Module Objectives: Why to study Organic Pharmaceutical Chemistry? 24-Oct-17

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2 2 Useful Info: Students are encouraged to visit the faculty website: And most importantly the e-learning website: Nevertheless, feel free to contact me at:

3 3 Module Objectives: The course is devoted to: 1. The discovery and development of new agents for treating diseases. 2. Enable translating the drug structural formula into therapeutic effect. 3. Focus on the Structure-activity relationship (SAR) for some pharmaceutical agents. Why to study Organic Pharmaceutical Chemistry?

4 About This Module: Topics To Be Covered Cholinergic agents, cholinergic receptors and their subtypes. 2. Cholinergic agonists; stereochemistry and structure-activity relationships (SAR); products; cholinesterase inhibitors. 3. Cholinergic blocking agent; structure-activity relationships (SAR); Solanaceous alkaloid and analogues; synthetic cholinergic blocking agents and products; ganglionic blocking agents (neuromuscular blocking agents). 4. Analgesic agents (SAR of morphine, SAR of meperidine type molecules; SAR of methadone type compounds; N-methylbezomorphans, antagonist type analgesics in benzomorphans). 5. Analgesic receptors, endogenous opioids; Products; Antitusive agents; Antiinflammatory analgesics. 6. Adrenergic agents (Adrenergic neurotransmitters); Adrenergic receptors; Drugs affecting Adrenergic neurotransmission; Sympathomimetic agents; Adrenergic receptor antagonists. 7. CNS depressant; Benzodiazepines and related compounds; Barbiturates; CNS depressant with skeletal muscle relaxant properties; Antipsycotics; Anticonvulsants. 8. CNS Stimulants 9. Steroidal and nonsteroidal hormones

5 5 Why To Study Medicinal Chemistry? Medicinal chemistry and/or pharmaceutical chemistry is a discipline of chemistry where it is involved with design, chemical synthesis, and development of pharmaceutical agents. How to be a good pharmacist regarding medicinal chemistry?

6 6 CHOLINERGIC DRUGS AND RELATED AGENTS.

7 7 Overview: ACh was first studied in the frog heart in The regularity role of autonomic NS. How important is the ACh in the human physiology. Trials to create ACh agonists and antagonists. Treatment of certain diseases like Alzheimer, Parkinson, and novelty treatment of overactive bladder.

8 8 Drugs that mimic the action of ACh do so either by: 1. Acting directly on the cholinergic receptors in the tissue. 2. Inhibiting acetylcholine esterase. Chemicals that bind or compete with ACh for binding to the receptor MAY block cholinergic neurotransmission. What is the difference between the parasympathomimetic and parasympatholytic drugs?

9 9 Cholinergic Receptors There are two distinct receptor types for ACh those differ in: 1. Composition, 2. Location, 3. Pharmacological function, and 4. Have specific agonists and antagonists.

10 10 Cholinergic Receptors Nicotinic and muscarinic receptors. Why to use the above names? Nicotine. Muscarine. Nicotinic receptor: Is called ligand-gated ion channel. Why?

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13 13 Nicotinic Receptor Subtypes Nicotinic receptors located in the neuromuscular junction differ from those on neurons, such as those in the CNS and autonomic ganglia, in that they have different ligand criteria.

14 14 Nicotinic Receptors At The Neuromuscular Junction (N1 ) Are blocked by succinylcholine (Suxamethonium), d- tubocurarine, and decamethonium. Suxamethonium d- tubocurarine Decamethonium

15 15 Nicotinic Receptors At The Neuromuscular Junction (N1 ) Are stimulated by phenyltrimethylammonium.

16 16 Nicotinic Receptors At The Autonomic Ganglia (N2) blocked by hexamethonium and trimethaphan.

17 17 Nicotinic Receptors At The Autonomic Ganglia (N2) Stimulated by tetramethylammonium and dimethyl-4- phenylpiperazinium (DMPP).

18 18 Muscarinic Receptors Effects of ACh on the innervated organs? i.e. lungs, heart, smooth muscles, salivary glands. Etc. Muscarinic receptors may perform their effects via activating (GTP)-binding proteins (G proteins).

19 19 Muscarinic Receptor Subtypes According to pharmacology the muscarinic receptors are assigned M 1 to M 5. While according to the biochemical studies the muscarinic receptors are assigned m 1 to m 5.

20 20 M 1 Receptors E.g. M 1 receptors mediate gastric secretion. McN-A343 is a selective agonist (M 1 and M 4 ). Pirenzepine HCl (structure below) acts as an antagonist and has been used for the treatment of PU disease.

21 21 M 2 Receptors M 2 receptors mediate a decrease in the strength and rate of cardiac muscle contraction. M 2 receptors Act as autoreceptors on presynaptic terminals of postganglionic cholinergic nerves to inhibit ACh release... What about asthmatic patients? M 2 receptors are recognized by their high affinity for methoctramine.

22 22 M 3 Receptors M 3 receptors, defined as glandular muscarinic receptors, are located in exocrine glands and smooth muscle. M 3 effect is mostly stimulatory. Glandular secretions from lacrimal, salivary, bronchial, sweat, pancreatic, and mucosal cells in the GI tract are characteristic of M 3 receptor activation. Contraction of visceral smooth muscle is also a result of M 3 receptor stimulation.

23 23 M 4 Receptors M 4 receptors, like M 2 receptors, act through G protein to inhibit adenylate cyclase. They also function by a direct regulatory action on K + and Ca 2+ ion channels. M 4 receptors in tracheal smooth muscle, when stimulated, inhibit the release of ACh in the same manner that M 2 receptors do.

24 24 M 5 Receptors A great attention to study the M 5 receptor was performed because it has been thought that M 5 receptors may regulate dopamine release at terminals within the striatum. This was due to the presence of the (mrna) in the substantia nigra.

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26 26 Cholinergic Neurochemistry Cholinergic neurons synthesize, store, and release ACh. The neurons also form Choline-Acetyl Transferase (ChAT) and Acetyl Choline Esterase (AChE). What is the difference between the two enzymes?

27 27 ACh is prepared in the nerve ending by the transfer of an acetyl group from acetyl-coenzyme A (CoA) to choline. The reaction is catalyzed by ChAT. Choline is the limiting substrate for the synthesis of ACh. Most choline for ACh synthesis comes from the hydrolysis of ACh in the synapse. Choline is recaptured by the presynaptic terminal as part of a high-affinity uptake system under the influence of sodium ions to synthesize ACh.

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29 29 Several quaternary ammonium bases act as competitive inhibitors of choline uptake. Why?. Hemicholinium, and the triethyl analog of choline act at the presynaptic membrane to inhibit the high-affinity uptake of choline into the neuron. These compounds cause a delayed paralysis at repetitively activated cholinergic synapses and can produce respiratory paralysis in test animals. The delayed block is caused by the depletion of stored ACh, which may be reversed by choline.

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31 31 The synthesis of ACh from choline and acetyl-coa is catalyzed by ChAT. ChAT is inhibited in vitro by trans-n- methyl-4-(1- naphthylvinyl) pyridinium iodide.

32 32 Any Questions? References: Wilson and Gisvold s Textbook of Organic Medicinal And Pharmaceutical Chemistry, 12 th Edition. National Center for Biotechnology Information. PubChem Compound Database; CID=22475, (accessed Sept. 28, 2015). Walter Jahn, (2012). AP1: NEURON: LIGAND GATED CHANNELS, (accessed Oct. 24, 2015 at: