Total Synthesis of the Kopsia lapidilecta Alkaloid (±)-Lapidilectine B

The total synthesis of Kopsia lapidilecta alkaloid (+/-)-lapidilectine B is described. Notable elements of this synthesis include the first natural products application of the Smalley azido-enolate cyclization to form the 1,2-dihydro-3H-indol-3-one (indoxyl) core and installation of the pyrrolidine ring by a 2-azaallyllithium [3+2] cycloaddition with the acetylene equivalent phenyl vinyl sulfide. Closure of the eight-membered perhydroazocine ring is accomplished via the intramolecular S(N)2 substitution of a mesylate. This constitutes the first synthesis of a member of the 5,6,12,13-tetrahydro-11a,13a-ethano-3H-pyrrolo[1',2':1,8]azocino[5,4-b]indole class of alkaloids.