves the ester bond to the polymer, yielding the free peptide.

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