Polysulfides, cyclic

Lenthionine has the characteristic shiitake flavor. It is formed from the precursor, lentinic acid 14 by complex reactions involving a C-S lyase enzyme.30 Cyclic polysulfides occur in other Basidiomycete mushrooms (Genus Micromp-hale and Colly bid), in some red alga, and in seeds of Parkia speciosa. The latter contain lenthionine and 1,2,4-trithiolane (1,2,4-trithiacyclopentane) 17 as well as compounds with 4, 5, or 6 sulfur atoms.31 These seeds are valued in Indonesia for a unique, onion-like odor. Djenkolic acid and dichrostachinic acid S -[(2-carboxy-2-hydroxyethylsulfonyl)-methyl]cysteine are converted by a C-S lyase enzyme to cyclic polysulfides djenkolic acid yields 1,2,4-trithiolane and 1,2,4,6-tetrathiepane the latter is also formed from dichrostachinic acid.32... 

A number of unusual cyclic polysulfides showing antibiotic activity against bacteria and fungi have been isolated from the red alga Chondria aalifomica ( ) and from the mushroom Lentinue edodes ( ). Both 34 (1,2,4,6-tetrathiepane) and 35 (1,2,3,5,6-pentathiepane or lenthionine) have been isolated from both sources, while 1,2,3,4,5,6 -hexathiepane, 36, was obtained from the mushroom and 27 (1,2,4-trithiolane), 2 (1,2,4-trithiolane 4-oxide),... 

Sulfur vulcanization leads to a variety of cross-link structures as shown in Figure 1. All the sulfur does not result in cross-links some of it remains as pendent accelerator polysulfide groups and internal cyclic polysulfides. These alternative structures do not contribute to load bearing or strength properties and are more prevalent in unaccelerated or weakly accelerated vulcanization systems. Additional heating can also reduce the polysulfide rank of the cross-links. In some elastomers, this leads to a larger number of cross-links. However, in natural mbber or its synthetic polyisoprene equivalent, the overall result is a loss of cross-links, especially at temperatures over 160°C. 

The hyperthermophilic archaea of the genus Thermococcus, isolated from marine hydrothermal systems, has been found to be a rich source of cyclic methylene-sulfur [135]. The prokaryotic archaea, established as the third domain of life in addition to eukaryotes and bacteria, grow under extreme conditions such as the absence of oxygen, temperatures of 100 °C and saturated salt solutions. Thus, 23 cyclic polysulfides (145-167) could be isolated from the intact cells of Thermococcus tadjuricus (strain Ob9) and T. mococcus acidaminovorans (strain Vc6bk) by using chemical screening methods. 

The structures of nine of these compounds were determined by spectroscopic methods, while those of the 14 remaining materials were established by GC-MS only. The compounds can be classified into four types (A to D) the 1,2,4-trithiolanes (145-154), 1,2,4,5-tetrathianes (155-157), 1,2,3,5,6-pentathiepanes (158-163), which are all generally quite stable compounds, and the monoalkyl-substituted polysulfides (164-167), which tend to disproportionate into sulfur and disubstituted cyclic polysulfides. These compounds are structurally related to the cyclic polysulfide compounds reported from red alga Chondria californica in 1976 [136] and to compound 168 (3-hexyl-4,5-dithiacycloheptanone) reported from the brown algae of the Dictyopteris genus in 1971 [137]. The latter compound has more recently been found to be a potent inhibitor of bee venom-derived phospholipase A2 (PLA2) [138]. 

Formation from silicon-containing cyclic polysulfides. 1090... 

The transient thioaldehydes can also be trapped with dienes giving the corresponding Diels-Alder adducts in good yields. These reactions are carried out in toluene under reflux. Milder conditions (reflux in dichloromethane or benzene) have been reported by Sato and Satoh for a similar transformation which involves cyclic polysulfides instead of elemental sulfur238 (equation 18). The aldehydes obtained were trapped in Diels-Alder reactions. 

Conformations of heterocyclic fragments of 1,3,5,2,4-trithiadiazepines and 1,3,5,2,4,6-trithiatriazepines are planar. Cyclic polysulfides possess as a rule in the chair conformation both in crystal (Section 13.17.5.4) and in solution... 

The first preparation and structure determination of optically pure cyclic polysulfides, 6,10-diethyltrithiolo[ ]ben-zopentathiepin monoxides, were described in 1997 <1997TL1607>. Then the oxidation reaction and properties of... 

Seven-membered rings with four and more heteroatoms attract attention because of their biological activity. An important class of compounds is that of the seven-membered cyclic polysulfides with five sulfur atoms, which are well known as lenthionine and varacin. 

Another preparative technique involves the ring-opening polymerization of cyclic polysulfides.56 For example, l-oxa-4,5-dithiacycloheptane polymerizes very rapidly at room temperature when treated with an aqueous sulfide (reaction (11)) ... 

Many desirable meat flavor volatiles are synthesized by heating water-soluble precursors such as amino acids and carbohydrates. These latter constituents interact to form intermediates which are converted to meat flavor compounds by oxidation, decarboxylation, condensation and cyclization. 0-, N-, and S-heterocyclics including furans, furanones, pyrazines, thiophenes, thiazoles, thiazolines and cyclic polysulfides contribute significantly to the overall desirable aroma impression of meat. The Maillard reaction, including formation of Strecker aldehydes, hydrogen sulfide and ammonia, is important in the mechanism of formation of these compounds. 

Heterocyclic compounds are primarily formed through non-enzymatic browning reactions. Recent studies of deep-fat fried food flavors led to the identification of pyrazines, pyridines, thiazole, oxazoles and cyclic polysulfides which had long-chain alkyl substitutions on the heterocyclic ring. The involvement of lipid or lipid decomposition products in the formation of these compounds could account for the long-chain alkyl substitutions. Model systems were used to study the participation of lipids in the formation of pyrazines, pyridines, thiophenes and cyclic polysulfides. 

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... 

It was a characteristic of small shrimp flavor that many varieties of cyclic polysulfides were formed during cooking. Some distinction in the composition of these heterocyclic substances were also observed among the shrimp species or from the treatment before heating, and led to the following conclusion the content of free amino acids should give the initiative for the formation pathway of the heterocyclic substances in small shrimps. 

The concentration of these compounds were not as high as that of thialdine however, as each compound had a characteristic odor like fuel gas or Allium plant, and the threshold values were low, they must also have had a significant effect on shrimp flavor. It is concluded that the formation of various cyclic polysulfides is important to obtain an characteristic cooked shrimp flavor. 

As previously mentioned, the main components of the volatiles from small boiled shrimp were pyrazines and cyclic polysulfides. The composition of the volatiles was roughly divided into two types, those with a higher content of pyrazines or with a higher content of cyclic polysulfides. The compositions of pyrazines, trithiolanes and dithiazine derivatives in the volatiles from boiled shrimps were calculated from the GC peak areas (1,4,7,27) and are shown in Figure 1. 

The contents of trithiolanes and dithiazines were larger than that of pyrazines in raw lucens and A japonicus, both of which belong to the same taxonomical group. Conversely, in raw Antarctic krill, alkylpyrazines comprised the predominant part of the volatiles with few cyclic polysulfides also present. The composition of precooked krill corresponded to that of lucens, and that of fermented A. japonicus to raw krill. 

It is possible that this polymer is formed by ring-opening polymerization of the cyclic pentasulfide or other cyclic polysulfides. In a separate experiment, heating the trisulfide gave a similar chain polymer. We have not been able to separate the fraction VRE = 0.72 which was formed in much smaller quantities than other fractions. 

First, the sulfur atom from a thiirane is added to one of the carbon atoms of the thiirane ligand of the complex, with formation of a zwitterionic intermediate. The zwitterionic intermediate undergoes elimination of ethylene to yield a reactive alkene disulfide tungsten complex. The dithietane ligands from two or more molecules, then combine to form the cyclic polysulfides. If the macrocyclization of thiirane catalyzed by W(CO)s(SC2H4) is performed in the presence of DMAD, small quantities of polythioether macrocycles 156 and 157 are formed <1997OM1430>. 

---