Well, in the absence of any further details, you could try something like this:
RewriteRule (.*)/main/(.*) $1/$2
But this is a VERY broad rule - you'd probably want to tune it more tightly than that. Try turning the RewriteLogLevel to 9 and watching the rules as they get processed so you can get a better idea of what is being matched.
If you only need one file to be rewritten :
or else the TML answer is good :
It rewrites any URL with a /main (even in third, fourth, ... places) in it to prefix/suffix URL.
Well, in the absence of any further details, you could try something like this:
But this is a VERY broad rule - you'd probably want to tune it more tightly than that. Try turning the RewriteLogLevel to 9 and watching the rules as they get processed so you can get a better idea of what is being matched.