Need Another Mechanism

According to the hypothesis I posted a few days ago, exposing one of our Ugi products missing a methyl group on the furan to 50%TFA/CDCl3 should still cause the furfuryl group to cleave.

But looking at the monitoring H NMRs of EXP101 up to 30 hours there is not even a trace of a reaction, including cyclization to a diketopiperazine.

This is getting interesting. What will it do with a group other than methyl (like t-butyl) at the furfuryl 5 position?