Thiols precursors

A non-thiol precursor, a solid lead chloride-octanoate complex, produces mendi-pite nanobelts after being heated in air for 1 h at 190 °C (Fig. 20.4). A remark-... 

Table 10.1 Survey of molecules investigated at different junctions N = number of molecules / = tunneling decay parameter R = resistance compound numbers in parentheses refer to protected thiol precursors.

Universal thiol precursor (X—SH) of oxidation products Cysteine sulphinic acid (X—SCFH), Cysteic acid (X-SO-jH) Cystine (X-S-S-X) ... 

Spinacia oleracea (Chenopodicaeae) animals thiol precursor (HC-SH) of oxidation products Homocysteine sulphinic acid (HC-SO9H) Homocvsteic acid (HCASO3H)... 

Methods to measure cysteinylated aroma precursors in must were developed by Peyrot des Gachons et al. (2000) and Murat et al. (2001b). They allowed the location of thiol precursors to be determined in Sauvignon blanc grapes (Fig. 8B.7). Around 80% of P-4MSP is in the juice and 50% of P-3SH in the skin. The skin contact improves the must aromatic potential, but its main effect is on the P-3SH content (Fig. 8B.8). Similarly, in Cabernet Sauvignon and Merlot grapes, 60% of the P-3SH is located in the skins This method has been also applied to study the influence of... 

The equivalent material based on the larger pore SBA-15 silica molecular sieve was prepared as follows. Pluronic 123 (EO20PO70EO20, Mav 5800, Aldrich) (4 g) was dissolved with stirring in 125 g of 1.9 M HCl solution at room temperature. The solution was heated to 40 °C before adding 32.8 mmol TEOS. After 1 hour, 8.2 mmol thiol precursor MPTS was added to the mixture. The resultant solution was stirred for 20 hours at 40 °C, and then aged at 100 °C for 24 hours without stirring. The solid product was recovered by filtration and air-dried. The template was extracted with excess ethanol under reflux for 24 hours (1.5 g of as-synthesized material per 400 ml of ethanol). ... 

In conclusion, the oxidation of free thiol precursors remains the method of choice for preparing multiple disulfide peptides, in particular the synthetic versions of natural structures. It requires only one type of protecting group for Cys and allows Cys pairing under mild conditions that often favor nativelike folding. 

Table 1 Recent Examples of Multiple Disulfide Peptides Prepared from Free Thiol Precursors... 

Figure 6. Average nanocrystal diameter (%) and size distribution moments, p (A) and // ( W), of perfluorodecanethiol-coated silver nanoaystals synthesized at 80 C with a precursor concentration of 3.5 mM and thiol precursor ratio of 2.5 as a function of solvent pressure. The error bars represent the standard deviation of the samples. (Reproduced from reference 19.

These assay methods have made it possible to determine the location of cysteinylated thiol precursors in Sauvignon Blanc grapes (Figure 7.12). The 4-MMP and 4-MMPOH precursors are mainly located in the flesh (approximately 80%), while the skin and flesh contain equal amounts of 3-MH precursor (Peyrot des Gachons et al., 2002a). Similarly, a majority (60%) of the 3-mercaptohexan-... 

Pena-GaUego, A., Flemandez-Orte, P., Cacho, J., Ferreira, V. (2012). 5-cysteinylated and S-glutathionylated thiol precursors in grapes - a review. Food Chemistry, 131,1-13. 

Amino-2-arylazo-2-butenoic acids (289) have been prepared by two pathways from acetoacetic esters. The reaction of these compounds with bligomeric a-mercapto-aldehydes leads to substituted thiazoleacetic esters (290), which appear to be useful intermediates for the synthesis of penicillin analogues. Most syntheses of 2,4-dioxa-l,3-thiazolidines (292), which show an interesting spectrum of biological activity, involve oxidation of thiol precursors. A new method uses readily available dihydropyrimidine thiones in reaction with chloro-acetic acid. The reaction does not proceed if R = H in (291). 

Scheme 1 y-Thiolactone entity as a reactive thiol precursor the thiol is released by aminolysis and a subsequent thiol-click occurs, incorporating Ri and R2 residues... 

Radical-induced cyclizations have been used to prepare thiolans of the type (16), the unsaturated thiol precursors being prepared by the reaction of allyl-... 

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