Biological importance, functional groups

TABLE 1.2 Some biologically important functional groups... 

The hydrogen-bonded dimers with biologically interesting functional groups that have been studied by these methods are the OwH Ow bond in the water dimer and the OH -0=C bond in the formic and acetic acids dimers. They are important because they refer more directly to the intrinsic properties of a particular bond and provide experimental data for comparison with the ab-initio molecular orbital calculations on simple systems described in Chapter 4. 

The nitroaldol (Henry) reaction, first described in 1859, is a carbon-carbon bondforming reaction between an aldehyde or ketone and a nitroalkane, leading to a nitroalcohol adduct [29]. The nitroalcohol compounds, synthetically versatile functionalized structural motifs, can be transformed to many important functional groups, such as 1,2-amino alcohols and a-hydroxy carboxylic acids, common in chemical and biological structures [18, 20, 30, 31]. Because of their important structural transformations, new synthetic routes using transition metal catalysis and enzyme-catalyzed reactions have been developed to prepare enantiomerically pure nitroaldol adducts [32-34]. 

The most important functional groups with double bonds are the C=C of alkenes and the C=0 of aldehydes and ketones. Both appear in many organic and biological molecules. Their most common reaction type is addition. 

The chemistry of carboxylic acids is the central theme of this chapter. The importance of carboxylic acids is magnified when we realize that they are the parent compounds of a large group of derivatives that includes acyl chlorides, acid anhydrides, esters, and amides. Those classes of compounds will be discussed in Chapter 20. Together, this chapter and the next tell the story of some of the most fundamental structural types and functional group transfonnations in organic and biological chemistry. 

FIGURE 1.14 Some of the biologically important H bonds and functional groups that serve as H bond donors and acceptors. 

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