Here's one way of doing it:
Welcome to Racket v5.90.0.6.
-> (syntax-case #'(a b c d) ()
((x ...) (syntax->list #'(x ...))))
'(#<syntax:5:16 a> #<syntax:5:18 b> #<syntax:5:20 c> #<syntax:5:22 d>)
For more, see the syntax object operations section and the functions exported by syntax/stx
.