Salicylic acid discovery

Traditionally, lead compounds have been discovered in one of two ways. The hrst is one of trial and error. This is the way many plant and animal products and minerals have been found to be effective in the treatment of some medical disorder. For example, no one knows when the hrst person learned that chewing on the bark of the willow tree [Salix alba) helped relieve pain and reduce fever, but willow bark has been used in many cultures for untold centuries for just that purpose. Today we know that the active ingredient in willow bark is a derivative of salicylic acid (CgH4(OH)COOH), which today is sold commercially as aspirin or one of its analogs. Drug researchers continue to rely heavily on the study of folk medicines—a science known as ethnopharmacology—for the discovery of new plant and animal products that may have medical applications in the modern world. Indeed, scientists have discovered that the medical... 

Stadeler s discovery of the formation of chloranil from tyrosine led to the supposition that tyrosine was a derivative of salicylic acid, and on this assumption Schmidt and Nasse attempted to synthesise tyrosine from ethylamine and iodosalicylic acid, and from amidosalicylic and ethyl iodide, but did not succeed. On heating tyrosine they obtained a base CgHuNO, which they thought analogous to the one Schmidt had obtained by heating amidosalicylic acid on this account they held to the accuracy of the theory that tyrosine was ethylamidosalicylic acid. 

In 1831 and 1832 Soubeiran, Guthrie and Liebig independently reported the discovery of chloroform and in 1852 Gerland published on the synthesis of salicylic acid - these activities heralding the midcentury beginnings of the use of anaesthetics and the synthesis of new agents of therapy. 

The discovery of aspirin or acetylsali-cylic acid as a pain reliever is credited to Felix Hoffman (1868-1946) who was looking for a substitute for sodium salicylate to treat his father s arthritis. Hoffman uncovered and continued the work of Gerhardt from forty years before. Hoffman reacted salicylic acid with acetic acid to produce acetylsalicylic acid in 1897 Figure 13.3. 

A history of ether and etherification is a welcome, and now rare, focus on an individual compound.72 It covers work by Berzelius, Gerhardt, Hennell, Kolbe, Liebig, and of course Williamson. Acetoacetic ester has received detailed historical notice in a biography,73 as have salicylic acid and the salicylates.74 Apart from natural products, few heterocyclic substances have been recently the subject of historical enquiry. An impressive exception is that of pyrrole, a simple molecule explored by Dippel, Reichenbach, Runge and others, and manufactured by Du Pont.75 There is also an account of the structural problems posed by piperidine.76 Accounts have been given of the discovery of aniline from crystallin (a product of the thermal decomposition of indigo),77 of the history of phenol over the last two centuries,78 and of organic nitrates and their uses in medicine.79... 

From a synthetic standpoint, a historical landmark, after the discovery of electrophilic substitution in the 1860 s, was the synthesis of aspirin, acetylsalicylic acid. The earliest known use of the drug can be traced back to the Greek physician Hippocrates in the 5 century BC. He used powder extracted from the bark of willow trees to treat pain and reduce fever. Sali-cin, the parent of the salicylate drug family that generates salicylic acid in vivo, was isolated... 

That the discovery of the patentee was a most valuable one clearly appears. Even a small amount of free salicylic acid injures the stomach but, if this can be taken out, the acid is not dissolved in the stomach and does not injure it, but is held in bond intact until it reaches the lower digestive tract. While the discoveries of Von Gilm, Kraut, and others were known for many years before 1898, yet no extensive practical use was ever made of them, while the patented product went into immediate use and so continues on a large scale. 

Derivative benzoates and parabenzoates have been used primarily in fruit juices, chocolate syrup, pie fillings, pickled vegetables, relishes, horseradish, and cheese (Barbosa-Canovas et al., 2003). Other foodstuffs where sodium benzoate is used include soft drinks, baked goods, and lollipops (Poulter, 2007). Benzaldehyde and benzoic alcohol are better known to be yeast inhibitors. Benzoic acid has been found to release fewer protons than sulphite, nitrite, or acetic acid and it may be speculated that benzoic acid is not a classic weak-acid preservative. However, due to a lower pKa value, benzoic acid releases three to four times more protons than sorbic acid. This is a sizable concentration of protons although not as much as other weak-acid preservatives (Stratford and Anslow, 1998). Inhibition of growth is strongly pH-dependent and most effective under acidic conditions. Under these conditions the protonated form of the acid is predominantly found (Visti, Viljakainen, and Laakso, 2003). Another unexpected discovery was that benzoic acid appears to be a pro-oxidant. This was unexpected as it is a well-known fact 2-hydroxybenzoic acid (or salicylic acid) acts as a scavenger of free radicals in vivo (Piper, 1999). 

Ortho" (Greek for regular or right) often designated the first or best-known isomer such as salicylic acid for the hydroxybenzoic acidS or orthophosphoric acid. "Para" (Greek for alongside) was conventionally used upon the discovery of any additional isomer and the Zaitsev/... 

Fischer isomer of salicylic acid received this designation (paraoxybenzoic acid) upon its discovery in 1863. "Meta" (Greek for after) remained as an alternate designation for additional isomers, cf. metaphosphoric acid. The hydroxybenzoic acid model eventually and indirectly became the reason why in modern terms "ortho" indicates 1,2 placement (as for salicylic acid), "para" the 1,4 isomer (as for paraoxybenzoic acid), and "meta" the remaining option, namely, 1,3. 

Since their discovery during the 1860s, electrophilic aromatic substitution reactions played the dominant role for functionalizations of arenes, and were often the method of choice for the synthesis of substituted arenes. For example, Hermann Kolbe, a student of Friedrich Wohler, devised a synthesis for salicylic acid (7) [13, 14], which set the stage for the industrial preparation of acetylsalicylic acid (ASA, aspirin) (1) by Arthur Eichengriin and Felix Hoffmann at Bayer in 1897 (Scheme 1.2). 

The use of semi-synthetic derivatives as drugs developed from plant natural product lead compoimds began at the end of the nineteenth century and may be exemplified by drugs like aspirin (acetyl salicylic acid). From then on, the potential of plant-derived compounds as leads in drug discovery has been realized on numerous occasions [8], A survey released recently revealed that over 40% of the new small-molecular single chemical entity drugs introduced to the market from 1981 to 2006 are natural product derivatives, with 28% of them being chemical semi-synthetic modifications... 

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