You will have to move your file "synergyc" to a place where it can be executed:
Run in a terminal
you should get somthing like>
Code:
/usr/local/sbin:/usr/local/bin:/sbin:/usr/sbin:/bin:/usr/bin:
In your case I think /usr/bin/ is not a bad idea.
Then put the following line into your /etc/rc.d/rc.local
Code:
/usr/bin/synergyc -f --daemon 161.50.18.207
This should do the trick.