Help me make this simple regex redirection please.

i want to redirect this:
http://www.url1.com/downloads/"http://www.url2.com/blah.jar"

to

http://www.url2.com/blah.jar

i tried with:
from url: http://www.url1.com/downloads/"([A-Za-z0-9]*)"
url destiny: $1

but had no luck, i don't know how to use regex properly.