Quinolizidines. XXXII. A Chiral Synthesis of 3,4,5,6-Tetradehydro-17-hydroxycorynanium, the Zwitterionic Structure Assigned to an Alkaloid from Aspidosperma marcgravianum

Article abstract of DOI:10.1016/S0040-4020(01)80544-5

The total synthesis of 3,4,5,6-tetradehydro-17-hydroxycorynanium <(+)-4>, the zwitterionic structure assigned to an alkaloid from Aspidosperma marcgravianum, has been accomplished for the first time via a "lactim ether route".The route started with initial condensation between the lactim ether <(+)-5> and 3-chloroacetylindole and proceeded through the lactam ester <(+)-23>, lactam alcohol <(+)-24>, acetoxylactam <(+)-26>, quaternary iminium salt <(+)-25>, and 3,4,5,6-tetradehydro-17-hydroxycorynanium perchlorate <(+)-27>.The 1H NMR spectral data and the sign of specific rotation for the synthetic (+)-4 were in disagreement with those reported for a natural sample, leaving the chemistry of this A. marcgravianum alkaloid incomplete.