Now King Felipe has come out to answer... He was not aware of anything until a London law firm (the Royal House does not say it but they are Corinna's lawyers) sent him a letter last year (they do not clarify with what intentions they did) where they said it but without no document proving it. King Felipe sent the letter to the authorities, and made a notarial act explaining his ignorance, and that neither he nor in the name of his daughter had accepted anything.
The press release from Casa Real says that when the British law firm informed him (without any evidence) of his supposed designation as beneficiary of the foundation he did three things: he sent a copy of the letter to the authorities, another to his father and informed the law firm that he had no knowledge, participation or responsibility in the foundation and that he was not going to appoint a legal representative to open a negotiation about this with Corinna's law firm.
To me, reading between the lines, this last sentence about the supposed negotiation Corinna's lawyers wanted sounds like blackmail. We won't leak details to the press if you help us (Corinna was under investigation for financial crimes).
In the end, Corinna started the leaks about JC, and when that got her nowhere, she played her last card trying to involve Felipe.