Not really. You could reduce by one line by using
a = num2cell(arrayfun(fun, [s.f1], [s.f2]));
for whatever that is worth.
You could go through struct2cell() and create a new cell with the result, but it is not going to be any simpler than what you already have.
You could do it in fewer lines using especially obscure syntax. I am the only person whom I have seen use that syntax in about a decade -- I posted an example a few months ago just to prove that it could be done -- and that it was not worth doing. It would not be any simpler: it would leave even fairly advanced MATLAB users scratching their heads and wondering, "Can you do that???"