Total synthesis of alasmontamine A, a tetrameric indole alkaloid – TetraIndole

Multimeric monoterpene indole alkaloids from the genus Voacanga, Callichilia and Tabernaemontana are among the most complex alkaloids isolated from plants. Structures isolated from these related botanical genera belong to the bis-aspidosperma-(pseudo)-aspidosperma type of alkaloids. The emblematic congeners are vobtusine, callichiline, ervafoline and alasmontamine, an impressive tetrameric structure that will be the culminating synthetic target. A strategy to collectively synthetize different targets led on an expeditious preparation of two common monomer subunits (and their analogues) valorizing the expertise of the consortium on spiro-indolenines, biomimetic strategies and total synthesis of complex natural substances. The central tasks will be devoted to the assembly of the multimeric structures with a focus on the formation of spiro-cycles and cascade reactions. Chemoselective process are planned to selectively accede to specific multimers from the common precursors.