The 23-year-old is a reported target of the north London outfit, but De Boer has said that it would take a "super transfer fee" to prise him away from the Amsterdam ArenA.
Answering to the rumours linking Alderweireld with a move to White Hart Lane, Sky Sports News quotes De Boer as saying: "That's maybe something for next year. I think he'll end this season at Ajax.
"We're very happy with him and don't want to let him go in the winter unless it's a super transfer fee, but I don't think that will happen."
Alderweireld has won 19 caps for his country.