How do I "sudo -u anotheruser -i" in SFTP

Hi,
As soon as I log into Winscp session, I need to sudo as another user (such as oracleuser)
So tried a couple of different things:
1) in Advanced settings, Environment > SFTP I enter:

sudo -u oracleuser -i -c /usr/libexec/openssh/sftp-server

However, I get the error message:
Cannot initialize SFTP protocol. Is the host running a SFTP server?
If I only use /usr/libexec/openssh/sftp-server it works - because that's the path to our sftp server.
What am I doing wrong?

2) So tried this other way:
After I login as my userid, I select Commands > Open in Putty. Then I execute sudo -u oracleuser -i. I am able to sudo in Putty, but my Winscp session ignores that I sudo. (I know b/c It does not allow me access directories that oracleuser allows).
Please help. I do not have need to enter password when I sudo -u oracleuser -i
Thanks.

ihot wrote:

sudo -u oracleuser -i -c /usr/libexec/openssh/sftp-server

However, I get the error message:
Cannot initialize SFTP protocol. Is the host running a SFTP server?

Please attach a full log file showing the problem (using the latest version of WinSCP).

Thanks. I attach my DEBUG2 log file.

Again, /usr/libexec/openssh/sftp-server works in winscp in Advanced setting> Environment > SFTP

When I log into putty, I had to execute:
sudo -u oracleuser -i


Merry Christmas to you all!

The SFTP channel was started, so it looks like the sudo succeeded. Though it's hard to tell remotely.

Do you have access to server-side logs. Anything useful there?

As it turns out, our Linux admin had to enable terminal emulation for our oracleuser.
SFTP is working now - with sudo -u oracleuser /usr/libexec/openssh/sftp-server.
Thanks for your help.