Drug Structures Flashcards
Enantiomers (2 answers)
- pairs of compounds in which there is a different configuration of substituents abut one or more atoms (chiral centers)
- non-superimposable mirror images of each other
Diastereoisomers
- molecules are not mirror images but which differ in the configuration of one or more chiral centers
- chiral centers found as well
Enantiomers similar properties
chemical and physical
Enantiomers different properties
differ in rotation of polarized light and how they interact with bioilogical systems
Example of achiral molecule
glycine- only 3 different types of groups attached to its alpha carbon (2H, NH2, COOH)
Conformational isomerism
molecules exist in different froms due to rotation of bonds
3 different systems
+/- optical activity
D/L (relationship to glyceraldehyde: amino acids and sugars)
R/S Cahn-Ingold- Prelog (universal and logical)
+/- optical activity process
randomly oriented light —> passes through polarizing filter —> shine polarized light through chiral sample—> if + will rotate light in clockwise direction and if - anti clockwise
(direction of light orientation)
D/L system process
configuration of molecule to glyceraldehyde (chiral)
D= related to + glyceraldehyde
L= related to - glyceraldehyde
When is D/L system used?
when obvious structural relationship between glyceraldehyde and molecule in question so ONLY works for sugars and amino acids
Limitations for D/L system (2)
- compounds that do not fit the rules are sometimes designated to D or L and can happen when molecule has amino acid as precursor
- in history D/L used +/- in optical activity
Example of limitation 1
L- noradrenaline
Example of limitation 2
L- nicotine
L- hyoscamine
Cahn Ingold Prelog limitation example
same L amino acids have different R S designations:
L- serine= (S) serine
L- cysteine= (R) cysteine
Cahn Ingold Prelog (CIP) (2 answers)
- enantiomers are R (rectus=right) or S (sinister= left)
- preferred system because allows you to determine structure of molecule from its designation and can be applied to any molecule
3 stages of RS system
1) finding chiral center
2) prioritizing substituents
Chiral center
C with 4 different substituents bonded to it
N, S, P can act as chiral centers but rare
Prioritizing substituents
done according atomic number of atoms bonded to chiral center
highest atomic number= prioritized
double/ triple bonds= treated as 2 or 3 single bonds to the same type of atom
if there is 2 of the same group choose priority according to whats bonded to each one (rank according to atomic number= higher atomic number group gets priority)
if there is no difference keep going down along chain
What arrangement does chiral carbon make?
carbon makes 4 single bonds in tetrahedral arrangement
Examples of stereoselective drug-target interactions
R- noradrenaline binds to beta 2 adrenoceptors around 45x titer than S- noradrenaline
Geometric isomerism
cis/trans
Stereoisomers
2^n (chiral centers)
