Help with mex setup Fortran Matlab 2013b on OS X 10.8

I am trying to compile the yprime.F example, but I get the following error:

Undefined symbols for architecture x86_64: "_mexfunction_", referenced from: -exported_symbol[s_list] command line option ld: symbol(s) not found for architecture x86_64 clang: error: linker command failed with exit code 1 (use -v to see invocation)

    mex: link of ' "yprime.mexmaci64"' failed.

Here is the relevant part of my mexopts.sh file:

             FC='/usr/local/bin/gfortran'
                FFLAGS='-fexceptions -m64 -fbackslash'
                FC_LIBDIR=`$FC -print-file-name=libgfortran.dylib 2>&1 | sed -n '1s/\/*libgfortran\.dylib//p'`
                FC_LIBDIR2=`$FC -print-file-name=libgfortranbegin.a 2>&1 | sed -n '1s/\/*libgfortranbegin\.a//p'`
                FLIBS="$MLIBS -L$FC_LIBDIR -lgfortran -L$FC_LIBDIR2 -lgfortranbegin"
                FOPTIMFLAGS='-O'
                FDEBUGFLAGS='-g'

Could some one please point to instructions on how to setup the gfortran mex compilation capabilities??? Compiling prime.c is not a problem at all, but I am not a C programmer. Thanks!!!!