VPN nat one side to public facing network other side

Hiya
We are wanting to set up a vpn connection between 2 sites.

SITE 1:This site has an internal subet and is using NAT .
SITE 2 :This site just has public IP addresses(public facing) and there is no NAT.

Can we create a VPN between the 2 sites is it possible. Servers on site 2 need to see the servers on the private lan on site 1 as been local.

The servers in site 2 are Exchange servers and we want to put the file witness on private LAN at site 1 .

We could do with a VPN of some sort but dont know if it can be done.

Whats the best thing to do?

If any one has some code or a link that would be great.

Mike