Synthesis of (±)-depentylperhydrohistrionicotoxin

Abstract

Palladium (0)-catalysed cyclisation of 3-acetoxy-1-(4-aminoalkyl) cyclohexenes provides convenient access to the 1-azaspiro [5.5] undecane ring system found in the histrionicotoxins. Hydroboration of the 7-butyl derivative (4; R¹= Buⁿ, R²= H) and oxidation of the purified borane adduct with trimethyl-amine oxide afforded N-benzyldepentylperhydrohistrionicotoxin, which was readily converted into (±)-depentylperhydrohistrionicotoxin by hydrogenolysis over palladium–carbon.