Synthesis of Unnatural Alkaloid-Type Compounds from Terpenoid-Derived Natural Products by Nitrogen Insertion via Aminocyclization
Szeto, Howard Chung-Ho
The synthesis of unnatural alkaloid-type compounds from natural products using an oxidative alkene cleavage, reductive aminocyclization sequence was explored. The natural product cholesterol, as the initial model, was treated with ozone to cleave the 5, 6-alkene, forming the B-ring seco ketoaldehyde. Various reaction conditions were then tested with 4-methoxybenzylamine as primary amine source to optimize the reductive aminocyclization reaction. It was found that running this reaction in THF at 60˚C for one hour in the microwave provided a yield of 70%. Using this protocol, the reaction of cholesterol derived ketoaldehyde with various other primary amines gave mixed results.
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