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- Herausgeber: Bentham Science Publishers
- Kategorie: Fachliteratur
- Serie: Medicinal Chemistry for Pharmacy Students
- Sprache: Englisch
The primary objective of this 4-volume book series is to educate PharmD students on the subject of medicinal chemistry. The book set serves as a reference guide to pharmacists on aspects of chemical basis of drug action. This first volume of the series is
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Seitenzahl: 459
Veröffentlichungsjahr: 2018
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Medicinal Chemistry for
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FOREWORD
For a pharmacist to be a successful member of the health care team, a foundation of medicinal chemistry knowledge is one of the essential elements to developing an adequate knowledge base, and critical thinking and problem solving skills. This e-book provides the fundamental principles of medicinal chemistry including the functional groups occurring in medicinal agents, the acidity and basicity of drugs, and their water and lipid solubility as well as drug-receptor interactions. The physicochemical principles, isosterism and spatial characteristics of drugs are prerequisites to understanding drug pharmacodynamics, pharmacokinetics, biopharmaceutics, formulations and pharmacotherapeutics. Another important aspect crucial to comprehending the mechanism of drug action is the knowledge of important biosynthetic pathways frequently encountered in the pharmaceutical interventions. A comprehensive approach has been taken to explaining the phases of drug metabolism, modifications of drug chemical structures and their effects on drug pharmacokinetics, safety and efficacy.
These authors have carefully integrated the key aspect of Doctor of Pharmacy curriculum in the design and organization of the contents in this eBook series; its novel and innovative layout includes 4 volumes in three distinct areas - the fundamental concepts, detailed structure activity relationships of different drug classes, and recent developments in the area of medicinal chemistry and drug discovery. It offers students the opportunity to learn the principles of drug action in a logical stepwise manner. The case studies, student’s self-study guide and self-assessments at the end of each chapter are unique features of this book that would be beneficial to both students, faculty members and clinicians. Although there are several medicinal chemistry textbooks available in the market, to my understanding, this is the first textbook of its kind focusing on the integration of medicinal chemistry into the foundations for a pharmacy curriculum.
As a pharmacy educator and pharmaceutical scientist, I am pleased to testify and endorse this e-book to the pharmacy educators, and learners as a novel and innovative addition to the available literature. One of the key advantages of this e-book is that it focuses its approach on a student-friendly manner that incorporates the appropriate illustrative diagrams and study guides as well as self-assessments to enable students to enhance their skills as self-learners. The increasing emphasis on clinical and management focuses in our pharmacy curriculum makes it challenging for students with limited time available to learn and internalize concepts in the area of medicinal chemistry. This e-book series brings those memories of my early years as a pharmacy student and the evolution of the pharmacy education, and gives me the confidence that it will pave the way of future medicinal chemistry education for pharmacists and other health professionals.
Preface
This is the first volume of the 4-volume eBook series, “Medicinal Chemistry for Pharmacy Students”. The primary objective of this e-Book series is to educate Pharm-D students in the area of medicinal chemistry and serve as a reference guide to pharmacists on the aspects of chemical basis of drug action. A thorough discussion of key physicochemical parameters of therapeutic agents and how they affect the biochemical, pharmacological, and pharmacokinetic processes and clinical use of these agents is the primary focus of the whole book. The rationale for putting together an e-Book of this nature is to equip Pharm-D students with the scientific basis to competently evaluate, recommend and counsel patients and health care professionals regarding the safe, appropriate, and cost-effective use of medications.
This first volume of the series titled, “Fundamentals of Medicinal Chemistry and Drug Metabolism”, is comprised of 8 chapters focusing on basic background information to build a firm knowledge base of medicinal chemistry. It takes a succinct and conceptual approach to introduce important fundamental chemical concepts, required for a clear understanding of various facets of pharmacotherapeutic agents, drug metabolism and important biosynthetic pathways that are relevant to drug action.
Chapter 1 is designed to ensure that the students learn about the scope and importance of medicinal chemistry, in addition to some important definitions. This chapter is an introduction to the overall role of a pharmacist and to the significance of medicinal chemistry in pharmacy education. It discusses the role of the pharmacist, history of medicinal chemistry and intellectual domains of medicinal chemistry.
Chapter 2 includes a comprehensive discussion of the four major biomolecules: proteins, carbohydrates, lipids, nucleic acids and key heterocyclic ring systems. Organic functional groups present in drugs, and biomolecules are reviewed in this chapter. Additionally, heterocycles present in drugs and biomolecules are reviewed in this chapter.
Chapter 3 focuses on acid base chemistry and salt formation; a brief review of the concepts of acid-base chemistry including the Arrhenius, Brønsted-Lowry, and Lewis concepts of acids and bases. It also highlights the significance of salt formation in pharmaceutical products, factors that determine ionization, and acid-base strengths. The application of acid-conjugate base, base-conjugate acid and Henderson-Hasselbalch equation in pharmacy and drug action and bioavailability are also discussed. The interpretation of pH partition theory, its significance in drug pharmacokinetics, the purpose of salt formation with drug molecules and the acidity or basicity of the salts are illustrated in this chapter.
Chapter 4 covers solubility and lipid-water partition coefficient (LWPC) concepts in detail with specific drug examples. Hydrophilicity, hydrophobicity and lipophilicity of drugs, and their effect on solubility are discussed to enable the readers to predict the water or lipid solubility of drugs based on their chemical composition. Additionally, the chapter includes a discussion of the effects of partition coefficient on drug bioavailability and action.
Chapter 5 reviews the concepts of isosterism, stereochemical principles, and their application. An explanation of drugs’ spatial factors, and their influence on drug action including definitions of important stereochemical parameters are also included.
Chapter 6 is a brief review of the mechanisms of drug action and discusses drug receptor interactions critical for pharmacological responses of drugs. This chapter also discusses the theories of drug action that include: occupancy theory, rate theory, induced-fit theory, macromolecular perturbation theory, and occupation-activation theory of “two-state” model.
Chapter 7 provides a detailed account of drug metabolism, prodrugs and related terminology. It provides a comprehensive account of the fundamental concepts of drug metabolism, describes the significance of drug metabolism, key enzymes involved in the sites of drug metabolism, phase I and phase II metabolic pathways that include oxidation reduction hydrolysis, glucuronic acid conjugation, sulfate conjugation, conjugations with glycine and other amino acids, glutathione or mercapturic acid, acetylation, and methylation. This chapter also defines and differentiates between prodrug, soft drug and antedrugs and discusses their clinical significance.
Chapter 8 provides a brief review of biosynthetic pathways frequently targeted by pharmaceutical interventions. The biosynthetic pathways discussed in this chapter include: eicosanoid biosynthesis (prostaglandins, prostacyclins and leukotrienes), epinephrine and norepinephrine biosynthesis, folic acid biosynthesis, steroid biosynthesis (cholesterol, adrenocorticoids and sex hormones) and nucleic acid biosynthesis (purines and pyrimidines anabolism, catabolism and salvages).
The chapters in this volume are designed to guide the reader to review, integrate and apply medicinal chemistry concepts to the study of therapeutic agents that are the focus of subsequent volumes. All concepts are illustrated with diagrams or figures, with the keywords highlighted, bulleted or numbered. Wherever needed, special boxes and case studies are included. In addition, each chapter is reinforced with practice problems and answer sets. Special notations are highlighted using call-out boxes for visual effect. Tables and figures are used to augment the text as needed.
We would like to express our sincere gratitude to the contributing authors for their time and effort in completing this volume. We would also like to thank Bentham Science Publishers, particularly Mr. Shehzad Naqvi (Senior Manager Publication), and Ms. Fariya Zulfiqar (Assistant Manager Publications) for their support. We are confident that this volume of the eBook series will guide students and educators of pharmacy and related health professions worldwide.
List of Contributors
Introduction
M. O. Faruk Khan1,*,Ashok Philip2Abstract
This chapter is an introduction to the overall role of pharmacist and the significance of medicinal chemistry in pharmacy education. After study of this chapter students will be able to:
• Discuss the role of the pharmacist • Highlight the history of medicinal chemistry • Illustrate the relevance of medicinal chemistry in pharmacy education • Recognize the significance of medicinal chemistry in pharmacy education • State important definitions in medicinal chemistry and pharmacy.
BRIEF HISTORY AND ROLE OF PHARMACISTS
Although the history of pharmacy goes back a long way, the profession of pharmacy emerged as a separate entity in America in the mid-19th century. In 1869, William Proctor Jr. defined pharmacy as the “art of preparing and dispensing medicine”, which “embodies the knowledge and skill requisite to carry them out to practice.” Philadelphia College of Pharmacy was the first to start the journey of institutional level pharmacy education in America in 1821 by establishing night school for apprentices and discussion groups for scientific pharmacy. The professional credentials for American pharmacists were strengthened with the initiation of the 4-year B.Sc. degree requirement for pharmacy licensure in 1932, which also gave the formal recognition of medicinal chemistry in academic pharmacy education [1, 2].
Since the beginning, both preparation and dispensing of medicine have been the scope of pharmacy practice; over decades, the role of a pharmacist has gradually shifted to a service and information provider and eventually to a patient care provider. Pharmacists are now required to provide counseling to Medicaid patients and to participate in drug utilization review programs. Soon after the Omnibus Budget Reconciliation Act of 1990 (OBRA 1990) was approved, all schools of pharmacy in America shifted to the 6-year (2 + 4) Pharm.D. program [1]. This trend has now continued to grow globally.
BRIEF HISTORY OF MEDICINAL CHEMISTRY
The origin of medicinal chemistry may be traced back to the early history of mankind when procedures such as refining sugar, fermenting wine, extracting vegetable oils, rendition of vegetable fats and saponification were known. The Chinese scholar-emperor Shen Nung, recommended the use of ch’ang shang for the treatment of malaria in 2735 B.C. The ancient Babylonian-Assyrian culture used 250 vegetable drugs and a few drugs from mineral and animal sources. Egyptian medicine, developed from a vegetable origin, was fully developed before 1600 B.C. Later in the 5th century B.C., Hippocrates recommended metallic salts for medical treatments and, together with Discarides, Pliny, and Galen, had a strong influence on Western medicinal chemistry. Materia Medica by Discarides discussed medicinal products at length. Galen introduced the term ‘Galenicals’ and Pliny translated the Greek medical symbols into Latin, thus making the knowledge of medicinal chemistry available to the scientific Western World [3].
The alchemists in the 13th century contributed a great deal to the development of medicinal chemistry. The Arabian medical treatises described senna, camphor, rhubarb, tamarind, and nutmeg as natural drugs. In 1240, German emperor Frederick II paved the way to assigning professional status for medicinal chemistry practitioners by issuing the Magna Charta of medicinal chemists. However, it was not until the Renaissance which gave birth to independent thought that further development in this young science was achieved [3]. Paracelsus, in the first half of the 16th century, challenged alchemy by announcing that the object of chemistry is not to make gold but to prepare medicine [4]. He believed that sickness is a disturbance of body chemistry and thus the preparation of medicine is an important job of the chemist – the basic tenet of today’s pharmaceutical chemistry was thus born [3].
Many drugs of plant origin emerged in South America, notably ginseng, mandrake, and wild licorice, about a century before North America started their search. The United States Pharmacopoeia and the National Formulary of North America in 1925 listed many more; Maya Indians alone had over 400 drugs.2 The isolation of benzoic acid in 17th century guided the principles of careful exami-nation of plant and animal products for their medicinal values and the isolation of ephedrine by Nagai in 1887 is a milestone of such investigation. Subsequent efforts were extended toward the synthesis of chemical constituents of plant and animal origins. Wohler was the first chemist to synthesize the organic compound urea and began the new science of synthetic organic medicinal chemistry as an important tool for the synthesis of modern drugs. The Kolbe synthesis of salicylic acid in the mid-19th century, Perkin synthesis of dyes in 1856, Dreser synthesis of aspirin in 1889 and barbital synthesis in 1903 by Fischer and Mering are a few milestones of discovering drugs by organic syntheses [5].
Ehrlich’s ‘side chain theory’ of drug action (1885) may be viewed as the starting point of modern medicinal chemistry [6], which led him in 1891 to coin the term ‘chemotherapy’. A chemotherapy is defined as “chemical entity exhibiting selective toxicities against particular infectious agent” [3]. Cambridge physiologist Langley (mid-1890s) supported the ‘side chain theory’, and described it in his publications as ‘receptive substances’. Today’s advancement of medicinal chemistry is largely indebted to this concept of receptors and its role in diverse biological processes [7]. A few key milestones concerning principles of drug action and modern medicinal chemistry are: Fischer’s (1894) lock-and-key theory, and Henry’s (1903) hypothesis on enzyme-substrate complex formation. Grimm’s and Erlenmeyer’s concepts of isosterism and bioisosterism (1929-1931) are also critical for understanding structure activity relationship (SAR, the relationship of chemical structure with biological activity) and drug discovery [5]. A few notable advancements in drug action and design in the mid to late 20th century include: (a) charge transfer concept of drug-receptor interaction (Kosower, 1955), (b) induced-fit theory of drug action (Koshland, 1958), (c) concepts of drug latentiation (Harper, 1959) and prodrug (Albert, 1960), (d) application of mathematical methods and transformation of SAR studies into quantitative SAR (QSAR) by Hansch and others (1960s), and (e) application of artificial intelligence to drug research by Chu (1974) [8].
Merrifield’s Nobel winning (1984) discovery of solid phase synthesis (1960s) led to the peptide synthesis on pin-shaped solid supports and discovery of combinatorial chemistry in 1984 by Geysen of Glaxo Wellcome Inc [9, 10]. The technique received widespread application by industries since the 1990s; the deconvolution of libraries (see latter in vocabulary section) and their intrinsic problems were addressed by Hougten and Frier (1993 and 1995) [11, 12]. In the mid-nineties Schultz et al. pioneered the discovery of luminescent materials by applying the combinatorial technique [13].
DEFINITION OF MEDICINAL CHEMISTRY
Medicinal chemistry is an interdependent mature science that combines applied (medicine) and basic (chemistry) sciences. It focuses the discovery, development, identification and interpretation of the mode of action of therapeutic agents at the molecular level. The clear understanding of chemical and pharmacological principles of drug molecules is dependent on detail SAR study, which is main emphasis of medicinal chemistry. Medicinal chemistry plays a major role in drug research and development by taking advantage of newer techniques and increased knowledge of different branches of related sciences including all branches of chemistry and biology [14].
MEDICINAL CHEMISTRY IN PHARMACY EDUCATION
The discipline of medicinal chemistry is devoted with the invention, discovery, design, identification and synthesis of biologically active compounds. Drug design and development and ADMET (absorption, distribution, metabolism, excretion, and toxicity) assessments are most relevant to pharmacy education and training. The interpretation of mode of action at the molecular level and construction of SAR of drugs and other therapeutic agents are important knowledge base for future pharmacists. Pharmacists are required to be competent in therapeutic decision making, which is dependent on their ability to conduct detail ADMET assessments of therapeutic drug classes. The pharmaceutical care and counseling to patient and other healthcare professionals are dependent on clinical pharmacists’ knowledge and training in therapeutic use of medications, evaluation of scientific literature, proper therapeutic evaluations of medications and development of evidence based patient-specific pharmacotherapy plans. They serve as primary resources for drug related facts and provide sound advice regarding the safe and cost-effective use of medications. Thus to become a competent pharmacist, the knowledge of the physicochemical principles, SAR, mechanism of action, pharmacology, toxicology and ADME of drugs are indispensable components of a professional Pharm.D. curriculum.
An Abridged Medicinal Chemistry Vocabulary [15]
The affinity of a drug is defined as its ability to bind to receptor, enzyme, or other biological target. Mathematically, it is the reciprocal of the equilibrium dissociation constant of the drug-receptor complex (KA), which is quantified by dividing the rate constant for offset (k-1) by the rate constant for onset (k1). Efficacy is the property by which drugs are able to elicit a response. Agonists may vary in the relative intensity of their response regardless of their affinity and number of the receptor sites they occupy. The maximal stimulatory response produced by a compound compared to that of a standard, or physiological agonist is defined as intrinsic activity (α). When the intrinsic activity of a compound is 1, it is categorized as full agonists, and when the value is zero, it is categorized as antagonists. Compounds with fractional values between 0-1 are known as partial agonists. A drug or an endogenous substance that interacts with a receptor to fully activate it and initiate a response is known as an agonist. An antagonist on the other hand opposes or blocks the physiological effects of the agonist by binding with the same receptor because of its lack of intrinsic activity. A partial agonist possessing fractional intrinsic activity for a particular receptor in a tissue is unable to produce maximal activation of that receptor regardless of dose. Potency of a drug is defined as the dose required to produce a specific intensity of response compared to a reference standard. A receptor is a polymer (macromolecule) present inside a cell or on the cell surface to specifically recognize and bind a drug molecule or any other compound acting as a molecular messenger to elicit a response. Biochemically it is a protein on the cell membrane or within the cytoplasm or the cell nucleus, and it binds to a physiological substrate such as a neurotransmitter, hormone, other substance, or a drug molecule to initiate the cellular response. Four kinds of regulatory proteins that serve as primary drug targets are: (i) enzymes, (ii) carrier molecules, (iii) ion channels, and (iv) receptors (‘true receptors’). There are still other structural proteins that may produce important pharmacological effects, e.g., tubulin is specific to colchicine, and drugs like taxoids bind to this colchicine binding site of tubulin to elicit the antineoplastic effects. When a messenger molecule (agonist) stimulates a specific receptor it may sometime increase or decrease another molecule or a metabolite or ion called a secondary messenger.Allosteric enzymes contain allosteric binding sites, which are separate from the substrate binding sites to which small molecules (other than substrate) may bind to enhance or reduce the effect of the enzymes by changing the conformation of the active site. Allosteric binding sites of enzymes and receptors may regulate (activate, or inhibit) the binding of the normal ligand by inducing conformational changes of the enzyme, or receptor – a process known as allosteric regulation.When a drug is structurally related to another drug with similar or different chemical and biological properties, it is known as an analog. A member of a series of compounds differing only in a repeating unit, such as a methylene group, or a peptide residue is termed homolog. A member of a series of compounds synthesized by similar chemical reactions and procedures are called the congeners (literally con- meaning with; generated meaning synthesized). Thus the term congener is often a synonym for homologue, but it is also frequently used interchangeably with the term analog in the literature.Combinatorial chemistry, or combinatorial synthesis is used to synthesize a combinatorial library (a large number of compounds) by combining sets of building blocks. High throughput screening (HTS) of the combinatorial library helps to discover lead compounds from a set of combinatorial libraries, which is a complex process. However, for ease of outcomes the deconvolution method is used. Deconvolution of libraries is a process of backtracking, reanalyzing, and resynthesizing the subset of structures of the combinatorial library showing promising activity in the preliminary HTS screening with the goal of tracking down the active principle(s).Drug targeting is a drug delivery strategy to a particular tissue of the body, which is often the desired site of action of the drug, to achieve drug selectivity and safety. Drug targeting can be performed by altering the drug structure to show increased selectivity for the target receptor. Not only it will produce the desired pharmacological response, but will also reduce adverse effects. Another strategy often used in drug targeting is site-specific delivery of drugs to its target tissue, using prodrugs or antibody recognition systems to reduce their systemic side effects and/or increase potency.Hansch analysis is a well-known technique that quantitates relationship of the physicochemical parameters, e.g., hydrophobic, electronic, steric and other characteristics, of a set of compounds with their pharmacodynamics and pharmacokinetic properties by using multiple regression analyses.Isosteres are molecules or ions containing the same number of atoms and valence electrons, e.g., O2-, F-, and Ne. Bioisosteres (or Non-classical isosteres) are compounds resulting from the exchange of atoms or of a group of atoms. Isosteric and bioisosteric replacements are often performed based on physicochemical or topological characteristics of the parent compounds to obtain a new drug with similar pharmacological activities.In the field of drug discovery, new compounds (the leads) with interesting biological activities and potential to become new therapeutic agents are routinely identified by a process called lead discovery. The strategy to identify such lead compounds is known as lead generation. The leads are further modified by a process called lead optimization to fulfill all stereological, electronic, physicochemical, pharmacokinetic and toxicological requirements to translate into clinically useful drugs.A pharmacophore is defined by the IUPAC as the “ensemble of steric and electronic features necessary to ensure the optimal supramolecular interactions with a specific biological target structure and to trigger (or to block) its biological response”. The concept of pharmacophore stems from the capacity of an imaginary group of compounds to interact with their receptor or an enzyme, at the molecular level. It does not necessarily represent a real molecule or a real association of functional groups, but is generally shared by a set of active molecules. The concept of pharmacophore is often mistakenly used to denote simple structural skeletons such as sulfonamides, flavones, phenothiazines, prostaglandins or steroids. Most useful drugs bind through the use of multiple weak bonds with the aid of H-bonding, hydrophobic and electrostatic interaction sites present in the atoms, rings, and centers, which are commonly defined as pharmacophoric descriptors.An inactive derivative of a drug that exerts pharmacological effects only after bioactivation is known as prodrug. When a prodrug is deliberately modified by the aid of a transient carrier group, which is often an easily hydrolyzable ester group, is known as carrier-linked prodrug. The purposes of such modification is to produce improved physicochemical or pharmacokinetic properties. There are also another group of prodrugs known as bioprecursor prodrugs that possess no such carrier and undergo one or more metabolic transformations in the body through normal metabolic pathway to their pharmacologically active forms. A soft drug is a compound that is metabolized quickly after exerting its therapeutic action in a predictable manner in vivo to produce inactive metabolites. An antedrug is an active derivative of a drug that is intended for local use which, upon entry into the systemic circulation, quickly undergoes metabolic inactivation and elimination. A hard drug is a metabolically stable, highly lipophilic compound that accumulates in adipose tissues and organelles or highly polar compound that is excreted easily through urine due to high water solubility. Pharmacologically, a powerful drug of abuse such as cocaine or heroin is commonly termed as a “hard drug”.Medicinal Chemistry in Drug Discovery and Development
Lomberdino and Lowe extensively reviewed the scope of medicinal chemistry in highly sophisticated process of drug discovery from a historical perspective [16]. Technological advances over the past few decades including computational chemistry and combinatorial chemistry have dramatically expanded the scope of medicinal chemistry in drug discovery. It is a long, complex, and costly process taking 12-24 years to launch a drug from bench to the market and costing up to US$ 1.4 billion for a single drug. It has been estimated that about 1 drug per 10,000 active principles in the bench come to the market and ~1 out of 15-25 clinical candidates survive the safety and efficacy standards to be marketable. Medicinal chemists play a crucial role in the early phases of drug discovery with the goal of maximizing efficacy and minimizing side effects. Their knowledge in modern organic chemistry and medicinal chemistry, biology of disease, in vitro and in vivo pharmacological screening and pharmacokinetic characteristics are the driving forces in a drug discovery project. The medicinal chemist is also well aware of ADMET issues related to medicines currently in the market for a target disease, regulatory affairs for similar drugs, current competitors in market, drugs in the pipeline, other related scientific matters in literatures, and technological advances. The study of drug design and discovery is an excellent source of knowledge base for pharmacists about drugs and diseases.
Medicinal Chemistry in Pharmacy Education
The sound knowledge of functional group chemistry of drug molecules, along with ADMET parameters, is fundamental to understanding routes of drug administration, selection of appropriate therapeutic agent and/or formulation, and the dosages [17]. Functional groups are critical to receptor binding, and thus influence the mode of drug action, determine drug potency and consequently their dosages. In this context, the ADMET intellectual domain of medicinal chemistry, especially the metabolism of drugs, is of value. Since metabolic reactions are dependent on the drugs’ electronic and steric characteristics of functional groups, one can effectively predict the potential drug metabolic outcomes from the knowledge of functional group chemistry and biochemistry.
Structurally based therapeutic evaluation (SBTE) is an innovative concept utilized by medicinal chemistry courses within pharmacy curriculum, developed by Alsharif et al. SBTE uses the knowledge of drug structures in making therapeutic decisions and emphasizes the relevance of medicinal chemistry to pharmaceutical care. All seven criteria of therapeutic decision making i.e. drug history/drug response, patient compliance, current medical history, past medical history, side effects, biopharmaceutics and pharmacodynamics are addressed in this SBTE approach. Students apply this newly designed SBTE approach to solve therapeutic problems for each class of drugs [18]. It has been described that the SBTE approach is valuable in guiding different functions of pharmaceutical care that include participating in drug selection decision process, patient counselling, monitoring patients to prevent drug interactions, selecting appropriate dosage forms and maximizing patient compliance by appropriate case stories. SBTE has also been shown to be of importance in developing professional practice skills like problem solving and decision making, learning from problem solving experiences, communicating, teaching, educating and collaborating [19]. Most importantly, using cardiovascular drugs as an example, SBTE has been shown to be a valuable tool for curriculum integration and interdisciplinary teaching [20-22].
The application of problem based learning (PBL) in medicinal chemistry teaching by some educators has shown to be valuable in pharmacy education. Medicinal chemistry based case studies were developed by integrating medicinal chemistry and pharmacology courses to solve clinical problems through group discussions [23]. Consequently, the overall outcome of clinical problem solving skills and the confidence of the students markedly improved, reiterating the significance of medicinal chemistry as a critical component of this pharmaceutical care directed learning [24, 25]. Roche and Zito developed computerized case studies emphasizing medicinal chemistry principles in the practice of pharmacy and evaluated the seven performance criteria with four of them showing positive results, specifically in: identifying relevant therapeutic problems, conducting thorough and mechanistic SAR analyses of the drug product choices provided, evaluating SAR findings in terms of patient needs and desired therapeutic outcomes, and solving patient related therapeutic problems [26, 27].
The design and discovery of drugs is the primary responsibility of a medicinal chemist, which is the source of pride to the pharmacist as the entrepreneur and innovator of the most important armor of health care, the medicine, and thus the leadership position in the healthcare sector. The subject areas that are fundamental to drug discovery also serve as the sources for a complete set of knowledge base of the diseases and their safe and economic treatments. By incorporating these into the pharmacy curriculum, pharmacists become invaluable to the healthcare community.
The uniqueness of the pharmacy profession primarily lies in the comprehensive expertise of medicines and other pharmaceutical products when compared to other healthcare professionals including doctors and nurses. Since medicines are primarily chemical entities, early histories of both pharmacy and medicinal chemistry overlap and are inherently bonded to each other. From the beginning of the academic pharmacy program in the United States, medicinal chemistry has been the indispensable component of its curriculum. Because of pharmacists’ unique knowledge of a medicine’s design, pharmacological action, manufacture, storage, use, supply and handling, they are in a suitable position in the health care sector. The legislative support (e.g. OBRA 1990) has increased the legal role of pharmacists in patient care; the product of which is today’s “Pharmaceutical Care”. Professionally, pharmacist cannot afford to ignore his or her identity as the medication safety expert if they want to successfully perform and hold on to this newly assigned additional responsibility on them. Thus, medicinal chemistry is an indispensable component for pharmacy profession. One cannot consider himself a pharmacist without a sound knowledge of all the components of medicinal chemistry. By embracing the discipline of medicinal chemistry, the pharmacy profession can reap manifold advantages.
SCOPE OF THIS BOOK SERIES
A drug is defined as any substance presented for treating, curing or preventing disease in human beings or in animals and can also be used for making a medical diagnosis or for restoring, correcting, or modifying physiological functions (e.g., the contraceptive pill). Chemically, a drug may be extremely complex or very simple. The study of medicinal chemistry and thus the scope of this book involves all about the drugs, simple or complex, that turns the mystery or fantasy regarding drugs’ behavior in the body into rationality. As medication experts, pharmacists routinely provide medication therapy evaluations and recommendations and counseling to patients and health care professionals. Clinical pharmacists are the primary resource for evidence-based information and advice regarding the safe, appropriate, and cost-effective use of medications. Thus, to become a competent pharmacist, the knowledge of chemical basis of drug action, its stability, pharmacology and toxicology are indispensable. The study of medicinal agents or drugs that are in clinical use, their metabolism, physicochemical principles, SAR, mechanism of action and toxicity are the scopes of professional pharmacy degree, which guide the breadth of this book.
This book is divided into four volumes:
Volume 1: Fundamentals of Medicinal Chemistry and Drug Metabolism.
Volume 2: Medicinal Chemistry of Drugs Affecting Autonomic and Central Nervous System.
Volume 3: Medicinal Chemistry of Drugs Acting on Cardiovascular and Endocrine Systems.
Volume 4: The Analgesic (Pain Management), Anti-infective, Anticancer and Other Agents and Recent Advances.
The first volume comprising of 8 chapters, focuses on basic background information to build a firm knowledge base of medicinal chemistry. It is a succinct and conceptual initial approach that introduces important fundamental chemical concepts required for a clear understanding of various facets of pharmacotherapeutic agents. The following volumes provide an in depth discussion of topics, including but not limited to: pharmacological and chemical basis of drug action, ADMET outcomes, drug-interactions, and adverse effects, which is expanded into different concepts and practical information on specific drug classes. A thorough discussion of key physicochemical parameters of therapeutic agents and how they affect the biochemical, pharmacological, pharmacokinetic processes and clinical uses of these agents are the primary focus of these volumes. The medicinal chemistry concepts of each drug class are illustrated by appropriate drug structures and relevant case studies. Drugs widely prescribed, both generic and brand names (Top 200), and those widely used in a hospital setting in the last four to five years have been selected as examples to reinforce the concepts. The last chapter of volume 4 will also cover topics related to advanced areas of medicinal chemistry such as drug discovery and development techniques. Overall, the goal of this book is to provide the Pharm. D. students with a comprehensive, student-friendly educational tool.
CONSENT FOR PUBLICATION
Not applicable.
CONFLICT OF INTEREST
This chapter is prepared based on an article published by the authors in American Journal of Pharmaceutical Education (Khan MOF, Deimling MJ, Philip A. Medicinal Chemistry and the Pharmacy Curriculum. Am J Pharm Educ 2011; 75(8): Article 161) with permission.
ACKNOWLEDGEMENT
None declared.
REFERENCES
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M. O. Faruk Khan1,*,Ashim Malhotra2Abstract
This chapter is a brief review of the important organic functional groups and biomolecules. After study of this chapter, students will be able to:
• Identify important organic functional groups in any drug structure • Identify major biomolecules: proteins, carbohydrates, lipids, nucleic acids • Apply chemical principles in all four classes of biomolecules • Define monomer units of the biomolecules and their chemical properties • Evaluate the structures of important heterocycles occurring in drugs and biomolecules • Summarize the significance of of biomolecules
AN INTRODUCTION TO ORGANIC FUNCTIONAL GROUPS
The reactivity of organic compounds stems from an atom or a group of atoms referred to as a functional group. Based on the characteristic features of the functional groups, organic compounds are classified into a large number of groups. The most important ones are: alkanes, alkenes, haloalkanes, aromatic hydrocarbons, alcohols and phenols, ethers and thioethers, aldehydes and ketones, amines, carboxylic acids and their derivatives, e.g., esters, amides, anhydrides, carbonates, carbamates, and ureas. Knowledge of functional groups is critical since they determine the physicochemical properties of organic compounds and drugs.
Alkanes, Alkenes and Cycloalkanes
Definition and Nomenclature of Alkanes, Alkenes and Cycloalkanes
Alkanes
The alkanes are hydrocarbons with the general molecular formula CnH2n+2. They are also referred to as saturated hydrocarbons (contain only single bonds), aliphatic or alicyclic (cyclic, but not aromatic) alkanes. This class of compounds possess tetrahedral atoms, which are sp3 hybridized. The common names of this family have a suffix ane and a prefix highlighting the number of carbon atoms, e.g., methane (1 carbon), ethane (2 carbons), propane (3 carbons), butane (4 carbons), pentane (5 carbons), hexane (6 carbons) and so on. However, as the compounds possess an increasing number of branched chains, resulting in multiple isomers, this system becomes less useful and the IUPAC (International Union of Pure and Applied Chemistry) nomenclature should be used.
Different compounds with the same molecular formula are referred to as isomers, which can be structural or conformational isomers. Two types of structural isomers exist, continuous chain and branched-chain isomers. For example, n-butane (a continuous chain structure) and isobutane (a branched chain structure) are structural isomers with the same molecular formula C4H10 (4 carbons), but different structures. As the carbon number increases, the number of isomers also increases dramatically. Thus, 75 isomeric alkanes are possible for 10 carbons and 366,319 isomers are possible with 20 carbons, thereby making IUPAC nomenclature more appropriate for use.
The general rule in the IUPAC system is to find the longest continuous chain alkane first, to assign the base name. The chain is then numbered in a way so that the substituents on the chain get the lowest possible number. For example, the IUPAC system of naming of one of the structural isomers of dodecane (12 carbons), 3,3-diethyl-2,5-dimethylhexane, is shown below.
In the example shown above with 3,3-diethyl-2,5-dimethylhexane, the carbon atoms with 3 hydrogen atoms (C-1 and C-6) are called primary carbons and the hydrogens attached to it are referred to as primary hydrogens. The carbon atoms with 2 hydrogen atoms (C-4) are referred to as secondary carbons and the hydrogens attached to it are referred to as secondary hydrogens. The carbon atoms with 1 hydrogen atom (C-2 and C-5) are referred to as tertiary carbons and the hydrogens attached to it are referred to as tertiary hydrogens. The carbon atoms with no hydrogen atom (C-3) are referred to as quaternary carbons.
Alkenes
Alkenes, also known as olefins, are unsaturated hydrocarbons containing carbon-carbon double bonds (also known as ethylenic double bond) with a general molecular formula CnH2n. Ethylene (C2H4
