# Synthesis of the ABC Core of Daphniphyllum Alkaloids with a [5–6–7] Azatricyclic Scaffold via Ring Expansion of Azabicyclic and Azatricyclic Building Blocks

## TL;DR

Scientists developed a new way to synthesize a complex core structure found in Daphniphyllum alkaloids using ring expansion and radical closure methods.

## Contribution

A novel synthetic route for the [5–6–7] azatricyclic ABC core of Daphniphyllum alkaloids is introduced.

## Key findings

- A perhydroindolone ring expansion was used to form the AC ring system.
- A radical B ring closure was a key step in the synthesis.
- Homomorphans were synthesized for the first time via ring enlargement of 2-azabicyclo[3.3.1]nonanes.

## Abstract

The [5–6–7] azatricyclic ABC core, found
in several Daphniphyllum alkaloids, has been synthesized
through a
novel route involving ring expansion of a perhydroindolone to afford
the AC ring system and a radical B ring closure as key steps. The
level of functionalization of the reported octahydro-1,7-ethanocyclohepta[b]pyrroles suggests that they can serve as valuable building
blocks in this alkaloid field. Also reported is the first synthesis
of homomorphans by the ring enlargement of 2-azabicyclo[3.3.1]nonanes.