Diastereoselective total synthesis of (±)-trans-trikentrin A

Author(s)

Marcus Vinicius Craveiro

• Document type: Doctoral Thesis
• Press: São Paulo.
• Institution: Universidade de São Paulo (USP). Conjunto das Químicas (IQ e FCF) (CQ/DBDCQ)
• Defense date: 2009-03-11

Examining board members

Luiz Fernando da Silva Jr; Antonio Carlos Bender Burtoloso; Paulo Roberto Ribeiro Costa; Diogo Seibert Lüdtke; Leonardo José Steil

• Advisor: Luiz Fernando da Silva Junior

Abstract

This thesis presents a new approach toward the synthesis of cyclopenta[g]indoles using a ring contraction reaction mediated by thallium trinitrate (TTN) of a tricyclic olefin, bearing an indol unit. We could find reactional conditions where the thallium(III) salt was chemoselective, reacting on the cyclohexenic double bond without formation of C2-C3 indolic oxidation byproducts. Using the reaction above, we could accomplish the first diastereoselective total synthesis of (±)-trans-trikentrin A, which is an indolic alkaloid isolated from a marine sponge, in 20 steps and 2% of global yield. The key-step was a ring contraction reaction mediated by TTN in CH3CN with in situ reduction promoted by NaBH4. Under this condition the trans-1,3- dimethylcyclopentane moiety of the target molecule was achieved with good diastereoselectivity. The asymmetric hydrogenation of (E)-ethyl-3-(1-benzyl-4-ethyl-1H-indole-7-yl)-but-2- enoate was attempted using iridium catalysts were performed, aiming the synthesis of (+)-trans-trikentrin A. (AU)