Madang-amine

Starting from a model 2-azabicyclo[3.3.1]nonane 101 (rings AC of madang-amines), in 2006 Yamazaki and Kibayashi reported a procedure for the construction of the unsaturated 11-membered E ring common to madangamines A-E." The synthesis involves a stepwise introduction of the unsaturated eight-carbon chain required for the closure of the E ring, which was performed by intramolecular reductive amination (Scheme 23). 

Taking into account that the specific rotation of synthetic (+)-madang-amine D, which has an unambiguous 2S, 5S, 9R, 12R absolute configuration, has the same sign as in the closely related madangamines A-C (see Table 1), the above synthesis confirmed the absolute configuration of these alkaloids. 

---