Extend standard web service for custom BO

Hello Experts,

I have a requirement where I have created a custom BO with some custom fields and added its embedded component as a new tab on the Lead TI.

Now we want to integrate these custom fields to the standard lead web service to replicate these custom fields into the backend CRM system.

I tried for Process Extension Scenario but it only works for the fields added to the extended bo. Could you please suggest on how this could be achieved.

Thanks and Regards,

Sumeet Narang