As others have said- if you start with an older "10-speed" frame, originally set up for 27" wheels and with horizontal dropouts, you'll be able to create a single-speed bike with 700 x 35C tires pretty easily. I did this with an old Schwinn LeTour:
http://home.comcast.net/~jeff_wills/letour/index.htm (I know it's a 7-speed in the pictures- I've since reconfigured it as single speed) and it works great. If you shop around, you can even find good-quality NOS frames:
http://pedalr.com/items/707
Starting with an ATB frame is problematic. If the wheels fit, you'll have to do some adapting to get brakes to work. Even then, the cranks are going to be somewhat higher than the usual road bike. It's just going to end up weird.