Chemistry: SPPS/Protecting Groups(Boc/Fmoc)/Peptide Question

[grint]

Question with part of answer:
http://i.imgur.com/5Nki1SM.png

More answer with questions:
C-terminus should a carboxylic acid for both as the ester and amide will be acid hydrolyzed.
The ester linkage should be more susceptible to acid because it is more reactive than the amide. This is because the oxygen is a worse electron donating group than the nitrogen therefore it is stabilized less by resonance. However, do I need to take into account the phenyl groups? They are electron donating and may make the ester stronger.

Either neither or both are employed with Boc chemistry. Neither because Boc is removed by strong acids and will thus be removed when the bonds are ester/amide bonds are hydrolyzed or both because Boc uses strong acid and the acid hydrolyzation doesn't need a strong acid?

Either neither or both are employed with Fmoc chemistry for the same reasons. Fmoc will be removed when the amide/ester bonds are base hydrolyzed or it won't be because it needs strong bases like piperidine.

Thanks for any help

 

[nate808]

!

Hello,

Thank you for your questions regarding the susceptibility of ester and amide bonds to acid hydrolysis in the context of Boc and Fmoc chemistry.

To answer your first question, the presence of phenyl groups in the molecule may indeed affect the strength of the ester bond. The electron-donating nature of the phenyl groups may stabilize the ester bond and make it less susceptible to acid hydrolysis. However, this effect may be minimal and may not significantly impact the overall reactivity of the ester bond.

In terms of Boc chemistry, it is possible that either neither or both ester and amide bonds are employed. This ultimately depends on the specific conditions and reactions being used in the synthesis. As you mentioned, Boc is removed by strong acids, so if the bonds are being hydrolyzed under acidic conditions, then Boc will also be removed. However, if the bonds are being hydrolyzed under milder conditions, then Boc may remain intact.

Similarly, in Fmoc chemistry, the use of strong bases like piperidine may also affect the stability of the amide bond. If the amide bond is being hydrolyzed under basic conditions, then Fmoc will also be removed. However, if milder conditions are used, then Fmoc may not be affected.

I hope this helps clarify any confusion and provides some insight into the potential effects of Boc and Fmoc chemistry on ester and amide bonds. Let me know if you have any further questions. Thank you.