*headscratching.* They want to *emphasize* that back end? I don't suppose there's any more-flattering distant views?
Kind of a tall order, I think. I don't think the building was really designed to be viewed the way they seem to be asking. I would try getting distance: if you try wide-angle closer to that big white addition, it'll look like a featureless monstrosity.
With some range and a longer lens you could put all those features together and maybe de-emphasize all the asphalt of the parking lot.
Agreed that there's probably a use of fill needed in that entry, if they want it emphasized. First thought I had was a night shot on 'Bulb' with a manual flash: walk around and hit your areas with a pop or two, depending on emphasis and what ought to look good, (A Vivitar 285 is good for this, though it's a white building, so you'll have to be on your game)
Easier: Choose a lower-lighting condition. Dawn, sunset, whatever looks good. I bet there's an overhead light in that entryway. Replace it with like a floodlight bulb.
Also, walk around. Don't feel constrained by a notion of framing around that big addition, there. Sometimes less is more, and you only need to *imply* it's there. (obviously with emphasis, as your 'client' requested. ) It's not actually much to look at, though. You can get the idea without showing it all the way back to the back corner, so leave that option open. Walk around and do some studies.