[chykmandar]

Why required only 5-10% TFA to cleave peptide from 2-Chlorotrityl Chloride Resin and >95% TFA required to cleave peptide from Wang Resin?

Why 2-chlorotrityl is more acid labile than Wang linker?

What are cleavage mechanisms for both Resin?

Suggest website for having explanation of mechanism.

[orgopete]

Basically, the questioner gives the answer to the question. Let me restate it, "Which is more stable or can be formed most readily, a 2-chlorotrityl cation or a p-alkoxybenzyl cation?" The answer is the trityl.

Let me do a little speculating. Both linkers are capable of electronic tuning with substituents. Presumably a benzyl cation is too difficult to form so an oxygen was added to increase the ease of carbocation formation. Similarly, a trityl may have been to easy to form and is too labile. Adding an ortho chloro group will decrease its lability. (I didn't try to look up rates.)

Protonation of one of the basic electron pairs will enable C-O bond cleavage to form the carbocation. With the Wang resin, I might also expect protonation of the phenyl oxygen and thus compete with the cleavage step.