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From Organic Molecules to Medicines. Chapter 14 – Heinemann Chemistry 2. From Organic Molecules to Medicines. One very useful application of organic reaction pathways is in the design and synthesis of medicines. The main ingredients of medicines are drugs .
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From Organic Molecules to Medicines Chapter 14 – Heinemann Chemistry 2
From Organic Molecules to Medicines • One very useful application of organic reaction pathways is in the design and synthesis of medicines. • The main ingredients of medicines are drugs. • A drug is any substance that alters a chemical process in the body.
Aspirin • Aspirin is widely used as a painkiller (analgesic) and relieve inflammation and fever. • It has its origins from a naturally occurring substance called salicin. • Salicin is converted to salicylic acid in the body and this is the active substance that fights pain. • Salicylic acid proved to be a more effective pain killer than salicin but the acidic nature gave it an unpleasant taste and caused mouth and stomach irritations.
Aspirin • It was found that the hydroxy group on the salicyclic acid molecule will react with ethanoic acid to form an ester called acetylsalicylic acid. • The ester was much less irritating to the stomach and was tasteless compared to taking salicylic acid by itself. • The ester is then hydrolysed in the alkaline conditions in the small intestine and the salicylic acid can take effect.
Organic Pathway to Aspirin • Acetylsalicylic acid can be formed by a direct condensation reaction between salycylic acid and ethanoic acid but the reaction is slow and the yield is low. • A more effective pathway is to form the ester from salicylic acid and ethanoic anhydride.
Penicillin • Penicillin was discovered by accident when scientist Alexander Fleming found a mould growing on a petri dish containing a culture of staphylococcus bacteria. • He found that the mould was killing the outer edges of the bacteria. • A few years later, an Australian scientist named Howard Florey improved processes to extract larger amounts of penicillin from this mould and used it for its antibiotic effects.
Penicillin Figure 14.11Fleming’s culture plate. The mould on the left (Penicillium notatum) is overcoming the growth of the smaller staphylococci.
Penicillin • As bacteria can reproduce every half an hour, it has the ability to evolve much faster than humans. As such, it is able to build up a resistance penicillin. • To combat this, scientists synthesised different strains of penicillin with different side chains. • They also synthesised penicillin that could be taken orally instead of being injetced.
Penicillin Figure 14.12The molecular structures of penicillins F, G, and V. The structures were worked out by Dorothy Hodgkin (Figure 12.29), who also worked out the structures of insulin and vitamin B12.
Penicillin Figure 14.13The structure of6-aminopenicillanicacid. Figure 14.14Structure of oxacillin.
Greener Production of Medicines • When chemists first developed synthetic pathways for making useful drugs, their main concern was to get a good yield. • Some methods contained a large amount of steps and as such produced a large amount of waste products. • This is referred to as poor atom economy.
Greener Production of Medicines • Over time, chemists have worked out greener reaction pathways that are more efficient in terms of using fewer steps in the synthesis, greater yields and better atom utilization. • This has made large savings both in dollar terms and environmental impact.
