174092-76-3

The present invention is to prepare efficiently 2'-amino-5'-hydroxypropiophenone corresponding to the AB-ring part of camptothecin (CPT) skeleton and a tricyclic ketone corresponding to the CDE-ring part in order to provide efficiently CPT by the total synthesis, which is a starting material for irinotecan hydrochloride and various kinds of camptothecin derivatives, and to provide stably CPT and its derivatives.

A general and efficient synthesis of (20S)-camptothecin (1a) is reported. A key common intermediate containing the pyridone and lactone (DE) rings of camptothecin and most derivatives was constructed from 2-trimethylsilyl-6-methoxypyridine by a series of metalation reactions and a Heck cyclization to provide an achiral bicyclic enol ether. Sharpless asymmetric dihydroxylation followed by lactol oxidation and iododesilylation produced the key intermediate in 94% enantiomeric excess. Alkylation with prop-argyl bromide and a cascade radical reaction with phenyl isonitrile then produced 1a. About 20 other penta-and hexacyclic analogues of camptothecin with differing single or multiple substituents at C7, C9, C10, C11, and/or C12 were made by changing the propargylating agent and the isonitrile. Included among these are several drug candidates and the approved drugs topotecan and irinotecan. The synthesis of the prodrug irinotecan is a direct one that does not pass through the active metabolite. The use of ortho-trimethylsilyl-substituted isonitriles allows the regioselective synthesis of camptothecin analogues in cases where isomeric mixtures are formed from the parent isonitriles. The synthesis of the derivatives relies on the broad scope and functional group tolerance of the key cascade radical reaction.