Stereochemistry

Part 6: Resolution of Enantiomers

“Separating the inseparable: how chemists resolve mirror-image molecules.” Introduction Despite advances in asymmetric synthesis (Part 5), sometimes we still end up with a racemic mixture of enantiomers. When direct stereoselective routes are impractical, chemists must separate the enantiomers – a process known as resolution. This part examines classical and modern methods for resolving enantiomers, their pros and cons, and how they are applied in pharmaceutical contexts. We will cover: We’ll also discuss the racemic mixture …

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Part 5: Stereoselective and Stereospecific Synthesis

“Crafting molecules with precision – the art of stereochemical synthesis” Introduction Having seen why the correct stereochemistry is crucial for drug efficacy and safety, the next challenge is how to obtain the desired stereoisomer. This part covers strategies and methods in stereoselective and stereospecific synthesis. We clarify the terminology: a stereoselective reaction preferentially yields one stereoisomer over others (e.g., one enantiomer or one diastereomer is favored), whereas a stereospecific reaction produces different stereoisomeric products from …

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Part 4: Stereochemistry in Drug Action and Pharmacology

“Why one enantiomer heals while the other may harm – the pharmacology of chirality” Introduction Chirality doesn’t just influence drug properties in theory – it has very real consequences in pharmacology. In this section, we explore how stereochemistry affects drug action at multiple levels: pharmacodynamics (drug-receptor interactions) and pharmacokinetics (absorption, distribution, metabolism, excretion). We will define terms like eutomer (the more active enantiomer) and distomer (the less active one) and introduce the concept of the …

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Part 3: Nomenclature and Configuration

“Decoding the rules: how chemists name and navigate molecular twists.” Introduction Correctly describing the stereochemistry of a molecule is as important as understanding it. In this part, we focus on the Cahn–Ingold–Prelog (CIP) system, which provides the rules for unambiguous assignment of absolute configuration at stereocenters (R/S) and for double bond geometry (E/Z) system. We will outline the CIP priority rules step-by-step and demonstrate how to apply them to pharmaceutical molecules. Additionally, we will discuss …

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Part 2: Fundamental Concepts of Chirality

“From left- and right-handedness to life’s molecular signatures—chirality explained” Introduction Building on the overview of chirality, this section delves into core concepts: symmetry elements in molecules, the definitions of enantiomers and diastereomers, and the phenomenon of optical activity. Understanding these fundamentals is essential for grasping how stereochemistry manifests and is measured. We will also explore how chirality is quantified via optical rotation and how instruments like polarimeters help distinguish enantiomers. By the end of this …

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Part 1: Introduction to Stereochemistry

“The 3D language of molecules – why stereochemistry is the hidden key in drug science.” Introduction Stereochemistry is the branch of chemistry concerned with the three-dimensional arrangement of atoms in molecules and how this spatial arrangement influences chemical behavior. The term “chirality” (from the Greek cheir meaning hand) describes the property of an object or molecule that is non-superimposable on its mirror image – much like one’s left and right hands. A molecule that exhibits …

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