First I've heard of Cyclone Scheme, not sure how I missed it before https://justinethier.github.io/cyclone/

Implements R7RS(-small). Web demo here: https://cyclone-scheme.netlify.app/terminal.html

Design doc: https://github.com/justinethier/cyclone/blob/master/docs/Writing-the-Cyclone-Scheme-Compiler-Revised-2017.md

Seems to have a lot in common with CHICKEN Scheme.