Salicylate esters, functional groups

Certain functional groups in drug molecules are prone to chemical degradation. Drugs with an ester functional group are easily hydrolysed e.g., aspirin is easily hydrolysed to salicylic acid. Similarly, many drug molecules are susceptible to oxidation because of certain oxidizable functional groups, e.g. alcohol. 

In this reaction, the hydroxyl group (—OH) on the benzene ring in salicylic acid reacts with acetic anhydride to form an ester functional group. Thus, the formation of acetylsalicylic acid is referred to as an esterification reaction. This reaction requires the presence of an acid catalyst, indicated by the above the equilibrium... 

At a finer level of resolution, compounds with similar hydrocarbon skeletons may vary in functional group, degree of unsaturation, or oxidative state. For example, the volatile methyl esters of benzoic, salicylic and anthranilic acids (1 Fig. 5.1) differ only in -position functionality, but they are olfactorily distinct to humans and at least to some phytophagous insects (Raguso et al, 1996 Maekawa et al., 1999). Furthermore, many scent compounds have positional isomers and enantiomers that elicit different behavioral responses from flower visitors (Williams and Whitten, 1983 Hick et al, 1999). The refinement of capillary gas chromatography-mass... 

Esters are generally safe to use, with low toxicity (see exception of methyl salicylate and sabinyl acetate found in Spanish sage). Although few essential oils have esters as their main components, esters are found in greater numbers than other functional groups. 

Since salicylic acid has both an alcohol functional group and a carboxylic acid functional group, it can undergo two different esterification reactions depending on which functional group reacts. For example, when treated with ethanoic acid (acetic acid), salicylic acid behaves as an alcohol and the ester produced is acetylsalicylic acid (aspirin). On the other hand, when reacted with methanol, salicylic acid behaves as an acid and the ester methyl salicylate (oil of wintergreen) is produced. Methyl salicylate is also an analgesic and part of the formulation of many liniments for sore muscles. What are the structures of acetylsalicylic acid and methyl salicylate ... 

Hydrolysis is a major biotransformation pathway for drugs containing an ester functionality. This is because of the relative case of hydrolyzing the ester linkage. A classic example of ester hydrolysis is the metabolic conversion of aspirin (acetylsalicylic acid) to salicylic acid. " Of the two aslcr moieties present in cocaine, it appears that, in general, the methyl group is hydrolyzed preferentially to yield ben-roylecgoninc os the major human urinary metabolite. The... 

Prepare a 1M solution of hydroxylamine in coupling buffer sufficient to again treat the slide. The pH of the coupling buffer should be adjusted to pH 10 after dissolving the hydroxylamine into it. Expose the slide to the hydroxylamine solution in the same manner as the crosslinker treatment. The hydroxylamine will react with the methyl ester groups on the salicylic acids and form hydroxamate functionalities suitable for conjugation with the P(D)BA-modified protein from above. 

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