A Formal Total Synthesis of (±)-Kopsihainanine A Using a Raney-Cobalt Mediated Reductive Cyclization Route to Polyhydroquinolines

Perhydroquinoline 4, the product of a Raney-cobalt mediated reductive cyclization reaction, was readily converted into the cis-ring-fused perhydroquinoline 15 that could be epimerized to its trans-fused counterpart 2 on sequential treatment with iodosylbenzene then sodium borohydride. Tetracycle 2 is an advanced intermediate associated with a recently reported total synthesis of the alkaloid kopsihainanine A (1).