Chirality Flashcards
Define chirality.
An atom can be described as chiral if it is bound to four chemically different groups and can give a non-superimposable mirror image.
Define enantiomers.
Enantiomers are non-superimposable mirror images. They have the same physiochemical properties but differ in their interaction rotation of plane-polarized light.
Do enantiomers have the same affinities and actions at the active site/receptor?
They do not have the exact same affinities/actions but they can act in similar ways. Some enantiomers may be toxic so have to be removed from the mixture.
What is the name for a 50:50 mix of enantiomers?
A racemate.
What is a racemate?
A 50:50 mix of enantiomers.
Outline the Cahn-Ingold-Prelog rules.
- Prioritise each atom directly attached to the chiral centre from the highest atomic number to the lowest atomic number.
- LInk up the three highest priority atoms.
- Orientate the three atoms to look down the bond between the chiral centre and the lowest priority atom.
- Assign R if the priority goes clockwise, Assign S if the priority goes anti-clockwise.
If the chiral centre is assigned S conformation, which way does the priority go?
Anti-clockwise.
If the chiral centre is assigned R confirmation, which way does the priority go?
Clockwise.
Which conformation (R or S) of ibuprofen has analgesic properties?
S.
How is ibuprofen sold?
As a racemate.
The R enantiomer of ibuprofen has no analgesic properties, however, it has another property, what is this? How is this accounted for in dosing?
It is a teratogen. It shouldn’t be given during pregnancy, especially in the first trimester.
When the racemate is given, what enzymatic change occurs?
The R enantiomer is converted into the S enantiomer.
How much more active is the R enantiomer of salbutamol than the S enantiomer?
68x.
Is there any proven clinical benefit to giving just the R enantiomer over the racemate?
No.
Assign the properties of the R and S enantiomers of thalidomide.
R = anti-inflammatory. S = teratogenicity.
