Total synthesis and study of myrmicarin alkaloids.

The myrmicarins are a family of air- and temperature-sensitive alkaloids that possess unique structural features. Our concise enantioselective synthesis of the tricyclic myrmicarins enabled evaluation of a potentially biomimetic assembly of the complex members via direct dimerization of simpler structures. These studies revealed that myrmicarin 215B undergoes efficient and highly diastereoselective Brønsted acid-induced dimerization to generate a new heptacyclic structure, isomyrmicarin 430A. Mechanistic analysis demonstrated that heterodimerization between myrmicarin 215B and a conformationally restricted azafulvenium ion precursor afforded a functionalized isomyrmicarin 430A structure in a manner that was consistent with a highly efficient, non-concerted ionic process. Recent advancement in heterodimerization between tricyclic derivatives has enabled the preparation of strategically functionalized hexacyclic structures. The design and synthesis of structurally versatile dimeric compounds has greatly facilitated manipulation of these structures en route to more complex myrmicarin derivatives.