MXF is just a container ... what codec do you need inside?
If the answer is "any codec" then you could go with the free solution offered by Sony's XDCAM Transfer app which allows you to export to DV, IMX or XDCAM HD codecs and simultaneously wrap them as MXF.
If the answer is more specific then you'll need a commercial solution such as MXF4Mac's D10 and GC Export options ( [
mxf4mac.com] )