First Identification of O,S-Diethyl Thiocarbonate in Indian Cress Absolute and Odor Evaluation of Its Synthesized Homologues by GC-Sniffing

Abstract

Indian cress (Tropaeolum majus L.) absolute was studied by GC-olfactometry (VIDEO-Sniff method) in order to identify odor-active aroma compounds. Because of its fruity-sulfury odor note, a compound that has never been identified in plant extracts before stood out: O,S-diethyl thiocarbonate, present at 0.1% (percentage of the total GC/FID area) in the extract. GCxGC-TOFMS allowed for a clean mass spectrum to be obtained, and isolation by preparative GC followed by NMR studies allowed its identification. Here, we report on the first detection of O,S-diethyl thiocarbonate in Indian cress absolute by GC-olfactometry/VIDEO-Sniff and on its isolation and identification. The synthesis and odor evaluation of its homologues are presented.

Synthesis of Unsymmetrical Thioethers Using an Uncommon Base-Triggered 1,5-Thiol Transfer Reaction of 1-Bromo-2-alkylthiolcarbonates

“…We were now ready to apply the newly developed 1,5-thiol transfer reaction to the synthesis of the sugar functionalized thiacalix [4]rene at the origin of the present work. This would require that an appropriate tetrathiolcarbonate undergo four 1,5-transfer reactions simultaneously to install the four sugar thioether functions required on the central thiacalix [4]rene core (Scheme 8).…”

“…We were now ready to apply the newly developed 1,5-thiol transfer reaction to the synthesis of the sugar functionalized thiacalix [4]rene at the origin of the present work. This would require that an appropriate tetrathiolcarbonate undergo four 1,5-transfer reactions simultaneously to install the four sugar thioether functions required on the central thiacalix [4]rene core (Scheme 8). Thiacalix [4]arenes are a subclass of "third generation" calixarenes and exhibit a number of interesting features compared to the oxygenated counterparts, such as enlarged ring size and differing metal complexation potential, due to the presence of its bridging sulfur atoms.…”

“…For instance, reagents such as native sulfur S(0), Na 2 S 2 O 3 , thiourea, or trialkylsilyl-protected thiols have been efficiently reacted with alkyl and/or aryl halides, with or without metal catalysis, to obtain the target unsymetrical alkyl or arylthioether derivatives. 2 In a project related to the investigation of bacterial adhesion events we required a convenient synthesis of a number of sugarderived unsymmetrical thioethers and in particularly of sugarfunctionalized thiacalix [4]erene such as the tetravalent glucose analogue described herein (Figure 1). Although several disconnections evoking various sulfur sources might be proposed to access such a tetravalent construct, we were particular drawn to developing a method exploiting as a key step the thiolcarbonate (RSC(O)OR) function.…”

“…This increases the versatility of the approach, as a very large variety of complex triazole-tethered substrates can potentially be integrated into the target unsymmetrical thioether final products. As an example of the scope of the reaction, four 1,5-shift reactions have been triggered simultaneously from a sugarderived tetrathiolcarbonate precursor using base catalysis, to allow four 6-thioglucose moieties to be installed (78% yield for each sugar unit) onto a 1,3-alternate thiacalix [4]arene scaffold in a one-pot transformation.…”

Advances of Modern Gas Chromatography and Hyphenated Techniques for Analysis of Plant Extracts

“…Recently, comprehensive GC has allowed the identification of a compound (O,S-diethyl thiocarbonate) never reported before in plant extracts and characterized by a fruity-sulfury note [97]. The plant from where it has been isolated is the Tropaeolum majus L., also known as Indian cress.…”