Abstract
A general synthetic strategy to ansa-macrocyclic lactam, maytansinoid, is described via a common intermediate for maytansine, maytansinol, maysine and N-methylmaysenine. The key reactions are focused on the successful stereochemical control by diastereoselective asymmetric induction involving heteroconjugate addition, epoxidation, aldol reaction etc. The principle was mainly based on chelational and conformational control in acyclic system, and all of the seven asymmetric centers of maytansinol has been introduced before closing 19-membered lactam ring.
