ELM7: Drug structures

Question 1

What are optical isomers?

Answer 1

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

Question 2

What is a chiral centre?

Answer 2

Carbon atom with four different things bound

Question 3

What is constitutional isomerism?

Answer 3

Molecules have different forms due to rotation of bonds

Question 4

What is geometric isomerism/cis-trans isomerism?

Answer 4

A double bond or ring structure prevents rotation of a bond

Question 5

How can three point binding be used in pharmacology?

Answer 5

A drug with a chiral centre has higher affinity for a target matching three points rather than 2

Question 6

What are the three systems of classifying enantiomeric pairs?

Answer 6

+ or -
D or L
R or S

Question 7

What is the + or - classification of enantiomeric pairs?

Answer 7

Enantiomers are identical apart from the direction they rotate polarised light in
Clockwise is +
Anticlockwise is -

Question 8

What is used to measure the rotation of polarised light?

Answer 8

A polarimeter

Question 9

What is the D or L classification of enantiomeric pairs?

Answer 9

Based on how much a molecule relates structurally to glyceraldehyde
D is structurally related to + glyceraldehyde
L is structurally related to - glyceraldehyde

Question 10

What is the R or S classification of enantiomeric pairs

Answer 10

Cahn Ingold Prelog system
R right or S left

Question 11

What are the stages of working out the classification of an enantiomer using the Cahn Ingold Prelog system?

Answer 11

1. Find chiral centre
2. Prioritise substituents according to atomic number
3. Rotate molecule so the lowest priority group faces backwards
4. Highest to lowest is clockwise then R

Question 12

What is an example of a stereoselective interaction?

Answer 12

Noradrenaline
The R enantiomer binds to B2 adrenoceptors 45x tighter than the S enantiomer