Collective Synthesis of <i>Lycopodium</i> Alkaloids and Tautomer Locking Strategy for the Total Synthesis of (−)-Lycojapodine A
作者:Houhua Li、Xiaoming Wang、Benke Hong、Xiaoguang Lei
DOI:10.1021/jo3017555
日期:2013.2.1
The collective totalsynthesis of Lycopodium alkaloids (+)-fawcettimine (1), (+)-fawcettidine (2), (+)-alopecuridine (4), (−)-lycojapodine A (6), and (−)-8-deoxyserratinine (7) has been accomplished from a common precursor (15) based on a highly concise route inspired by the proposed biosynthesis of the fawcettimine- and serratinine-type alkaloids. An intramolecular C-alkylation enabled efficient installation
Application of the Helquist Annulation in <i>Lycopodium</i> Alkaloid Synthesis: Unified Total Syntheses of (−)-8-Deoxyserratinine, (+)-Fawcettimine, and (+)-Lycoflexine
total synthesis of the Lycopodium alkaloids (−)-8-deoxyserratinine (7), (+)-fawcettimine (1), and (+)-lycoflexine (4) is detailed. The key features include a highly efficient Helquist annulation to assemble the cis-fused 6/5 bicycle, facile construction of the aza nine-membered ring system employing double N-alkylation strategy, providing access to the common tricyclic skeleton, asymmetric Shi epoxidation
The first enantioselective total synthesis of (−)-8-deoxyserratinine has been achieved in 15 steps fromenone 4 with 7% overall yield. The key features include a highly efficient Helquist annulation to furnish the cis-fused 6/5 bicycle, facile construction of the aza nine-membered ring system employing double N-alkylation strategy, as well as asymmetric Shi epoxidation, delivering the desired β-epoxide
A new alkaloid, lycoposerramine-B (1), containing an oxime function, was isolated from the club moss Lycopodium serratum Thunb. The structure of 1 was elucidated by spectroscopic analysis, including J-resolved HMBC spectroscopy, and confirmed by its synthesis from the known alkaloid, serratinine (3).