Hydroxylation and related reactions

Aldol addition and related reactions of enolates and enolate equivalents are the subject of the first part of Chapter 2. These reactions provide powerful methods for controlling the stereochemistry in reactions that form hydroxyl- and methyl-substituted structures, such as those found in many antibiotics. We will see how the choice of the nucleophile, the other reagents (such as Lewis acids), and adjustment of reaction conditions can be used to control stereochemistry. We discuss the role of open, cyclic, and chelated transition structures in determining stereochemistry, and will also see how chiral auxiliaries and chiral catalysts can control the enantiose-lectivity of these reactions. Intramolecular aldol reactions, including the Robinson annulation are discussed. Other reactions included in Chapter 2 include Mannich, carbon acylation, and olefination reactions. The reactivity of other carbon nucleophiles including phosphonium ylides, phosphonate carbanions, sulfone anions, sulfonium ylides, and sulfoxonium ylides are also considered. 

In addition to the direct absorption as a biological hazard, UV can have additional indirect effects on organisms.26,27 A number of UV photochemical reactions occur in solutions, both within cells and in the external aquatic environment. In the presence of UV, water itself is hydrolyzed, producing hydroxyl ions. Related reactions involving dissolved substances and mediated by UV lead to the formation of peroxides, super oxide, and other radicals. These reactive products are toxic by causing oxidative damage to biological molecules.28-31... 

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