A Total Synthesis of (±)-Leuconodines D and E

A new synthetic route
for a short synthesis of (±)-leuconodines
D and E was developed. The rapid construction of the diaza[5.5.6.6]­fenestrane
core was achieved through a sequence involving a Pd-catalyzed aerobic
oxidative Heck cross-coupling reaction for the construction of indole
δ-lactam containing a full-carbon quaternary center, an epoxidative
cyclization for the assembly of pyrroloindole, and a ring-closing
metathesis for the construction of the piperidine ring. As a result,
the total synthesis of (±)-leuconodine E (2) was
achieved for the first time within a 10-step linear sequence, and
a more concise total synthesis of (±)-leuconodine D (1) was accomplished within a 12-step linear sequence from the commercially
available tryptophol.