Synthetic Studies On Poisonous Frog Alkaloid(-)-Histrionicotoxin

This thesis mainly focuses on the synthetic study toward poisonous frog alkaloid histrionicotoxin,which bears a unique 1-azaspiro[5.5]undecane skeleton and two enyne side chains.The formal synthesis of histrionicotoxin has been achieved through a novel nitroso-ene reaction to construct the key spiro ring system.Based on the recent work in our group about type-I and type-II nitroso-ene reactions,we further designed and explored the intramolecular nitroso-ene reaction of substrate embedded with conjugated diene,through which a new diene product and nitrogen-containing quaternary carbon center was obtained.Then the stereocenter of secondary alcohol was introduced by intermolecular nitroso-Diels-Alder reaction.After cleavage of the nitrogen-carbon bond,a highly diastereoselective reduction of alkene was successfully performed with Crabtree’s catalyst,where the directing effect by the free hydroxyl may play an important role.The terminal alkene was finally resumed through Cope elimination and thus the formal synthesis of histrionicotoxin was completed.