Pharmaceutical Chemistry III (MedicinalI)

Course Overview

Pharmaceutical Chemistry III, also known as MedicinalI, is an advanced undergraduate module that bridges the gap between basic organic chemistry and the practical design of therapeutic agents. The course emphasizes the relationship between molecular structure and pharmacological activity, focusing on the rational design, synthesis, and evaluation of drug candidates.

Key learning outcomes include:

• Interpretation of structureactivity relationships (SAR) for diverse drug classes.
• Application of modern synthetic methods to construct pharmacologically relevant scaffolds.
• Critical assessment of physicochemical and ADME (Absorption, Distribution, Metabolism, Excretion) properties.
• Design of lead optimisation strategies that balance potency, selectivity, and safety.

Core Topics

1. Medicinal Chemistry of Heterocycles

Heterocyclic rings such as pyridines, imidazoles, thiazoles and quinolines dominate modern drug space. The module covers synthetic routes, electronic effects, and how heteroatoms influence hydrogenbonding, lipophilicity, and metabolic stability.

2. Bioisosterism

Concepts of classical and nonclassical bioisosteres are explored. Students learn to replace functional groups to improve potency, reduce toxicity, or modulate physicochemical parameters. Examples include the replacement of a carboxylic acid with a tetrazole (e.g., angiotensinconvertingenzyme inhibitors).

3. Prodrugs and Drug Delivery

Design principles for prodrugs that enhance solubility, permeability, or target selectivity are examined. The section also introduces lipophilic and hydrophilic carrier systems, nanoparticle formulations, and the role of enzymatic activation.

4. TargetBased Design

Key molecular targets (GPCRs, kinases, proteases, ion channels) are discussed with respect to binding site topology, ligandreceptor interaction models, and the use of crystallographic data in virtual screening.

5. Computational Tools

Students gain handson experience with molecular docking, pharmacophore modelling, quantitative SAR (QSAR), and predictive ADME software. Emphasis is placed on interpreting output and recognizing limitations.

Drug Design Strategies

MedicinalI teaches three complementary approaches to lead discovery:

FragmentBased Lead Generation

Small, lowmolecularweight fragments are screened against a target. Hits are optimised by growing or linking fragments, producing highaffinity leads with good ligand efficiency.

StructureGuided Design

Highresolution Xray or cryoEM structures enable precise placement of functional groups to enhance key interactions (hydrogen bonds, stacking, metal coordination).

Phenotypic Screening Followed by Target Deconvolution

Compounds identified in cellbased assays are later dissected to pinpoint molecular targets, allowing retroactive optimisation based on SAR derived from the phenotypic data.

Laboratory Techniques Emphasised

The practical component reinforces theoretical concepts with handson synthesis and analysis:

• Multicomponent Reactions (MCRs): Ugi and Passerini condensations for rapid scaffold assembly.
• CrossCoupling Reactions: Suzuki, BuchwaldHartwig, and Negishi protocols for CC and CN bond formation.
• MicrowaveAssisted Synthesis: Reduces reaction times and improves yields for heterocycle construction.
• Purification and Characterisation: Flash chromatography, HPLC, NMR, HRMS, and elemental analysis to verify product identity and purity.
• InVitro Activity Screening: Enzyme inhibition assays, cellbased reporter assays, and preliminary cytotoxicity testing.
• ADME Profiling: Solubility, logP/D, plasma protein binding, and microsomal stability assays.

Assessment & Resources

Evaluation combines written, practical, and projectbased components:

• Midterm Exam (30%): Shortanswer and problemsolving questions covering SAR, synthetic routes, and pharmacokinetic concepts.
• Laboratory Report (20%): Detailed writeup of a selected synthesis, including rationale, data interpretation, and critical discussion.
• Group Design Project (30%): Teams design a novel inhibitor for a chosen target, produce a synthetic scheme, and present SAR analysis.
• Final Oral Presentation (20%): Individual presentation on emerging trends (e.g., covalent inhibitors, PROTACs, AIdriven design).

Recommended textbooks and online resources:

• Patrick G. TiradoRives, Medicinal Chemistry: The Modern Drug Discovery Process.
• Graham L. Patrick, An Introduction to Medicinal Chemistry.
• Online: RCSB Protein Data Bank for structural data.
• Software: Maestro (Schrdinger), Glide, and the free OpenBabel toolkit.