Patent ID: 7126000

Claim:
A process for preparing a tricyclic ketone to synthesize camptothecin analogs, wherein from Compound (k): (wherein TMS is a trimethylsilyl group, and Me is a methyl group), or Compound (v): (wherein TMS is a trimethylsilyl group, and Me is a methyl group), Compound (l): (wherein TMS is a trimethylsilyl group, and Me is a methyl group) is produced; and from Compound (l) Compound (m): (wherein TMS is a trimethylsilyl group, and Me is a methyl group) is produced; and from Compound (m) Compound (n): (wherein TMS is a trimethylsilyl group, Me is a methyl group, and Et is an ethyl group) is produced; and from Compound (n) Compound (o): (wherein TMS is a trimethylsilyl group, Me is a methyl group, and Et is an ethyl group) is produced; and from Compound (o) Compound (p): (wherein TMS is a trimethylsilyl group, Me is a methyl group, and Et is an ethyl group) is produced; and from Compound (p) Compound (q): (wherein Me is a methyl group, and Et is an ethyl group) is produced; and from Compound (q) Compound (r): (wherein Me is a methyl group, Et is an ethyl group, and Pr is a propyl group) is produced; and from Compound (r) Compound (s): (wherein Et is an ethyl group, and Pr is a propyl group) is produced; and from Compound (s) Compound (t): (wherein Et is an ethyl group, and tBu is a t-butyl group) is produced; and from Compound (t) Compound (h): (wherein Et is an ethyl group) is produced, wherein the improvement comprises (1) a step to obtain Compound (l) that comprises mixing Compound (k), a lithiating agent, a formylation reagent and an iodination reagent.