Catalyzes the penultimate step in the biosynthesis of rebeccamycin, an indolocarbazole alkaloid that inhibits topoisomerase 1. Has a wide substrate range, including staurosporine aglycone, EJG-III-108A, J-104303, 6-N-methyl-arcyriaflavin and indolo-[2,3-a]-carbazole. 4'-demethylrebeccamycin + H2O = beta-D-glucose + dichloroarcyriaflavin A Alkaloid biosynthesis. Belongs to the glycosyltransferase 28 family.