The new synthesis of sesquiterpenoids 10-bromo-α-chamigrene

Abstract

The new synthesis of 10-bromo-α-chamigrene was achieved as follows; 6-methyl-5-heptene-2-one was transformed into corresponding thioacetals, and then successively treated with Cp 2Ti(P(OEt) 3) 2. The intermediate reacted with mono-ketal of cyclohexane-1,4-dione, and gave the carbonyl coupling product. It was then transformed into the key intermediate γ-bisabolene via deketalization, Grignard reaction, dehydration and then furnished the target molecule by polyene cyclization, with total yield 2%. All structures were confirmed by 1H NMR and 13C NMR. The final compound was confirmed by 1H NMR, 13C NMR and MS.