X-Cart 5 uses parts of Symfony (including the ORM library), but not the Symfony framework itself.
Unfortunately, the tool is a part of Symfony, not a part of Doctrine, and it is not included into X-Cart 5.
Here you can find articles on creating entity classes manually:
-
http://kb.x-cart.com/display/XDD/Understanding+Models
-
http://kb.x-cart.com/display/XDD/Creating+new+entity+--+Introduction+of+editable+ItemsList+in+admin+area