Para-amino salicylic acid

Figure 8.17 Diazotized para amino salicylic acid conjugated to HDI meant for releasing the drug in the colon, by specific cleavage of the diazo hnkage by gut bacteria.

Figure 1. Examples of compounds in three different classes of non-steroidal antiinflammatory drags (NSAIDs) A. Salicylates salicylic acid and acetyl-salicylic acid (ASA, trademarks Aspirin, Bufferin, Alka-Seltzer) B. Para-amino phenols acetaminophen (trademark Tylenol) C. Non-salicylate aspirin-like drags ibuprofen (trademarks Advil, Motrin, Nuprin)...

Salicylic acid is orthohydroxybenzoic acid. Metahydroxybenzoic acid was discovered by B. W. Gerland by the action of nitrous acid on meta-amino-benzoic acid, parahydroxybenzoic acid by C. Saytzeff by heating anisic acid (methylparahydroxybenzoic acid) with hydriodic acid — a precursor of Zeisel s method (see p. 871), and G. Fischer from para-aminobenzoic acid, which he discovered by the action of ammonium sulphide on paranitrobenzoic acid. Kolbe obtained the para-compound by passing carbon dioxide over potassium phenoxide at i7o°-2io° (sodium phenoxide gives only a small yield). 

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