[Jfalken]

So I am looking at this mitsunobu reaction, but the nitrogen changes place and I am to propose a mechanism for it.
My idea is that since the LG will be positively charged, the free electron pair on the nitrogen could attack the carbon, forming four bonds and becoming positively charged.
Then the OHPh (if deprotonated maybe) could attack the first carbon the nitrogen is attached to and thus resetting the amin to its original state.

So left to middle is straight forward but right to middle is a bit more complicated to understand.
See picture;
https://i.postimg.cc/FR9gN5QN/Mit.jpg

[rolnor]

I think you have neigbouring participation by the amino group. Considering this, can you explain why get the stereochemistry you see?