Protection reactions

Normally, a layer of FeS scale, produced in the first reaction, protects the interior of the pipe or vessel. However, in the second reaction, cyanide removes the FeS protective scale exposing more free iron to react with H2S and releasing more hydrogen. Without protection, this cycle continues until blistering, cracking, and eventual total corrosion of equipment occurs. 

Ascorbate has multiple antioxidant capacities and may be the most important water-soluble defence against free-radical damage in human plasma. At millimolar concentrations, ascorbate scavenges O2, OH and HOCl (Blake et al., 1983). The latter reaction protects plasma lipids against degradation by activated PMNs. 

For this purpose, perfluorooctanesulfonyl-tagged benzaldehydes were reacted with 1.1 equivalents of a 2-aminopyridine (or 2-aminopyrazine), 1.2 equivalents of an isonitrile, and a catalytic amount of scandium(III) triflate [Sc(OTf)3] under micro-wave irradiation in a mixture of dichloromethane and methanol (Scheme 7.85). A ramp time of 2 min was employed to achieve the pre-set temperature, and then the reaction mixture was maintained at the final temperature for a further 10 min. The fluorous tag constitutes a multifunctional tool in this reaction, protecting the phenol in the condensation step, being the phase tag for purification, and serving as an acti-... 

The data presented in this chapter are from experiments with the fluorescein-conjugated A -formyl peptide (A -formyl-Met-Leu-Phe-Lys FMLPK-Fl), which we prepared with the reagents and reactions protected from the light as much as possible as described below. 

These reactions protect the body from the accumulation of many compounds but in some cases can cause serious problems. The best known of these involves acetaminophen. Its oxidation by cytochrome P450 2E1 or by prostaglandin H synthased yields a... 

Type of reaction protection Reaction condition solid-state... 

In order to avoid tedious separation of the isomers and to increase the scale of the reaction, protected alkynes were used. 2-Ethynyl-5-trimethyl-silylthiophene was used. The irradiation of 5-iodothiophene-2-carbalde-hyde in the presence of this compound gave only the expected substitution... 

Acrolein forms adducts with thiols such as glutathione, cysteine, N- acetylcysteine, and others. Such reaction protects tissues and cells from the cytotoxic effects of acrolein or acrolein-releasing substances (Brock et al. 1981 Chaviano et al. 1985 Dawson et al. 1984 Gurtoo et al. 1983 Ohno and Ormstad 1985 Whitehouse and Beck 1975). 

Methods in Organic Synthesis—33,000 reactions, Protecting Groups—functional group protection with region/stereoselectiv-ity... 

The body s - and the skin s - enzyme reactions are pH-sensitive. It is vital for the body to keep the pH of an organ stable in order to stabilize enzyme reactions. Protection against pH variations-the buffer capacity-must be extremely active and strong, as natural metabolic processes permanently synthesize acids and alkalis that are liable to modify the pH. 

T pe of reaction protection Reaction condition solvent-free Keywords aldehyde, ethane-1,2-diol, acetalization, acetal... 

---