Abstract: The basic framework of spiro [4,5] decane was constructed by photo-cycloaddition of methyl 2,4-dioxopentanoate(1) to 1,5-dimethyl-6-methylenecyclohexene(2) and retro-benzilic acid rearrangement of the proto-[2+ 2]photocycloadduction to afford a spirocyclic compounds(3) having vetivan structure. The carbon-carbon double bond of the five-membered ring in compound 3 was selectively reduced by using zinc dust to give spirocyclic diketone 4. The exocyclic carbonyl group was protected and the cyclic ketone group was converted into methylene group to give important vetivan-type precursor 6. The title compound 11 as a mixture was obtained by Grignard reaction with methyl magnesium bromide. The phenylurethanes isomers 12,derived from compound 11 by reaction of hydroxyl group with phenylisocyonate,was isolated from each other. (±)-Hinesol and (±)-agarospirol were synthesized by reduction with lithium aluminum finally. This method shortened the synthetic line,simplified empirical processes and raised the overall yield in comparison with our preceding papers.

Key words: (±)-Hinesol, (±)-Agarospirol, Spirocyclic sesquiterpenoides, Total synthesis