Novel Silicon-Based Patchouli Odorants of the Trialkyl(1-hydroxy-1-methylethyl)silane Type: Design, Synthesis, and Olfactory Properties

• Published in: Chemistry : a European journal 2010-07, Vol.16 (25), p.7404-7421
• Main Authors: Sunderkötter, Astrid, Lorenzen, Sabine, Tacke, Reinhold, Kraft, Philip
• Format: Article
• Language: English
• Subjects: bioinorganic chemistry; Carbon; Chemistry; Crystallography, X-Ray; Derivatives; Economics; Exchange; Magnetic Resonance Spectroscopy; Models, Molecular; Molecular Structure; Odor thresholds; Odorants; Odors; Oil; Oils, Volatile - chemical synthesis; Oils, Volatile - chemistry; Olfactory properties; patchouli; seco structures; Silanes; Silanes - chemical synthesis; Silanes - chemistry; Silicon; Silicon - chemistry; Silicon compounds; Smell; Stereoisomerism; Structure-Activity Relationship; Structure-odor relationships; Synthesis
• ISSN: 0947-6539; 1521-3765; 1521-3765
• DOI: 10.1002/chem.201000549

tert‐Butyl(1‐hydroxy‐1‐methylethyl)dimethylsilane (5), a sila‐substituted seco derivative of the recently reported patchouli lead structure (4aR*,8aR*)‐1,1,8a‐trimethyldecahydronaphthalene‐4a‐ol (4), and a number of related trialkyl(1‐hydroxy‐1‐methylethyl)silanes and further derivatives, compounds 8–24, with different silicon‐bound substituents (Me, Et, iPr, cPr, tBu, iBu, cPent, vinyl, SiMe3) were synthesized and studied for their olfactory properties. All of the silanes studied exhibit at least one of the main patchouli odor descriptors ‘woody,’ ‘earthy,’ and ‘camphoraceous,’ and some even exhibit all of them. The silanes MeR2SiC(OH)Me2 (12) and R3SiC(OH)Me2 (14) (R=cyclopropyl) were found to resemble natural patchouli oil most closely, with an even lower odor threshold than the natural lead structure (−)‐patchoulol (1). To complete this structure–odor relationship study, the carbon analogues of 12 and 14 (Si/C exchange) were also prepared and characterized. Although they show similar olfactory properties to the silanes 12 and 14, the synthesis of the corresponding carbon analogues is far less straightforward than that of the silicon compounds, and only silanes 12 and 14 can be economically produced industrially. tert‐Butyl(1‐hydroxy‐1‐methylethyl)‐dimethylsilan (5), ein sila‐substituiertes seco‐Derivat der kürzlich beschriebenen Patchouli‐Leitstruktur (4aR*,8aR*)‐1,1,8a‐Trimethyldecahydronaphthalen‐4a‐ol (4), sowie eine Anzahl verwandter Trialkyl(1‐hydroxy‐1‐methylethyl)silane (8‐24) mit unterschiedlichen Silicium‐gebundenen Substituenten (Me, Et, iPr, cPr, tBu, iBu, cPent, Vinyl, SiMe3) wurden synthetisiert und in Hinblick auf ihre olfaktorischen Eigenschaften untersucht. Alle untersuchten Silane besitzen mindestens eines der Patchouli‐Hauptattribute ‘holzig’, ‘erdig’ und ‘campherartig’, einige sogar alle drei. Die Silane MeR2SiC(OH)Me2 (12) und R3SiC(OH)Me2 (14) (R=Cyclopropyl) kommen dem natürlichen Patchouliöl am nächsten und besitzen sogar niedrigere Geruchsschwellen als die natürliche Leitstruktur (−)‐Patchoulol (1). Um diese Struktur–Geruchs‐Analysen zu vervollständigen, wurden auch die Kohlenstoff‐Analoga von 12 und 14 (Si/C‐Austausch) hergestellt und charakterisiert. Obwohl sie ähnliche Geruchseigenschaften wie die Silane 12 und 14 zeigen, war ihre Synthese jedoch deutlich aufwändiger, so dass sich einzig die Silane 12 und 14 industriell ökonomisch herstellen lassen. Silicon‐enhanced “patchoulies”: Silane 2, designed as a sila‐seco structure o