Abstract Acylations of 1, 3-dimethyl-(1) and 1, 3, 7-trimethylpyrrolo [2, 3-d] pyrimidine-2, 4- dione (2) with anhydrides in the presence of trifluoroacetic acid proceed well to give in good yields the corresponding 7-acyl derivatives 3–11. The 6-trichloroacetyl derivatives 5 and 6