Total synthesis of the neotropical poison-frog alkaloid (-)-205B.

[reaction: see text]. A stereocontrolled total synthesis of the neotropical poison-frog alkaloid (-)-205B (1) has been achieved, employing a dithiane three-component linchpin coupling, a one-pot sequential construction of the embedded indolizidine ring, and ring-closing metathesis (RCM) to arrive at the novel 8b-azaacenaphthylene ring system comprising the alkaloid. The synthesis proceeded with a longest linear sequence of 19 steps, affording (-)-1 in 5.6% overall yield.