Revised Structure and Convergent Synthesis of Nemertelline, the Neurotoxic Quaterpyridine Isolated from the Hoplonemertine Sea Worm

Article abstract of DOI:10.1021/jo00128a021

The correct structure of the quaterpyridine nemertelline first isolated from hoplonemertine sea worms has been identified as 2 (3,2':3',4'':2'',3'''-quaterpyridine).The natural product was synthesized using palladium(0)-catalyzed cross-coupling of 3-(tributylstannyl)-2,3'-bipyridine (3) and 4-chloro-2,3'-bipyridine (4).The bipyridines were prepared in the presence of the Pd catalyst by cross-coupling 2-bromo-3-(tributylstannyl)pyridine (5) and 2,4-dichloropyridine with 3-diethyl(pyridyl)borane, respectively.X-ray analysis confirmed the structure of 2 and provided its conformation in the solid state.The proton NMR spectrum of 2 identifies it as the natural product first reported in 1976.