Process for the manufacture of intermediates in camptothecin production

A process for the manufacture of the compound of formula (1):

• comprising:
• a) reacting a compound of formula (I):
• with an amine of formula HNR2R3 to obtain a compound of formula (II):
• b) further reacting a compound of formula (II) with an ethyl-base to obtain a compound of formula (III):
• c) further reacting said compound of formula (III) with a compound of formula (IV):
• to obtain a compound of formula (V):
• d) further reacting said compound of formula (V) with ozone to obtain a compound of formula (VI):
• e) further reacting said compound of formula (VI) with a compound of formula (VII):
• and a base, to obtain a compound of formula (VIII):
• f) further reacting said compound of formula (VIII) with di(C1-C6)-alkylformamide, di(C1-C6)-alkylacetal or a compound of the formula (R7R8N)3—CH to obtain a compound of formula (IX):
• g) further reacting said compound of formula (IX) with ammonium acetate to obtain a compound of formula (X):
• h) further reacting said compound of formula (X) with alkali metal borohydrides and earth metal salts to obtain a compound of formula (XI):
• i) further reacting said compound of formula (XI) with concentrated mineral acids to obtain the compound of formula (1);
• wherein:
• R, R1, R7 and R8 independently from each other are (C1-C6)-alkyl;
• R2, R3 and R4 independently from each other are selected from the group consisting of (C1-C6)-alkyl and (C3-C7)-cycloalkyl;
• and
• R5 and R6 independently from each other are selected from the group consisting of (C1-C6)-alkyl and an aryl group.