Dechlorinated rebeccamycin (II) was obtained by hydrogenolysis of rebeccamycin (I). Condensation of (II) with bromoacetyl bromide in the presence of potassium tert-butoxide in THF afforded a mixture of the title 3'-O-acylated compound (III) and the 2'-regioisomer (IV), which were separated by means of flash chromatography.