Our lab has been smelling a lot like disturbed soil lately, due to my work with 2-ethylfenchol. The flavor and fragrance division of Aldrich is a good place to start when you need highly hindered tertiary alcohols. While many of the low-molecular weight tertiary alcohols are minty and camphor-like, Et-fenchol smells like dirt. Actually in the concentrated state it reeks similar to TBS-silanol, but stronger. In more diluted form though it has a clean smell of freshly dug-up moist earth – the smell is persistant and very convincing; a colleague asked me if he could wear ethylfenchol on his shroud when he goes to a Halloween party dressed as a mummy.
Turns out, 2-ethylfenchol prepared from (+)-enantiomer of fenchone has been developed with a specific purpose: as a substitute for geosmin – the terpenoid metabolite produced by soil bacteria that makes soil smell earthy. The earthy note is desirable in some compositions, i.e. for pipe tobacco flavoring, and since geosmin is rather hard to make cheaply a semisynthetic substitute was found. (Water utility companies are less fond of geosmin; the odor threshold of geosmin is incredibly low. Together with 2-methylisoborneol – another dirty-smelling terpenoid from soil bacteria/fungi – geosmin lends awful taste to tap water).
Et-fenchol from Aldrich comes in kosher grade, with a large seal from rabbi Gershon Segal on the bottle: