Problems forming the peptide bond

Question 1

Problems forming the peptide bond - Random Combinations

Answer 1

Can form:
H2N-A-A-CO2H
H2N-B-B-CO2H
H2N-B-A-CO2H
AND TRIPEPTIDES
- Solution to this is using a protecting group to stop reactions you don't want happening from happening

Question 2

Problems forming the peptide bond - Acid- base reactions and HO- being poor LG

Answer 2

• use dicyclohexylcarbodiimide (DCC)

Question 3

What does proton exchange give?

Answer 3

• neutral dipeptide and a good LG

Question 4

Using DCC you get X and you get rid of X

Answer 4

a good leaving group (OH) and you get rid of water

Question 5

What is solid phase peptide synthesis?

Answer 5

Peptide synthesis in the lab done in test tubes in the C to N direction (other way round to cell synthesis)

Question 6

What are the stages in solid phase synthesis?

Answer 6

• polysterene beads
• synthesis of CD then AB
• cleave polysterene to reveal CO2H group
• treat with CF3CO2H (trifluoracetic acid) which is a very strong acid

Question 7

Solid phase synthesis pros and cons

Answer 7

Pros - good as can purify your product easily as you’re going along
Cons - linear synthesis, 90% yield for each stage, yield decreases the longer the PPC becomes.