I've got a project in wordpress and seeking to create a rewrite rule. What I am attempting to do is - when the url is -

http://www.example.com/drupal/drupal-cms.html

, it will seem like,

http://www.example.com/blog/drupal/drupal-cms.html

I've written the rule as

RewriteRule  /(drupal)/([A-Za-z\-]+)(\.html) /blog/$1/$2$3

however with this it requires enough time to load the page and lastly, I receive 500 internal error.

How do i accomplish this ?