gambit : Gambit-C is a native Scheme to C compiler and interpreter ( https://gambitscheme.org/wiki/index.php/Main_Page )
guile : GNU Ubiquitous Intelligent Language for Extensions ( https://www.gnu.org/software/guile/ )
ikarus : Ikarus is a free optimizing incremental native-code compiler for R6RS Scheme. ( http://www.cs.indiana.edu/~aghuloum/ikarus/index.html )
Add an ebuild in portage :
The ebuild is now in the portage tree.
You can also use layman : emerge layman then layman -a lisp
For Paludis use this rsync : rsync://gentoo.zugaina.org/lisp-portage
If you have a problem : ycarus(-at-)zugaina.org