RewriteRule loop, content negotiation - .htaccess

Question

I have made the rounds through Stack Overflow, and I haven't found an answer to my question (or at least I didn't recognize it), so I decided to open my own question.
I am trying to set up a content negotiation system to serve HTML by default and when requested and RDF/XML when requested. The URI would be a non-information source. The user would go to the URI and it would redirect the user to the appropriate file based on the request. For example:
GET: http://example.com/ldExamples/catalog_001
Accept: application/rdf+xml
This should result in a redirect to http://example.com/ldExamples/catalog_001.rdf
I have tried a couple of approaches to this. All of the following code was adapted from W3C's Best Practice Recipes for Publishing RDF Vocabularies. Here's the first attempt:
# Turn off MultiViews
Options -MultiViews
# Directive to ensure *.rdf files served as appropriate content type,
# if not present in main apache config
AddType application/rdf+xml .rdf
# Rewrite engine setup
RewriteEngine On
RewriteBase /ldExamples
# Rewrite rule 2: to serve HTML content from class or prop URIs if requested
RewriteCond %{HTTP_ACCEPT} !application/rdf\+xml.* (text/html|application/xhtml\+xml)
RewriteCond %{HTTP_ACCEPT} text/html [OR]
RewriteCond %{HTTP_ACCEPT} application/xhtml\+xml [OR]
RewriteCond %{HTTP_USER_AGENT} ^Mozilla/.*
RewriteRule ^(.+)/$ $1.html [R=303]
# Rewrite rule 3: to serve RDF content is requested
RewriteCond %{HTTP_ACCEPT} application/rdf\+xml
RewriteRule ^(.+)/$ $1.rdf [R=303]
# Choose the default response
# ---------------------------
# Rewrite rule 4: to serve RDF/XML content by default
#RewriteRule ^(.+)/$ $1.rdf [R=303]
# Rewrite rules to serve HTML content by default
RewriteRule ^(.+)/$ $1.html [R=303]
When trying:
GET: http://example.com/ldExamples/catalog_001/
I receive http://example.com/ldExamples/catalog_001.html.html
With:
GET: http://example.com/ldExamples/catalog_001/
Accept: application/rdf+xml
I receive http://example.com/ldExamples/catalog_001.html.rdf.html
I know this has to do with looping. I tried adding L to [R=303]. I later found out I was receiving a 500 internal error because of the loop as well.
To debug further, I tried removing the loop and targeting a URL directly:
# Turn off MultiViews
Options -MultiViews
# Directive to ensure *.rdf files served as appropriate content type,
# if not present in main apache config
AddType application/rdf+xml .rdf
# Rewrite engine setup
RewriteEngine On
RewriteBase /ldExamples
# Rewrite rule 2: to serve HTML content from class or prop URIs if requested
RewriteCond %{HTTP_ACCEPT} !application/rdf\+xml.*(text/html|application/xhtml\+xml)
RewriteCond %{HTTP_ACCEPT} text/html [OR]
RewriteCond %{HTTP_ACCEPT} application/xhtml\+xml [OR]
RewriteCond %{HTTP_USER_AGENT} ^Mozilla/.*
RewriteRule ^catalog_001$ catalog_001.html [R=303]
# Rewrite rule 3: to serve RDF content is requested
RewriteCond %{HTTP_ACCEPT} application/rdf\+xml
RewriteRule ^catalog_001$ catalog_001.rdf [R=303]
# Choose the default response
# ---------------------------
# Rewrite rule 4: to serve RDF/XML content by default
# RewriteRule ^catalog_001$ catalog_001.rdf [R=303]
# Rewrite rules to serve HTML content by default
RewriteRule ^catalog_001$ catalog_001.html [R=303]
This returns http://examples.com/ldExamples/catalog_001.html regardless of Accept request. I tried adding L to the [R=303], but it also resulted in a 500 internal error.
Ultimately, I would like for some kind of variable setup, because I would like to serve multiple URIs and files.