So you want:
RewriteEngine On
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteRule ^example$ /directory1/directory2/directory3/example.html [L]
If you want it to work for every file (replacing "example" with any file) then replace the RewriteRule
line with:
RewriteRule ^([^/]+)$ /directory1/directory2/directory3/$1.html [L]