1) The (S) isomer is a highly potent therapeutic agent for primary chronic arthritis.
2) The (R) enantiomer has no therapeutic action, and it is highly toxic.
- Enantiomers may have distinctively different effects.
- The preparation of enantiomerically pure drugs is one factor that makes
enantioselective synthesis and the resolution of racemic drugs (separation into
pure enantiomers) active areas of research today.
5.13 STEREOISOMERISM OF CYCLIC COMPOUNDS
- 1,2-Dimethylcyclopentane has two stereocenters and exists in three stereomeric
forms 5 , 6 , and 7.
Me Me Me
Me
Me
Me
Me Me
H H
H
H
H
H
56 7
H H
Enantiomers Meso compound Plane of symmetry
1) The trans compound exists as a pair of enantiomers 5 and 6.
2) cis-1,2-Dimethylcyclopentane has a plane of symmetry that is perpendicular to
the plane of the ring and is a meso compound.
5.13A CYCLOHEXANE DERIVATIVES
- 1,4-Dimethylcyclohexanes: two isolable stereoisomers
- Both cis- and trans-1,4-dimethylcyclohexanes have a symmetry plane ⇒ have
no stereogenic centers ⇒ Neither cis nor trans form is chiral ⇒ neither is
optically active.
- The cis and trans forms are diastereomers.
