Synthetic studies on phloroglucins: a new approach to the bicyclo[3.3.1]nonane system via the regioselective ring-opening of the methoxycyclopropane

A new synthetic approach to the bicyclo[3.3.1]nonane system, a common structure in a number of polyisoprenylated phloroglucinol derivatives (phloroglucins), has been developed. The key step in our approach is a ‘one-pot’ procedure of two successive reactions, the intramolecular cyclopropanation reaction which affords the tricyclo[4.4.0.05,7]dec-2-ene derivative and its methoxy group directed regioselective ring-opening reaction mediated by ZnCl2, producing the desired bicyclo[3.3.1]nonane as the sole product.