The reduction of camptothecin (I) with H2 over PtO2 in acetic acid, followed by oxidative acylation with lead tetraacetate and acetic acid and hydrolysis with acetic acid/water gives 9-hydroxycamptothecin (II), which is then treated with formaldehyde and dimethylamine in acetic acid. The hydrochloride salt is prepared by treatment of the acetic acid solution with diluted HCl.