#$%^&*AU2020101059A420200723.pdf#####ABSTRACT The present invention relates to a preparation method for compounds shown in formula I. The compounds prepared by the method of the present invention have activity of inhibiting indoleamine 2,3-dioxygenase. [Ri] R2 Norl (1N-Cy2 N Cy1 -(CRaRb) A formula (I)