I am using the following cURL request to localhost which runs fine:
curl -u admin:e4d4face52f2e3dc22b43b2145ed7c58ce66e26b384d73592c -d \"{\\\"jsonrpc\\\": \
Curl is using HTTP Basic authentication by default. Your headers set in Postman are something different. Try using Basic Auth in Postman. It is in top panel, you fill in username and password and authorization header will be generated.