[racket] macro expansion function in Scheme

Ciao a tutti,

I'm looking for a Scheme function that can perform macro expansion on a 
quoted expression. I bet someone has implemented such a thing before, 
but I can't find it. Maybe someone can point me in the right direction?

For example, I'm looking for something that works along the following lines:

; example of syntax (from R5RS)
(define or-syntax
   '(define-syntax or
      (syntax-rules ()
        ((or) #f)
        ((or test) test)
        ((or test1 test2 ...)
         (let ((x test1)) (if x x (or test2 ...)))))))

; gather all quoted define-syntax expressions here
(define *syntax*
   (list or-syntax #;...))

; the function I'm looking for
(define (expand-macro expr syntax-lst)
   ??)

And then it could work like this:
 > (expand-macro '(or x y) *syntax*)
(let ((g42 x)) (if g42 g42 y))


Best regards,
Bas