Introduction
By natural products, we mean the molecules of nature. Of course, all life is made of molecules, and we will not be discussing in great detail the major biological molecules, such as proteins and nucleic acids, which we looked at in Chapters 49 and 50. In this chapter we shall talk much more about molecules such as adrenaline (epinephrine). Adrenaline is a human hormone. It is produced in moments of stress and increases our blood pressure and heart rate ready for ‘fight or flight’. You’ve got to sit an exam tomorrow—surge of adrenaline. To an organic chemist adrenaline is intensely interesting because of its remarkable biological activity—but it is also a molecule whose chemical reactions can be studied, whose NMR spectrum can be analysed, which can be synthesized, and which can be imitated in the search for new medicines. By the end of this chapter we hope you will be able to recognize some basic classes of natural products and know a bit about their chemistry. We will meet alkaloids such as coniine, the molecule in hemlock that killed Socrates, and terpenes such as thujone, which was probably the toxin in absinthe that killed the nineteenth-century artists in Paris. Then there are the ambiguous natural products such as the steroid cholesterol, which may cause innumerable deaths through heart disease but which is a vital component of cell walls, and the polyketide thromboxane, one drop of which would instantaneously clot all the blood in your body but without which you would bleed to death if you cut yourself.