ELM7: Drug structures Flashcards
What are optical isomers?
Pairs of compounds where there’s a different configuration about one or more atoms
Non superimposable
Identical physical and chemical properties
Interact differently with biological systems
What is a chiral centre?
Carbon atom with four different things bound
What is constitutional isomerism?
Molecules have different forms due to rotation of bonds
What is geometric isomerism/cis-trans isomerism?
A double bond or ring structure prevents rotation of a bond
How can three point binding be used in pharmacology?
A drug with a chiral centre has higher affinity for a target matching three points rather than 2
What are the three systems of classifying enantiomeric pairs?
+ or -
D or L
R or S
What is the + or - classification of enantiomeric pairs?
Enantiomers are identical apart from the direction they rotate polarised light in
Clockwise is +
Anticlockwise is -
What is used to measure the rotation of polarised light?
A polarimeter
What is the D or L classification of enantiomeric pairs?
Based on how much a molecule relates structurally to glyceraldehyde
D is structurally related to + glyceraldehyde
L is structurally related to - glyceraldehyde
What is the R or S classification of enantiomeric pairs
Cahn Ingold Prelog system
R right or S left
What are the stages of working out the classification of an enantiomer using the Cahn Ingold Prelog system?
- Find chiral centre
- Prioritise substituents according to atomic number
- Rotate molecule so the lowest priority group faces backwards
- Highest to lowest is clockwise then R
What is an example of a stereoselective interaction?
Noradrenaline
The R enantiomer binds to B2 adrenoceptors 45x tighter than the S enantiomer