Process of preparing camptothecin derivatives

A process of preparing a compound of formula 1, or a salt thereof,

• the process comprising:
• (a) reacting a compound of formula 2
• wherein
• Y and Z are independently chosen from —H, a C1 to C6 alkyl group, a C1 to C3 hydroxyalkyl group, and an amine protecting group;
• R1 is selected from —H, a C1 to C6 alkyl group and a hydroxy group;
• R2 and R3 are independently selected from —H and hydroxy, or taken together form a methylenedioxy or ethylenedioxy group;
• R4 is selected from —H and a C1 to C6 alkyl group;
• and
• R5 is selected from —H, hydroxy, halogen and amine with an amine, or salt thereof, and a source of formaldehyde in the presence of an acid;
• and
• (b) obtaining a compound of formula 1, or a salt thereof.