Development of the Intramolecular Prins Cyclization/Schmidt Reaction for the Construction of the Azaspiro[4,4]nonane: Application to the Formal Synthesis of (±)-Stemonamine
A TiCl4-promoted tandem intramolecularPrins cyclization/Schmidt reaction has been designed and developed to be an efficient method for the construction of the azaspiro[4,4]nonane. The present tandem protocol has been employed to construct the tricyclic azaquaternary skeleton (ring A, B, and C) of stemonamine.
The first total synthesis of structurally unique polycyclic phenolic meroterpenoids, ganocins B and C is reported. The synthesis features gold-catalyzed intramolecular cascade cyclization to construct the C/D ring bearing an angular methyl group, diastereoselective Michael addition, and acid-mediated one-pot Robinson cyclization/deprotection/isomerization.
A simple and efficient method for the synthesis of tricyclic chromones has been developed. In this approach, tricyclic chromones were synthesized from a diverse range of phenols and alkynes through a Sonogashira coupling and subsequent gold-catalyzed intramolecular dominocyclization.