Synthesis of Natural Compounds Based on the [3,7]-Diazabicyclo[3.3.1]nonane (Bispidine) Core

The [3,7]-diazabicyclo[3.3.1]nonane (bispidine) structure is found in several interesting naturally occurring alkaloids. The most representative components are the tetracyclic alkaloid (−)-sparteine and the tricyclic (−)-cytisine alkaloids. Their biological activities have been known for a long time. In the literature, different syntheses of both tetracyclic and tricyclic structures have been reported, especially in the last few years, when a number of new reports renewed the interest in these fascinating molecules. Bicyclic bispidine derivatives have been thoroughly investigated in recent times also for their applications as catalysts, metal chelating agents, and lately in coordination polymers chemistry. In this review, we describe the most relevant strategies for the synthesis of molecules based on the [3,7]-diazabicyclo[3.3.1]nonane core, related to (−)-sparteine and (−)-cytisine alkaloids.