Dimethyl-trithiolane

Durian (Durio zibethinus) Dimethyl trithiolane, methylbutanoate Ascorbigen, bisabolene. Guava (Psidium guajava) cadinene, cinnamyl-acetate, ellagic acid, humulene,... 

Trithiolane, 3,5-dimethyl-biological activity, 6, 895 occurrence, 6, 895 reactions... 

The most important sulfur heterocycles with a five-membered ring and three sulfur atoms are the diastereomeric 3,5-dialkyl-1,2,4-trithiolanes 6. The dimethyl derivatives (6, R - Me) have been found in various cooked foods, such as mushrooms (41), boiled beef (42) commercial beef extract (43), boiled antarctic krills (44), red algae (45), and several model systems containing a source of sulfur (2,19,29), The diethyl derivative (6, R - Et) was identified by Ledl (33) and by Sultan, with propionaldehyde as the starting material. The dipropyl and diisopropyl derivatives (6,... 

This important flavor compound was identified in the head-space volatiles of beef broth by Brinkman, et al. (43) and although it has the odor of fresh onions, it is believed to contribute to the flavor of meat. This compound can be formed quite easily from Strecker degradation products. Schutte and Koenders (49) concluded that the most probable precursors for its formation were etha-nal, methanethiol and hydrogen sulfide. As shown in Figure 5, these immediate precursors are generated from alanine, methionine and cysteine in the presence of a Strecker degradation dicarbonyl compound such as pyruvaldehyde. These same precursors could also interact under similar conditions to give dimethyl disulfide and 3,5-dimethyl-l,2,4-trithiolane previously discussed. 

Cyclic Polysulfides 3.5- dimethyl-1,2,4-trithiolane (isomer) 3.5- dimethyl-1,2,4-trithiolane (isomer) 3-methyl-5-pentyl-l,2,4-trithiolane 2.4.6- trimethylperhydro-l,3,5-thiadiazine 2.4.6- trimethylperhydro-l,3,5-dithiazine 2,4-dimethy1-6-pentylperhydro-l,3,5-dithiazine 2-pentyl-4,6-dimethylperhydro-l,3,5-dithiazine 122.8 18.2 14.3 828.5 284.2 18.9 28.7... 

Trithiolanes have received increasing attention since the identification of diastereomeric 3,5-dimethyl-l,2,4-trithiolane in the volatiles of boiled beef (13). The parent 1,2,4-trithiolane is a component of Shiitake mushrooms (14) and red algae (15). In addition to 3,5-dimethyl-l,2,4-trithiolane, Kubota et al. (16) identified 3-methyl-5-ethyl-l,2,4-trithiolane and 3,5-diethyl-l,2,4-tri-thiolane in both syn and anti forms in boiled Antarctic Gulls. Both compounds were described as garlicky. Flament and co-workers (17) reported the identification of 3-methyl-5-ethyl-l,2,4-trithiolane and 3-methyl-5-isopropyl-l,2,4-trithiolane in a commercial beef extract. ... 

In addition to 3,5-dimethyl-l,2,4-trithiolane and 3,5-diiso-butyl-l,2,4-trithiolane, the two long-chain alkyl-substituted trithiolanes, 3-methyl-5-butyl-l,2,4-trithiolane and 3-methyl-5-pentyl-... 

The volatile components identified from the reaction of cystine and DMHF in aqueous medium are shown in Table I. 2,4-Hexanedione, 3,5-dimethyl-l,2,4-trithiolanes and thiophenes are the major compounds. The mechanistic relationship of the three thiophenones produced has been postulated (23). The major groups of volatile components identified from the reaction in the glycerol medium are 1,3-dioxolanes and thiazoles (Table II). 1,3-Dioxolanes are formed by the reaction of glycerol and the degraded carbonyls by ketal or acetal formations. Comparison of the reaction of cystine and DMHF in water and in glycerol is outlined in Table III. 

The effect of reaction time on the major components of the reaction of cystine and DMHF in water is shown in Table IV. It is noteworthy that amounts of 2,4-hexanedione, 3,5-dimethyl-l,2,4-trithiolanes and thiophenones were found at a maximum after one hour. It was also found that the amount of 2-acetylthiazole increased with time and that acetol acetate decreased with time as expected. In the glycerol medium, the effect of reaction time on the major components is shown in Table V. Apparently, the 1,3-dioxo-lane, which is a ketal formed from glycerol and acetone, decreased over time. Also, long reaction time favors the formation of cyclic compounds, including 2,5-dimethyl-2-hydroxy-3(2H)-thiophene, cyclo-pentenones and 4,5-dimethyl-l,2-dithiolenone. 

The water content significantly affects the formation of some compounds. Figure 2 shows that the formation of thiazoles decreases as the water content increases. Figure 3 shows the relationship between water content and the formation of a 3,5-dimethyl-1,2,4-trithiolane, 3-hydroxy-pentanone and 2,4-hexanedione. The highest level of trithiolanes was obtained from the sample prepared with 75% water. Figure 4 shows that these three thiophenones were also produced at maximum at 75% water medium. 

Figure 3. The effect of water content on the formation of 3,5-dimethyl-l,2,4-trithiolane, 3-Hydroxy-2-pentanone and 2,4-Hexanedione from the reaction of cystine and DMHF.

The optimal conditions for generating the major products formed from cystine and DMHF are as follows 3,5-dimethyl-l,2,4-trithio-lane, thiophenones and 2,4-hexanedione are all found preferentially in an aqueous medium heated to 160°C. The trithiolane and thiophe-none are optimized at 75% H2O and pH 4.5, while 2,4-hexanedione formation is better at 100% H2O and lower pH. Thiazoles, on the other hand, require a higher temperature and a nonaqueous medium. 

As a result of the reaction parameter study, the products, aromas and chemistry of the reaction between cystine and DMHF is more clearly understood. The major volatile components generated by this reaction are 3,5-dimethyl-l,2,4-trithiolanes, thiophenones, thia-zoles and 2,4-hexanedione. The first three groups of compounds contribute greatly to the quality of the overall aroma which is roasted, meaty and burnt. Further variations in aromas may depend on the proportions of these components present as reaction products. Optimal conditions for producing the major components of interest from the title reaction have been determined. 

Dimethyl-l,2,4-trithiolane (126) reacted with methyllithium at -60 °C to give intermediate (127) which was transformed into 4,6-dimethyl-2,3,5,7-tetrathiaoctane (128) in the presence of excess dimethyl disulfide (78HCA2809). Compound (128) is a constituent of roasted pork meat (c/. Section 4.33.5.2). 

These compounds, produced in the reaction of H2S and ethanal, have been detected in a synthetic solution and in a white wine by Rauhut and Dittrich (1993). These authors made H2S at concentrations from 1 to 5 mg/L react with ethanal at variables concentrations from 100 to 500 mg/L. This reaction produces cis-ltrans-3,6-dimethyl-1,2,4,5-tetrathiane, the cw-/fran -4,7-dimethyl-l,2,3,5,6-pentathiepane and the c -/fran -3,5-dimethyl-l,2,4-trithiolane and the precursor of these compounds, 1,1-ethanedithiol. However, the same reaction with copper does not prevent formation of these compounds. In contrast, the reaction reported by some authors between H2S and ethanal to form ethanethiol, does not take place. 

Two experiments were performed to try to determine which of these reactions was occurring. After macerating the red wine grapes for one day the coloured must obtained was seeded with yeasts (100 mg/L of LSA). Also, a commercial white must was seeded with the same dose of yeasts. When fermentation started, 5 mg/L of H2S were added and the analysis was carried out one week after finishing alcoholic fermentation. In both cases, the formation of cw-/fran.y-3,6-dimethyl-1,2,4,5-tetrathiane and of cA-//ran.y-3,5-dimethyl-1,2,4-trithiolane was detected. The mass spectra are shown in Figs. 10.9 and 10.10. By contrast, in this experimentdx-Z/rani-4,7-dimethyl-1,2,3,5,6, pentathiepane and 1,1-ethanedithiol did not appear. 

Isomers of these compounds have very similar retention times in these conditions (Fig. 10.11). With a polar column, the cw-/fran -3,5-dimethyl-1,2,4-trithiolane exit first, followed by cA-//ran.y-3,6-dimethyl-1,2,4,5-tetrathiane. 

Fig. 10.10 Mass spectra of 5-dimethyl-1,2,4-trithiolane. At the centre is the mass...

These compounds were not found in the wines studied. Nonetheless, some were detected in a grape marc spirit with a clear reducing defect in which we detected the presence of cw-/fran -3,5-dimethyl-1,2,4-trithiolane and cw-/fran.y-3,6-dimethyl-1,2,4,5-tetrathiane, although neither di-/fran.y-4,7-dimethyl-1,2,3,5,6-pentatiepane nor 1,1-ethanedithiol were detected. These compounds could possibly come from the base wine used for the distillation, although it is prohibited to use SO2 in wines used for this purpose. The hypothesis according to which ethanal is free to react with H2S is, therefore, reinforced. 

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