Studies on the Total Synthesis of Lactonamycin: Synthesis of the CDEF Ring System

摘要

A concise and efficient synthesis of the tetracyclic CDEF ring system of lactonamycin (1) is described.The key step involved the Lewis acid mediated,intramolecular Friedel-Crafts acylation of carboxylic acid 6 to produce the tetracyclic CDEF core structure of target 1.The synthesis of 6 was carried out using a high-yielding Negishi coupling of benzyl bromide 7 with triflate 8,which was accessible in 11 steps and 31% overall yield on a multigram scale starting from trihydroxy acid 9.