Take a look at this example. It shows doing the same optimization using lsqcurvefit and fminunc. Both simulannealbnd and fminunc use the same scalar objective function.
But if you will allow me to make a suggestion, you will probably be happier running MultiStart and lsqcurvefit for longer rather than using simulannealbnd. This is because the efficiency of simulannealbnd is very low. If you want, you can try running patternsearch from a large number of random start points. That might not be better than MultiStart and lsqcurvefit, but it would almost certainly beat simulannealbnd.
Alan Weiss
MATLAB mathematical toolbox documentation