I tried this:
curl -L https://api.box.com/2.0/folder/FOLDER_ID/items -H "Authorization: Bearer AUTH_KEY"
Error:
{"type":"error","status":401,"code":"unauthorized","help_url":"http:\/\/developers.box.com\/docs\/#errors","message":"Unauthorized - Cannot authorize with this service","request_id":"l7g1fffudda0ncc