FIELD OF THE INVENTION
The present invention relates to the use of dihalomethanes as reagents for the preparation of Topotecan{4-(S)-10(dimethylamino)-methyl-4-ethyl 4,9 dihydroxyl-H-pyrano[3'4': 6,7]indolizino-[1,2-b]quinoline-3,14(4H,12H)dione} of formula I from hydroxycamptothecin. The invention