Structure‐Odor Correlation XVII. Synthesis and Olfactory Properties of further Theaspirane Analogs

Alkylation of ethyl geranate ( 5 ) with the bromo esters 7 and 8 gave the β,γ‐unsaturated esters 10 and 11 , which could be isomerized to 13 and 14 by treatment with DBU. The α,β‐unsaturated esters 12 – 14 were cyclized to 15 – 17 , and subsequent reduction of 15 – 17 led to the diols 18 – 20 . Final cyclization afforded the spiro ethers 2 – 4 . – The olfactive properties (intensity and quality) of the theaspirane analogs 1 – 4 are determined by the conformational flexibility of the respective molecule. Thus, the rigid 1 and 2 have strong camphoraceous odors. Augmenting flexibility (→ 3 , → 4 ) results in weaker, fruity‐woody notes.