Cysteamine, addition

FIGURE 10 Evaluation of antioxidative effects of cysteamine against high-molar-mass hyaluronan degradation in vitro induced by Weissbergers oxidative system. Reference sample (black) 1 mM Cull ions plus 100 pM ascorbic acid nil thiol concentration. Cysteamine addition at the onset of the reaction (a) and after 1 h (b) (25, 50,100 pM). (Hrabarova E, et al 2012). 

Another entry into the anti ulcer sweepstakes is etinfidine (50). It is synthesized by displacement of halide from 4-chloromethyl-5-methylimidazole (4 ) with substituted thiol The latter is itself made from thiourea analogue by an addition-elimination reaction with cysteamine 52. °... 

The chloroacetylurea derivative (A = C1CH2) obtained from the above addition (Eq. 1), on treatment first with thioacetic acid and Et3N and then with cysteamine, afforded the corresponding thiol (A = HSCH2) (Eq. 3)l5). 

Additional information <1> (<1> no inhibition by EDTA, GSH, cysteamine or high phosphate concentrations [1]) [1]... 

Grachev SA, Kropachev EV, Litvyakova Gl (1983) Synthesis of 5-S-cysteamine-6-hydroxythymine and evidence of its formation in the y radiolysis of aqueous solutions of thymine and cyste-amine. Bull Acad Sci USSR, Chem Ser (Engl Trans) 1595-1600 Grachev SA, Kropachev EV, Litvyakova Gl (1986) Addition of cysteamine to thymine and thymidine monophosphate initiated by y-irradiation. Bull Acad Sci USSR, Chem Ser (Engl Trans) 10 2178-2184... 

The types of compounds oxidized by FMOs are shown in Table 10.2 with some examples of reactions catalyzed shown in Figure 10.5. Substrates are soft nucleophiles and compounds containing additional charged groups (anionic or cationic) are excluded as substrates. With the exception of cysteamine, there are no known endogenous substrates. 

All of the above solutions were stirred for 30 min with a magnetic stirrer. The pH of the solutions was adjusted to 6 or 8 with 6N NaOH immediately after addition of cysteamine. The reaction mixtures were extracted with 70 ml of dichloromethane or chloroform for 6 h using a liquid-liquid continuous extractor. The extracts were dried over anhydrous sodium sulfate for 12 h. After the removal of sodium sulfate, 0.5 mg of N-methylacetamide was added to each solution as an internal standard. The extracts were quantitatively analyzed for thiazolidine and 2-acetylthaizolidine by GC. 

Effect of Derivatization pH on Aldehyde Recovery. Binding of aldehydes to other wine components (SOj, phenols, etc.) is highly pH dependent, therefore the effect of pH on derivatization efficiency was evaluated. Following addition of aqueous cysteamine to spiked wine samples, the pH was adjusted to 2, 8, or 10, and the solutions were allowed to react for 1 hour. The pH of all samples was then readjusted to 8.5, and the samples were extracted and analyzed as described above. Initial results indicated that no consistent differences in recovery at the different pH s were observed, however, overall variability appeared greater at pH 2. These results provide preliminary evidence that the total aldehyde concentration (free plus bound) is measured with this procedure. Further studies with model solutions containing added SO2 and phenols are needed to fully evaluate this result. 

Addition and elimination reactions of RS radicals derived from cysteamine and 2-mercaptoethanol involving C5-C6 double bond in various pyrimidines (thymine, uracil, and cytosine) were studied by the pulse radiolysis technique in aqueous solutions.For this purpose the kinetic parameters, i.e. the rate constants of the addition and elimination reactions, were determined using two chemical-monitoring systems. 

Pantothenic acid is of ubiquitous occurrence in nature, where it is synthesized by most microorganisms and plants fi-om pantoic acid (D-2,4-dihydroxy-3,3-dimethylbutyric acid) derived from L-vafine, and p-alanine derived from L-aspartate. Addition of cysteamine at the C-terminal end and phosphorylation at C4 of pantoic acid forms 4 -phosphopantetheine, which serves as a covalently attached prosthetic group of acyl carrier proteins, and, when attached... 

With heating in the presence of aqueous HCl, alcohols add to the triple bond of phosphonylated nitriles to produce the corresponding iunidcs. - Several variations on the preparation of diethyl l-(thioacetamido)methylphosphonate by mercaptolysis of diethyl cyanomethylphosphonate have been reported. Best yields, up to 90%, are obtained by addition of H2S to a suspension of diethyl cyanomethylphosphonate, EtjN, and tetrabutylphosphonium bromide in toluene (Scheme 6.59). The early reported procedure using mercaptolysis at room temperature of a mixture of diethyl cyanomethylphosphonate, EtjN, and Py led to diethyl l-(thioacetamido)methylphosphonate in low to good yields (23-85%). The addition of cysteamine to the cyano group has also been reported. ... 

Our team also realized the synthesis of macromonomers with a polymerizable double bond by using peculiar transfer agents. For instance, telomeriza-tions of (meth)acrylates were performed in the presence of cysteamine, i.e., thiol with an amine group, leading to PMMAs with an amine at the chain end [253]. However, amines enable the Michael addition onto the double bond activated by the carbonyl group. Hence, before performing the telom-erization, the amine group is protected (chlorhydrate salt) and recovered by a simple basification of the solution (Scheme 48). 

This result suggests that the addition of a reductant would reduce the radiation effect which is also observed. For example, 20 Gy is required to kill 80% of a cell population in the presence of cysteine (or cysteamine), while in the referraice system without cysteine the same effect is caused by only S Gy. Cysteine is oxidized to cystine. 

In this section we examine structurally complex thiazines, where the heterocycle forms part of a polycyclic system. Many of these fascinating natural products also contain quinone chromophores, and in many cases the corresponding compound lacking the thiazine ring also occurs in Nature. Hence it appears that the thiazine ring is added late in the biosynthetic pathway, presumably by addition of cysteine, cysteamine or hypotaurine to the quinone. 

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