Benzo[b]fluorenes via indanone dianion annulation: Total synthesis of prekinamycin and progress towards kinamycins.

摘要

Our pursuit of the total synthesis of kinamycin antibiotics can be divided into two parts. In the first part, we developed a new methodology - indanone dianion annulation - for the rapid construction of the benzo[b]fluorene tetracyclic carbon skeleton. The high regioselectivity of this reaction ensured its efficiency in the total synthesis of prekinamycin. We further achieved a high-yielding installation of the diazo moiety, thus completing the total synthesis of prekinamycin. In the second part, using a Diels-Alder reaction with anthracene both as a protection step and a blocking auxiliary device, we conceived and implemented a stereoselective strategy to install the four contiguous stereogenic carbon centers of the D ring, and obtained several close precursors to kinamycins.