asterisk users - Nov 2013 - Dialing directly with username and password

It seems I am not finding the right syntax to dial directly using an
username/password. If I insert in my dialplan something like:

        12345 => {
              Dial(SIP/823*********:5***********@78.11.22.33/01342244560);
              hangup();
        }

Then I get:

[Nov 21 20:09:01] NOTICE[9069][C-0001689e]: chan_sip.c:29713
sip_request_call: Conflicting extension values given. Using
'823************' and not '01342244560'
  == Using SIP RTP TOS bits 184
  == Using SIP RTP CoS mark 5
    -- Called SIP/823*********:5************@78.11.22.33/01342244560
[Nov 21 20:09:01] NOTICE[12287][C-0001689e]: chan_sip.c:22914
handle_response_invite: Failed to authenticate on INVITE to '"Leandro
Dardini" <sip:100 at 91.11.22.33>;tag=as1c0d8470'
    -- SIP/78.11.22.33-000144c3 is circuit-busy
  == Everyone is busy/congested at this time (1:0/1/0)

Which is the correct syntax to use to dial directly with username and
password?

Leandro
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