Installing WordPress with /wp path leads to redirect loop when index.html redirects to a shopping cart

So on my site, my shopping cart is located at

I use this .htaccess file

RewriteEngine On  Redirect /index.html 

So that anyone that lands on will be redirected to my shopping cart.

All good, but now if I try and install WordPress at then browsers get stuck in a redirect loop.

I am positive it is my badly crafted .htaccess file.

What can I do to fix this?