Amino Acid Reactions

Question 1

What are two classic reactions used to synthesize amino acids?

Answer 1

Strecker synthesis and Gabriel Synthesis

Question 2

Strecker Synthesis

Answer 2

aldehyde + (KCN + NH4Cl) –> form an aminonitrile (CR + amine group + triple bond to N)

Next it is hydrolyzed in an acidic aqueous environment (add another H+ to it) and you get your amino acid

1. aldehyde + ammonia in presence of acid –> we get our imine (C double-bonded to N) and then water as the leaving group
2. Then, we take our imine, keep it in the acidic environment so it gets protonated, and then our KCN (CN- ion) acts as a nucleophile and attacks the alpha carbon, so then we are left with the aminonitrile
3. Then we hydrolyze everything and are left with the amino acid

Question 3

Gabriel synthesis

Answer 3

Gabriel malonic ester synthesis
1. start with a n-phthadimidomalonic ester (you need an ester and you need something with Nitrogen, but you need this to be v v controlled cuz this is SN2
2. Now we get to add our R groups - in the presence of a base (like NaOCH2CH3), and then our alkyl group with a good leaving group attached (like Br, Cl, any of the halides)
3. Now we’ve replaced the hydrogen that was on our alpha carbon with the R group we wanted to add (the alkylated step)
4. Next, put this molecule in an acidic environment (lots of H3O+), and we hydrolyze the ester groups and the phthalimide on the malonic ester, so we are now left with
Our alpha carbo, attached to an R group, attached to two carboxyl groups, attached to a protonated amine
5. Finally, we add heat to get the extra carboxyl group to leave