I have Nginx configured as reverse proxy

server {
listen 80;
server_name www.pluto.com;
location / {
proxy_set_header X-Forwarded-Host $host;
proxy_set_header X-Forwarded-Server $host;
proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
proxy_pass http://127.0.0.1:8080;
}
}
I need that the URL request from any combination of FOLDER1 (case insensitive) is rewrite from URL

http://www.pippo.com/FOLDER1/etc..etc..etc..
to (always lowercase folder1)

http://12.0.0.1/folder1/etc..etc..etc...
where etc..etc..etc. = anything that I need to keep

How can I do?