Comparative Analysis of the Olfactory Properties of Silicon/Germanium/Tin Analogues of the Lily‐of‐the‐Valley Odorants Lilial and Bourgeonal

Abstract

AbstractThe silicon/germanium/tin analogues of the lily‐of‐the‐valley odorants lilial (rac‐1 a), compounds rac‐1 b, rac‐1 c, and rac‐1 d, and bourgeonal (2 a), compounds 2 b, 2 c, and 2 d, were synthesized and characterized for their olfactory properties, including GC–olfactometry studies. Compounds rac‐1 a–c and 2 a–c possess a typical lily‐of‐the‐valley odor, whereas the stanna‐analogues rac‐1 d and 2 d, despite some floral aspects, clearly no longer belong to the lily‐of‐the‐valley family. In both series of the carbon/silicon/germanium/tin analogues studied, the lily‐of‐the‐valley odor decreases in the order of carbon<silicon<germanium<tin. A HEK293 cell line with stable tetracycline‐regulated expression of hOR17‐4 was generated to analyze recombinant hOR17‐4 activation by rac‐1 a–d and 2 a–d by using Ca2+ imaging. Bourgeonal (2 a) showed the highest activation potency, whereas lilial (rac‐1 a) and sila‐bourgeonal (2 b) exhibited lower activation potencies. Sila‐lilial (rac‐1 b), germa‐lilial (rac‐1 c), and stanna‐lilial (rac‐1 d), as well as germa‐bourgeonal (2 c) and stanna‐bourgeonal (2 d), did not activate heterologously expressed hOR17‐4 at the concentrations tested. The carbon/silicon/germanium/tin switch strategy thus showed that the stanna‐derivatives clearly exceeded the molecular dimensions of the odorant receptor(s) responsible for the recognition of lily‐of‐the‐valley odorants, although the receptor affinity was already affected with the sila‐ and germa‐analogues. These data could later be used in the qualitative and quantitative evaluation of computational receptor models.