How to create a substitute maps: Wildcard used for resolving substitution variables in notification messages

Hi experts, 

I need to add the request.access_group variable in a notification message which is sent when an escalation is created. So, I have thought of starting from the escalation table, then moving to quote table and then moving to request table, and from there getting the access group value. 

In my notification message, I have included {{request.access_group}}.

This is the Substitution map I have created which is giving an empty value in the email.

How can I get this to work?

Cheers,

Buddhima