Use regex in location to iis web application

Hello,
I have try to config nginx as reverse proxy to my IIS web application, I have a lot of web application in IIS.
I can do as below config

location /directory/ {
proxy_pass https://thcom2.thaicom.net/directory/;
}

It not work when user type /Directory. I have try to use regex, but it error.

location ~* /directory/ {
proxy_pass https://thcom2.thaicom.net/directory/;
}


error is nginx: [emerg] "proxy_pass" cannot have URI part in location given by regular expression,

Please advise me.