This worked for me.
Copy all files from the Windows 8 DVD to a local folder eg. C:\Win8Media
oscdimg.exe -m -o -u2 -udfver102 -bootdata:2#p0,e,bE:\Win8Media\boot\etfsboot.com#pEF,e,bE:\Win8Media\efi\microsoft\boot\efisys.bin E:\Win8Media E:\win8pro-uefi.iso