Total Synthesis of (±)-Rhynchine E

Contributor(s):

Erick M. Carreira

Vincent A. P. Ruf

Guo X.-F, Shao H, Ma Z.-H, Sun J, Zhou Q, Zhao Y.-M. * Shaanxi Normal University, Xi’an, P. R. of China
Bioinspired Collective Total Synthesis of (±)-Rhynchines A–E.

Org. Lett. 2024;
26: 3135-3139
DOI: 10.1021/acs.orglett.4c00727.

Crossref PubMed Google Scholar

› Further Information

PDF Download Permissions and Reprints

Key words

(±)-rhynchine E - Pictet–Spengler reaction - 1,2-migration - aldol addition - C–H oxidation - Krapcho decarboxylation

Significance

In 2021, a new class of structurally unique monoterpene indole alkaloids was isolated from Uncaria rhynchophylla, rhynchines A–E. Zhao and co-workers now report the first racemic total synthesis of rhynchine E as well as rhynchine A–D. A biosynthetic relationship of the rhynchines natural products to hirsuteine, which is also commonly found in the isolation plant, was proposed.

Comment

The synthesis commenced with the formation of tetracyclic triester E from pyridinium salt C, through a Pictet–Spengler reaction. Subsequent treatment with NaBH₃CN in AcOH, triggered conjugated reduction and a 1,2-migration, forming the core tetrahydroazepine G. The tetrahydrofuran ring of (±)-rhynchine E was formed via C–H oxidation using K₃[Fe(CN)₆].

#
#

Publication History

Article published online:
14 June 2024

Georg Thieme Verlag KG
Rüdigerstraße 14, 70469 Stuttgart, Germany

Permissions and Reprints