Hydroxylation at an aliphatic carbon

C. Reactions Involving Replacement of Hydrogen by Heteroatoms 19-14 Hydroxylation at an Aliphatic Carbon Hydroxylation or Hydroxy-de-hydrogenation... 

Oxidation Carbon-Nitrogen Systems. Primary amines may be hydroxylated at the nitrogen atom (N-oxidation) to yield the corresponding hydroxylamine. Alternatively, primary alkyl or arylalkyl amines may undergo hydroxylation at the a-carbon to give a carbinolamine that decomposes to an aldehyde and ammonia (through the process of oxidative deamination). Secondary aliphatic amines may lose an alkyl group first N-dealkylation) prior to oxidative deamination. 

Alcohols and phenols contain the hydroxyl group (—O—H) as their functional group. Alcohols may be considered to be derived from saturated or unsaturated hydrocarbons by the replacement of at least one H atom by a hydroxyl group. The properties of alcohols result from a hydroxyl group attached to an aliphatic carbon atom, —C—O—H. Ethanol (ethyl alcohol) is the most common example (Figure 27-14). 

The sterols include that group of compounds which contain an alcoholic hydroxyl group at C3 and a branched aliphatic chain of at least eight carbon atoms at C17. These compounds, which include cholesterol and its derivatives, can occur as free alcohols or as long-chain fatty acid esters. A number of HPLC techniques have been used in the analysis of the sterols including reversed phase, non-aque-ous reversed phase, normal phase, argentation and combinations of the above. 

Aliphatic Oxidation and O-Dealkylation - Cytochrome P-450 monoxygenases appear to be involved in a variety of aliphatic hydroxylations. One common pathway involves an initial w-hydroxylation as with pentobarbital, followed by further metabolism to the aldehyde and acid by dehydrogenases. Hydroxylation also frequently occurs at the penultimate carbon as in amobarbital l, at benzylic and allylic positions and at carbons bearing a heteroatom. Many examples of such oxidations are cited in a recent review.Hydroxylation at carbon bearing a heteroatom such as oxygen, nitrogen or sulfur leads to the so-called dealkylation reactions so common in drug metabolism. 

One key aspect in the study of toxicity is the ability to predict the products of metabolism. In this respect P450s have been the major area of research for many years. The P450s have been shown to catalyze an almost bewildering number of reactions [6], In addition to the common hydroxylation reactions at aliphatic and aromatic carbon centers, they can directly oxidize heteroatoms... 

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