Structure/Odor Activity Studies on Aromatic Mercaptans and Their Cyclohexane Analogues Synthesized by Changing the Structural Motifs of Naturally Occurring Phenyl Alkanethiols

Following a structure/odor activity approach as previously published, the present study was focused on three aromatic thiols also identified as food odorants, namely 1-phenylethane-1-thiol, phenyl methanethiol, and 2-phenylethanethiol. Their structures were systematically modified to receive 16 new sulfur-containing benzene derivatives. A determination of odor thresholds indicated that none of its homologues elicited a lower odor threshold than 1-phenylethane-1-thiol, and an enantiospecific synthesis, elucidated that its ( S)-enantiomer turned out to be the compound with by far the lowest odor threshold of 0.00025 ng/L in air. Within the homologous series of the ω-phenylalkane-1-thiols as well as the 1-phenylalkane-1-thiols the threshold values increased constantly with an elongation of the side chain. Among the respective cyclohexane derivatives, the tendencies with respect to thresholds and odor properties were comparable. The odor thresholds and odor qualities of the aromatic thiols were quite similar to those of their heterocyclic analogues considered in a previous publication. In addition, spectroscopic data for 28 new sulfur-containing compounds were generated, which might be helpful in the identification of such sulfur containing odorants occurring in trace levels in foods.