Synthesis Of Thiols Research Articles

Elevated thiol levels affect virus infection inCucurbita pepoplants regenerated via somatic embryogenesis

Thiols are known to play crucial roles in plant defense responses, e.g. against pathogens. In the present study, the efficiency of these molecules was evaluated in regenerated Cucurbita pepo L. subsp. pepo var. styriaca Greb. plants in response to compatible Zucchini yellow mosaic virus infection. Thiol contents were modulated by applying the cysteine precursor L-2-oxothiazolidine-4-carboxylic acid (OTC) to callus cells. Cytological and biochemical methods were used for determination of glutathione within callus cells and leaves of plants regenerated via somatic embryogenesis. Reduced glutathione levels (GSH) significantly increased in callus cells one week after 1.0 mM OTC treatment by about 56% and resulted in enhanced GSH levels throughout the investigation period of 13 weeks. Three weeks after ZYMV infection untreated plants regenerated from callus culture exhibited stunted growth forms, yellowing, mosaic and blistering on the leaves whereas 68% of 1.0 mM OTC pretreated regenerated plants were characterized by a complete absence of symptoms. Treatment with OTC stimulated the synthesis, conversion and translocation of thiols during advanced ZYMV infection. Compared to untreated infected leaves, a graduate increase in cysteine (cys) and γ-glutamyl-cysteine (γ-glucys) contents was measured in 0.5 mM and 1.0 mM OTC treated older leaves, whereas total glutathione (tGSH) decreased significantly after infection. In OTC treated younger leaves cys and tGSH concentrations remained at control levels and were unaffected by ZYMV. In contrast, OTC treatment caused a dramatic induction of γ-glucys, up to 191% in younger infected leaves. The results show that altered levels of thiols by OTC were accompanied by enhanced tolerance against ZYMV, suppression of ZYMV induced symptoms as well as delayed symptom development.

O‐Alkyl S‐3,3‐Dimethyl‐2‐oxobutyl Dithiocarbonates as Versatile Sulfur‐Transfer Agents in Radical C(sp3)H Functionalization

Boiling of the title compounds in ethereal solvents or cycloalkanes in the presence of a radical initiator leads to radical C(sp3)-H functionalization, by which a sulfur atom is introduced into the ethereal solvents at the oxygenated carbon atom or into the cycloalkanes. Both acyclic and cyclic ethers, such as [18]crown-6 and [D8]THF, undergo the sulfur transfer. The reaction is useful for the synthesis of monothioacetals, thiols, and sulfides from simple starting materials.

Synthesis and Reactivity of Fluorine‐Containing Thiols and Thioacyl Halides.

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MMTr as an Efficient Anomeric S‐Protecting Group for the Synthesis of Glycosyl Thiols.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF.

Synthesis, characterization and electrochemical behavior of unsymmetric transition metal-terminated biphenyl ethynyl thiols

The synthesis of the biphenyl alkynyl thiols and thioesters R′–C C–C 6H 4–C 6H 4–SR ( 3: R′ = SiMe 3, R = C(O)Me; 4: R′ = SiMe 3, R = H; 5: R′ = H, R = C(O)Me) from I–C 6H 4–C 6H 4–SC(O)Me ( 1) is described. Molecules 1 and 5 have been used as starting materials in the synthesis of mono- and heterobimetallic transition metal complexes of type L n M′–C C–C 6H 4–C 6H 4–SR ( 7: L n M′ = Fc, R = C(O)Me; 8: L n M′ = Fc, R = H; 10: L n M′ = (Ph 3P)Au, R = C(O)Me; 14: L n M′ = FcPPh 2-Au, R = C(O)Me; Fc = (η 5-C 5H 5)(η 5-C 5H 4)Fe; FcPPh 2 = (η 5-C 5H 5)(η 5-C 5H 4PPh 2)Fe). While complex 7is accessible by the Sonogashira cross-coupling of Fc–C CH ( 6) with 1, molecules 10 and 14 can be prepared by treatment of the thioester 5 with (Ph 3P)AuCl ( 9) and FcPPh 2-AuCl ( 13), respectively. The molecular solid state structures of 3, 7, 10 and 13– 15 have been determined by single crystal X-ray crystallographic analysis. Typical features of these species are their linear M-C C–C 6H 4–C 6H 4–SR structure and the lack of coplanarity of the biphenyl arene rings. The overall length of these complexes are 13.345(2) Å for 3 (molecule A), 15.146(3) Å for 7, 15.705(2) Å for 10 (molecule A) and 15.649(4) Å for 14. The thioester groups are pointing away from the ferrocene building block. In 7 a linear 1D chain is set-up by π-interactions between two independent molecules of 7. Characteristic for 15 is the formation of a Au 2I 2 ring, while 13 is monomeric. All compounds were studied with cyclic voltammetry. Characteristic are the reversible ferrocene Fe(II)/Fe(III) redox wave, the irreversible reduction of Au(I) to Au(0), the oxidative cleavage of the S–C(O)Me sulfur–carbon ( 3, 5, 7, 10 and 14) and of the sulfur–hydrogen bond ( 4 and 8), respectively. Electronic effects extending from the –SH-end group to the ferrocene unit resulting in considerable shifts of the redox potential of the latter entity are found. Coordination of Au(I) at the FcPPh 2 moiety also results in a shift of the redox potential of the ferrocene group indicative of an electron withdrawing effect of the Au(I) species.

MMTr as an efficient anomeric S-protecting group for the synthesis of glycosyl thiols

The 4-monomethoxytrityl (MMTr) group was introduced in high yields to anomeric sulfhydryl functions using commercially available MMTrCl. Significantly, it is stable to a variety of reaction conditions, including acids and bases, and is removable under very mild acidic conditions, which are compatible with the presence of a number of other acid-labile hydroxyl protecting groups. The successful preparation of seven glycosyl thiols indicates that MMTr has potential application for the synthesis of complex 1-thiosugars.

Synthesis and reactivity of fluorine-containing thiols and thioacyl halides

A route to α-hydropolyfluoroalkanethiols and polyfluorothioacyl halides via thermal splitting of benzyl polyfluoroalkyl sulfides under the action of phosphorus pentoxide was proposed. The thiols obtained were used as starting materials for the synthesis of α-hydropolyfluoroalkanesulfenyl chlorides. The properties of the resulting F,S-containing compounds were studied.

Synthesis of low molecular weight thiols in response to Cd exposure in Thlaspi caerulescens

In this study, we investigated the accumulation of phytochelatins (PCs) and other low molecular weight (LMW) thiols in response to Cd exposure in two contrasting ecotypes differing in Cd accumulation. Using a root elongation test, we found that the highly accumulating ecotype Ganges was more tolerant to Cd than the low Cd-accumulation ecotype Prayon. L-buthionine-(S,R)-sulphoximine (BSO), a potent inhibitor of the gamma-glutamylcysteine synthetase gamma-ECS) (an enzyme involved in the PC biosynthetic pathway), increased the Cd sensitivity of Prayon, but had no effect on Ganges. Although PC accumulation increased in response to Cd exposure, no significant differences were observed between the two ecotypes. Cd exposure induced a dose-dependent accumulation of both Cys and a still unidentified LMW thiol in roots of both ecotypes. Root accumulation of Cys and this thiol was higher in Ganges than in Prayon; the ecotypic differences were more pronounced when the plants were treated with BSO. These findings suggest that PCs do not contribute to the Cd hypertolerance displayed by the Ganges ecotype of Thlaspi caerulescens, whereas Cys and other LMW thiols might be involved.

Synthesis, Structure, and Physicochemical Characteristics of Thiols

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Synthesis, Structure, and Physicochemical Characteristics of Thiols

Data on thiols structure, physicochemical characteristics, and synthetic procedures for preparation are systematized and generalized.

Trypanothione Synthesis in Crithidia Revisited

In Crithidia fasciculata the biosynthesis of trypanothione (N(1),N(8)-bis(glutathionyl)spermidine; reduced trypanothione), a redox mediator unique to and essential for pathogenic trypanosomatids, was assumed to be achieved by two distinct enzymes, glutathionylspermidine synthetase and trypanothione synthetase (TryS), and only the first one was adequately characterized. We here report that the TryS of C. fasciculata, like that of Trypanosoma species, catalyzes the entire synthesis of trypanothione, whereas its glutathionylspermidine synthetase appears to be specialized for Gsp synthesis. A gene (GenBanktrade mark accession number AY603101) implicated in reduced trypanothione synthesis of C. fasciculata was isolated from genomic DNA and expressed in Escherichia coli as His-tagged or Nus fusion proteins. The expression product proved to be a trypanothione synthetase (Cf-TryS) that also displayed a glutathionylspermidine synthetase, an amidase, and marginal ATPase activity. The dual specificity of the Cf-TryS preparations was not altered by removal of the tags. Steady-state kinetic analysis of Cf-TryS yielded a pattern that was compatible with a concerted substitution mechanism, wherein the enzyme forms a ternary complex with Mg(2+)-ATP and GSH to phosphorylate GSH and then ligates the glutathionyl residue to glutathionylspermidine. Limiting K(m) values for GSH, Mg(2+)-ATP, and glutathionylspermidine were 407, 222, and 480 microm, respectively, and the k(cat) was 8.7 s(-1) for the TryS reaction. Mutating Arg-553 or Arg-613 to Lys, Leu, Gln, or Glu resulted in marked reduction or abrogation (R553E) of activity. Limited proteolysis with factor Xa or trypsin resulted in cleavage at Arg-556 that was accompanied by loss of activity. The presence of substrates, in particular of ATP and GSH alone or in combination, delayed proteolysis of wild-type Cf-TryS and Cf-TryS R553Q but not in Cf-TryS R613Q, which suggests dynamic interactions of remote domains in substrate binding and catalysis.

Water Effects on SmI2 Reductions: A Novel Method for the Synthesis of Alkyl Thiols by SmI2‐Promoted Reductions of Sodium Alkyl Thiosulfates and Alkyl Thiocyanates.

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The synthesis of water soluble decalin-based thiols and S-nitrosothiols—model systems for studying the reactions of nitric oxide with protein thiols

The syntheses of three decalin-based tert-thiols displaying varying degrees of solubility in aqueous milieu are described. The S-nitroso derivatives of these compounds have also been prepared and the structures of two of these determined by single crystal X-ray diffraction. These compounds have been designed for studying the interaction of nitric oxide (NO) with thiols under physiological conditions.

Applications, Properties and Synthesis of ω-Functionalized n-Alkanethiols and Disulfides - the Building Blocks of Self-Assembled Monolayers

Self-assembled monolayers (SAMs) of alkane thiols on gold and other metals are versatile constructs with which to study interfacial phenomena and reactions at surfaces. Surface properties of SAMs - e.g., wettability, stability in diverse environments, propensity to interact with or to resist adsorption of macromolecules -- depend on and can be controlled flexibly by the properties of the functional (head) groups in the ω position of the alkyl chain. SAMs provide a basis for many important scientific and technological applications, ranging from micropatterning methods, through sensing, to biological recognition. Despite their importance, the literature on SAMs and the synthesis of molecules that constitute them remains scattered and often conflicting. The purpose of this Review is (i) to summarize the applications and physical properties of SAMs and (ii) to systematize the strategies of synthesis of ω-functionalized alkane thiols. Generic retrosynthetic scheme is developed that allows efficient synthetic planning. Issues related to the selection of appropriate protecting groups and the ways of introduction of the thiol functionality are discussed in detail, and illustrated with examples of syntheses of several complex alkane thiols.

Construction of C—S Bonds with a Quaternary Stereocenter Through a Formal Michael Reaction: Asymmetric Synthesis of Tertiary Thiols.

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Construction of C--S bonds with a quaternary stereocenter through a formal michael reaction: asymmetric synthesis of tertiary thiols.

Quaternary stereocenters that bear a sulfur substituent can be created with nearly perfect stereocontrol through an intramolecular Michael-type process. Lewis acids (L.A.) accelerate the intramolecular sulfur-atom transfer from the oxazolidine-2-thione functionality to the β carbon atom of the β,β-disubstituted enoyl moiety, whereas the chirality of the oxazolidine-2-thione portion controls reaction stereochemistry (see scheme).

Construction of CS Bonds with a Quaternary Stereocenter through a Formal Michael Reaction: Asymmetric Synthesis of Tertiary Thiols

Quartäre Stereozentren mit Schwefelsubstituenten entstehen annähernd stereospezifisch in einer Art intramolekularer Michael-Addition (siehe Schema). Lewis-Säuren (L.A.) beschleunigen die intramolekulare Übertragung des S-Atoms von der Oxazolidin-2-thion-Einheit auf das β-C-Atom der β,β-disubstituierten Enoylgruppe. Der chirale Heterocyclus bestimmt die Konfiguration des Produkts.

Thiol synthesis and arsenic hyperaccumulation in Pteris vittata (Chinese brake fern)

Pteris vittata (Chinese brake fern) has potential for phytoremediation of As-contaminated sites. In this study, the synthesis of total thiols and acid-soluble thiols in P. vittata was investigated under arsenic exposure. The strong and positive correlation between As concentration and acid-soluble thiols in plant leaflets suggests that acid-soluble thiols may play a role in As detoxification. A major As-induced thiol was purified and characterized. A molecular ion (M+1) of 540 m/ z suggests that the thiol was a phytochelatin (PC) with two base units (PC 2). However, the ratios of acid-soluble thiols to As in leaflets exposed to As ranged from 0.012 to 0.026, suggesting that only a very small part of As is complexed by PC 2. PCs could play a minor detoxification role in this hyperaccumulator. A PC-independent mechanism appears to be mainly involved in As tolerance, while PC-dependent detoxification seems to be a supplement.

Thiol synthesis and arsenic hyperaccumulation in Pteris vittata (Chinese brake fern)

Pteris vittata (Chinese brake fern) has potential for phytoremediation of As-contaminated sites. In this study, the synthesis of total thiols and acid-soluble thiols in P. vittata was investigated under arsenic exposure. The strong and positive correlation between As concentration and acid-soluble thiols in plant leaflets suggests that acid-soluble thiols may play a role in As detoxification. A major As-induced thiol was purified and characterized. A molecular ion (M+1) of 540 m/z suggests that the thiol was a phytochelatin (PC) with two base units (PC2). However, the ratios of acid-soluble thiols to As in leaflets exposed to As ranged from 0.012 to 0.026, suggesting that only a very small part of As is complexed by PC2. PCs could play a minor detoxification role in this hyperaccumulator. A PC-independent mechanism appears to be mainly involved in As tolerance, while PC-dependent detoxification seems to be a supplement.

Water Effects on SmI2 Reductions: A Novel Method for the Synthesis of Alkyl Thiols by SmI2‐Promoted Reductions of Sodium Alkyl Thiosulfates and Alkyl Thiocyanates

Water as a cosolvent has significant improving effect on the reductivity of SmI2 in the reduction of sodium alkyl thiosulfates and alkyl thiocyanates. A new method for synthesis of alkyl thiols by SmI2/THF/H2O system has been developed.