Macrotricyclic core

A good example for such a situation is a recent report on the synthesis of the macrotricyclic core 63 of roseophilin [40,41]- RCM was able to form the rather strained ansa chain of this target molecule only after the cyclization had been biased by a conformational control element X which helps to bring the unsaturated chains closer together and lowers the enthalpic barrier during ring formation (Scheme 18). 

The first synthesis of the macrotricyclic core of roseophilin was carried out by A. Furstner and co-workers. intramolecular Friedel-Crafts acylation was used to close the third ring of the macrotricycle. 

Furstner, A., Weintritt, H. Total Synthesis of the Potent Antitumor Agent Roseophilin A Concise Approach to the Macrotricyclic Core. J. Am. Chem. Soc. 1997, 119, 2944-2945. 

Due to the prevalence and diversity of pyrrole and indole alkaloids and the limitations of space, no attempt will be made to describe all of the synthetic efforts in this area. Of those syntheses wherein the construction of a pyrrole ring was of major importance, most efforts were devoted to the marine polycyclic aromatic lamellarin class of alkaloids and total syntheses of lamellarins-D, -G, -K and -O <97X5951, 97AGE155, 97CC2259, 97CC207> were reported Although not a total synthesis, Furstner reported a Pd-mediated route to the macrotricyclic core of the anti-leukemia alkaloid, roseophilin <97JA2944>. 

---