Total Syntheses of β-Carboline Alkaloids Manzamine C, Orthoscuticelline C, and Quassidine S.

A regioselective olefin hydrofunctionalization reaction of pavettine ( 4 ) with various nucleophiles was developed and used as the key step in the total syntheses of β-carboline natural products manzamine C ( 3 ), orthoscuticelline C ( 5 ), and quassidine S ( 6 ). In the 6-step total synthesis of manzamine C ( 3 ), an efficient two-step procedure, comprising a Wittig olefination reaction and a Fukuyama-Mitsunobu reaction, was devised for the synthesis of the N -macrocycle with a Z -olefin.