Elucidation of the 1,3-Sulfanylalcohol Oxidation Mechanism: An Unusual Identification of the Disulfide of 3-Sulfanylhexanol in Sauternes Botrytized Wines

A four-step purification method was developed to isolate a citrus odorant detected by gas chromatography−olfactometry (GC−O), which was apparently specific to Sauternes botrytized wines. A fragmentation pattern of the odorant was obtained by multidimensional gas chromatography−mass spectrometry−olfactometry (MDGC−MS−O). The exact mass measurement was used to determine its elemental formula as C6H12OS. On the basis of these data, the unusual structure of 3-propyl-1,2-oxathiolane was synthesized and characterized for the first time. This confirmed its identification. Its occurrence in Sauternes wine extracts was demonstrated to result from the thermal oxidative degradation of 3-sulfanylhexanol disulfide (3,3′-disulfanediyldihexan-1-ol) in the GC injector. This disulfide was synthesized and then firmly identified for the first time in Sauternes wine. Although the presence of 3-sulfanylhexanol oxidation products had previously been reported in natural extracts (but not wine), the full oxidation pathway from 3-sulfanylhexanol to 3-propyl-γ-sultine via 3,3′-disulfanediyldihexan-1-ol was clearly established for the first time. Because the disulfide has mainly been detected in Sauternes botrytized wines, this finding suggested a singular reactivity of 3-sulfanylhexanol in botrytized wines, thus opening up a wide range of new opportunities in wine chemistry.