# Synthesis of a Functionalized Bicyclo[3.2.1]Octane: A Common Subunit to Kauranes, Grayananes, and Gibberellanes

## TL;DR

This paper describes a successful method to synthesize a shared building block found in three types of natural diterpenoids.

## Contribution

A novel synthetic route using ring-closing metathesis to build a bicyclo[3.2.1]octane scaffold common to kauranes, grayananes, and gibberellanes.

## Key findings

- An initial 1,4-sila-Prins cyclization approach failed, yielding an undesired 1,2-cyclization product.
- A successful synthesis was achieved in 8 steps using ring-closing metathesis (RCM).
- The resulting scaffold is a functionalized bicyclo[3.2.1]octane suitable for further natural product synthesis.

## Abstract

Kauranes, grayananes, and gibberellanes are three important diterpenoid families. These natural products all share a bicyclo[3.2.1]octane skeleton, with oxidation at very specific positions. In this manuscript, we describe the synthesis of a bicyclo[3.2.1]octane building block, which could serve as a potential intermediate for the synthesis of natural products from these three families. A first approach relying on a 1,4‐sila‐Prins cyclization was first explored, which required the selective functionalization of dihydrocarvone (via C─H activation and selective oxidation). This strategy resulted in a dead end when a 1,2‐cyclization product was obtained. An alternative strategy relying on ring‐closing metathesis (RCM) allowed to successfully achieve the synthesis of the desired scaffold in 8 steps from cyclohexenone.

A detailed account on the synthesis of a bicyclo[3.2.1]octane scaffold, common to the kaurane, grayanane, and gibberellane diterpenoid families, is reported. Our original strategy relying on a 1,4‐sila‐Prins cyclization proved unsuccessful. Learning from that, we designed an alternative strategy relying on ring‐closing metathesis (RCM), which ultimately led to the desired compound in 8 steps.