The present invention relates to a method for the synthesis of 7-ethyl-10-[4-(1-piperidino)-1-piperidino]carbonyloxycamptothecin (i.e. iriniotecan), comprising: (a) preparing 10-[4-(1-piperidino)-1-piperidino]carbonyloxycamptotecin； and (b) selectively ethylating the compound of step (a) at the 7-position, thus resulting in the preparation of 7-ethyl-10-[4-(1-piperidino)-1-piperidino]carbonyloxycamptothecin. The present invention is further directed to the use of 10-[4-(1-piperidino)-1-piperidino]carbonyloxycamptothecin (i.e. 7-des-ethyl-irinotecan) as intermediate in a method for the synthesis of irinotecan as described.
