Synthesis of the pentacyclic intermediate for dynemicin a and unusual formation of spiro-oxindole ring

Abstract

A pentacyclic compound was synthesized as an important intermediate of antitumor antibiotic dynemicins. The key step was the intramolecular Heck reaction using catalytic Pd reagent. During the course of the synthetic studies, an unusual spiro ring compound was found to be produced via intramolecular conjugate addition.