There's not much hope for that, I fear.
You'd have to isolate ALL the shadow areas, then apply the Levels effect to even things out. That's tough enough, but wait! There's more! You would have shadow EDGES to deal with: they can introduce odd-looking lines in the shot where no lines should be. If they are all razor-sharp, that's one thing. I doubt they are.
Now you know why DP's carry frames with HUGE diffusion filters on them. I fear you may be learning the hard way.
What do you think of the look of this shot???
How can I fix my shot so it will look better???
My standard reply to both of those questions is What shot? Show me the shot and I'll have an optinion. What dave said is probably right, but there's a lot you can do if the footage lends itself to flattening. We just have to see at least one frame of the shot before we can give you any ideas.
Provide a frame from the shoot for reference and people might be able to advise rather than shooting blanks...
Not only, no, but, heck no. While you're digesting what others have said, research "day for night" post production processing techniques and see if there's a suggestion (in those thousands of hits you will get on Google) you like other than reshooting. You can also research "sun slik" or "overhead rag" to find out how professionals control sunlight on big shoots.