Cleavage photochemical oxidants

The use of AZ-hydroxypyridone salts ofrers some advantages over the procedures above in that the second step can be done under nonhydrolytic conditions either thermally or photochemically (equation 33). This could be advantageous for base sensitive substrates. However, these methods are unsuitable for aliphatic halides (alcohols are the major product), and there appear to be no a-halocatbonyl examples. For photochemical cleavage, the -oxides (1) and (2) offer some advantages. - However, the... 

These sites are passed to FEASIBLE-P, which searches the reaction-environment to establish potential radical forming processes thermal cleavage, photochemical cleavage, and oxidation-reduction processes. Attributes describing reaction-environment establish thermal cleavage as a likely initiation mechanism photochemical cleavage... 

Other alternatives for the oxidant for stoichiometric oxidations include the use of a selenoxide [99], including a photochemical oxidation of catalytic selenium [100], iodine [101], sodium chlorite [102], hypochlorite [103], and electrochemical methods [101,104]. Even air can be used as the oxidant [99,100], but care has to be taken with regard to the choice of solvent as cleavage of the product 1,2-diol can occur, especially when the alkene has an aryl substituent [53, 105, 106]. 

Depending on the chemical structure of the anchor and chemistry of its attachment to the resin, the product can be cleaved at the end of the synthesis either with acid, base or nucleophilic cleavage reagents, hydrogenolysis, enzymatic, palladium-catalyzed or photochemical, oxidative and reductive cleavage methods. In addition, the safety-catch anchors can be chemically modified at the end of the synthesis to provide a structure which is subsequently cleavable. 

Chemical or photochemical oxidation of a nucleic acid is accomplished very efficiently by a variety of metal complexes. In the presence of hydrogen peroxide and thiol, bis(phenanthroline) cuprous ion very efficiently cleaves DNA (26). Tris(phenanthroline) complexes of cobalt(IIl) or rhodium(III) promote redox reactions in their excited states (27, 28). These photoac-tivated probes bind to the DNA helix in a fashion comparable to the spectroscopic probes described above and then, upon photoactivation, promote DNA strand cleavage. 

Linear regression analysis showed that the production rates of DMS were closely correlated to DMSPd concentrations in the microlayer (i =0.5563, n=8, P=0.03) as well as in the subsm-face water (i =0.6220, n=8, P=0.02). The DMS production through enzymatic DMSP cleavage generally exceeded its microbial consumption rates, leading to net DMS production. The imbalance in these two processes might be caused by other sink pathways for DMS such as photochemical oxidation and sea-to-air emission. 

Adam, W., Arnold, M.A., Grimm, G.N., Saha-MoeUer, C.R., Dall Acqua, E, Miolo, G., and Vedaldi, D., 4-tert-Butylperoxyhnethyl-9-methoxypsoralen as intercalating photochemical alkoxyl-radical source for oxidative DNA cleavage, Photochem. PhotobioL, 68, 511, 1998. 

From what we know today about PET in biological and synthetic membrane or layered systems, we may expect that the non-biological apparatus providing photogeneration of spatially separated one-electron reductant and oxidant is likely to be developed in a rather universal way and may be expected to accomplish in the future not only water cleavage, but also various other redox reactions, such e.g., as photochemical synthesis of ammonia via the hv... 

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