Chemistry for pharmacy students general organic and natural product chemistry
The pharmacy profession and the role of pharmacists in the modern healthcare systems have evolved quite rapidly over the last couple of decades. The services that pharmacists provide are expanding with the introduction of supplementary prescribing, provision of health checks, patient counselling and many others. The main ethos of pharmacy profes-sion is now as much about keeping people healthy as treating them when they are not well. The modern pharmacy profession is shifting away from a product focus and towards a patient focus. To cope with these changes, and to meet the demand of the modern pharmacy profession, the pharmacy curriculum, especially in the developed world, has evolved signi?cantly. In the western countries, almost all registered pharmacists are employed by the community and hospital pharmacies. As a consequence, the practice, law, management, care, prescribing science and clinical aspects of pharmacy have become the main components of pharmacy curriculum. In order to incorporate all these changes, naturally, the fundamental science compo-nents, e.g. chemistry, statistics, pharmaceutical biology, microbiology, pharmacognosy and a few other topics, have been reduced remarkably. The impact of these recent changes is more innocuous in the area of pharmaceutical chemistry.
As all drugs are chemicals, and pharmacy is mainly about the study of various aspects of drugs, including manufacture, storage, actions and toxicities, metabolisms and managements, chemistry still plays a vital role in pharmacy education. However, the extent at which chemistry used to be taught a couple of decades ago has certainly changed signi?cantly. It has been recognized that while pharmacy students need a solid foundation in chemistry knowledge the extent cannot be the same as chemistry students may need.
There are several books on general, organic and natural product chemistry available today, but all of them are written in such a manner that the level is only suitable for undergraduate Chemistry students, not for Pharmacy undergraduates. Moreover, in most modern pharmacy curricula, general, organic and natural product chemistry is taught at the ?rst and second year undergraduate levels only. There are also a limited number of Pharmaceu-tical Chemistry books available to the students, but none of them can meet the demand of the recent changes in pharmacy courses in the developed countries. Therefore, there has been a pressing need for a chemistry text covering the fundamentals of general, organic and natural product chemistry written at a correct level for the Pharmacy undergraduates. Physical (Preformulation) and Analytical Chemistry (Pharmaceutical Analysis) are generally taught separately at year 2 and year 3 levels of any modern MPharm course, and there are a number of excellent and up-to-date texts available in these areas.
During our teaching careers, we have always struggled to ?nd an appropriate book that can offer general, organic and natural product chemistry at the right level for Pharmacy undergraduate students, and address the current changes in pharmacy curricula all over the world, at least in the UK. We have always ended up recommending several books, and also writing notes for the students. Therefore, we have decided to address this issue by compiling a chemistry book for Pharmacy students, which will cover general, organic and natural product chemistry in relation to drug molecules. Thus, the aims of our book are to provide the funda-mental knowledge and overview of all core topics related to general, organic and natural product chemistry currently taught in Pharmacy undergraduate courses in the UK, USA and various other developed countries, relate these topics to the better understanding of drug molecules and their development and meet the demand of the recent changes in pharmacy curricula. This book attempts to condense the essentials of general, organic and natural product chemistry into a manageable, affordable and student-friendly text, by concentrating purely on the basics of various topics without going into exhaustive detail or repetitive examples.
In Pharmacy undergraduate courses, especially in the UK, we get students of heterogeneous educational backgrounds; while some of them have very good chemistry background, the others have bare minimum or not at all. From our experience in teaching Pharmacy undergraduate students, we have been able to identify the appropriate level that is required for all these students to learn properly. While we recognise that learning styles and levels vary from student to student, we can still try to strike the balance in terms of the level and standard at a point, which is not too dif?cult or not too easy for any students, but will certainly be student friendly. Bearing this in mind, the contents of this book are organized and dealt with in a way that they are suitable for year 1 and year 2 levels of the pharmacy curriculum. While the theoretical aspects of various topics are covered adequately, much focus has been given to the applications of these theories in relation to drug molecules and their discovery and developments. Chapter 1 provides an overview of some general aspects of chemistry and their importance in modern life, with particular emphasis on medicinal applications, and brief discussions of various physical characteristics of drug molecules, e.g. pH, polarity and solubility. While Chapter 2 deals with the fundamentals of atomic structure and bonding, chapter 3 covers various aspects of stereochemistry. Chapter 4 incorporates organic functional groups, and various aspects of aliphatic, aromatic and heterocyclic chemistry, amino acids and nucleic acids and their pharmaceutical importance. Major organic reactions are covered adequately in Chapter 5, and various types of pharmaceutically important natural products are discussed in Chapter 6.
While the primary readership of this book is the Pharmacy undergraduate students (BPharm/MPharm), especially in their ?rst and second years of study, the readership could also extend to the students of various other subject areas within Food Sciences, Life Sciences and Health Sciences who are not becoming chemists yet need to know the fundamentals of chemistry for their courses.
Chemistry is the science of the composition, structure, properties and reactions of matter, especially of atomic and molecular systems.
Life itself is full of chemistry; i.e., life is the re?ection of a series of continuous biochemical processes. Right from the composition of the cell to the whole organism, the presence of chemistry is conspicuous. Human beings are constructed physically of chemicals, live in a plethora of chemicals and are dependent on chemicals for their quality of modern life. All living organisms are composed of numerous organic substances. Evolution of life begins from one single organic compound called a nucleotide. Nucleotides join together to form the building blocks of life. Our identities, heredities and continuation of generations are all governed by chemistry.
Atomic structure and bonding
The basic building block of all matter is called an atom. Atoms are a collection of various subatomic particles containing negatively charged electrons, positively charged protons and neutral particles called neutrons. Each element has its own unique number of protons, neutrons and electrons. Both protons and neutrons have mass, whereas the mass of electrons is negligible. Protons and neutrons exist at the centre of the atom in the nucleus.
Stereochemistry
Stereochemistry is the chemistry of molecules in three dimensions. A clear understanding of stereochemistry is crucial for the study of complex mole-cules that are biologically important, e.g. proteins, carbohydrates and nucleic acids, and also drug molecules, especially in relation to their behaviour and pharmacological actions. Before we go into further detail, let us have a look at different types of isomerism that may exist in organic molecules.
Organic functional groups
All organic compounds are grouped into classes based on characteristic features called functional groups.A functional group is an atom or a group of atoms within a molecule that serves as a site of chemical reactivity. Carbon combines with other atoms such as H, N, O, S and halogens to form functional groups. A reaction is the process by which one compound is transformed into a new compound. Thus, functional groups are important in chemical reactions. It is important that you are able to recognize these functional groups because they dictate the physical, chemical and other properties of organic molecules, including various drug molecules. The most important functional groups are shown in the following table, with the key structural elements and a simple example.
Organic reactions
A radical, often called a free radical, is a highly reactive and short lived species with an unpaired electron. Free radicals are electron-de?cient species, but usually uncharged. So their chemistry is very different from the chemistry of even-electron and electron-de?cient species, e.g. carbo-cations and carbenes. A radical behaves like an electrophile, as it requires only a single electron to complete its octet.
Radical reactions are often called chain reactions. All chain reactions have three steps: chain initiation, chain propagation and chain termination. For example, the halogenation of alkane is a free radical chain reaction.
Natural product chemistry
Natural products are products from various natural sources, plants, microbes and animals. Natural products can be an entire organism (e.g. a plant, an animal or a micro-organism), a part of an organism (e.g. leaves or ?owers of a plant, an isolated animal organ), an extract of an organism or part of an organism and an exudate, or pure compound (e.g. alkaloids, coumarins, ?avonoids, lignans, steroids and terpenoids) isolated from plants, animals or micro-organisms. However, in practice, the term natural product refers to secondary metabolites, small molecules (molecular weight < 1500 amu), produced by an organism, but not strictly necessary for the survival of the organism.
