(define-syntax definem
  (lambda (x)
    (syntax-case x ()
      ((_ (macro . args) body ...)
       #'(definem macro (lambda* args body ...)))
        ((_ macro transformer)
         #'(define-syntax macro
             (lambda (y)
               (syntax-case y ()
                 ((_ . args)
                  (let ((v (syntax->datum #'args)))
                    (datum->syntax y (apply transformer v)))))))))))


(definem (test lst #:optional (fun car))
  `(,fun lst))

(define lst (list 1 2 3 4))