Table of Contents
What are the optical isomers of thalidomide?
Thalidomide exists in two mirror-image forms: it is a racemic mixture of (R)- and (S)-enantiomers. The (R)-enantiomer, shown in the figure, has sedative effects, whereas the (S)-isomer is teratogenic. Under biological conditions, the isomers interconvert, so separating the isomers before use is ineffective.
How many optical isomers does thalidomide have?
two
Thalidomide has just one chiral atom and so exists as two enantiomers.
Which isomer of thalidomide is bad?
Twenty years after the thalidomide disaster in the late 1950s, Blaschke et al. reported that only the (S)-enantiomer of thalidomide is teratogenic.
Did any thalidomide babies survive?
No-one knows how many miscarriages the drug caused, but it’s estimated that, in Germany alone, 10,000 babies were born affected by Thalidomide. Many were too damaged to survive for long. Today, fewer than 3,000 are still alive.
Did thalidomide affect all babies?
Some were still born or died very soon after birth. It is widely believed that as many as 100,000 babies were affected by the drug in total. It is generally estimated that over 10,000 babies were born worldwide and today fewer than 3,000 survive.
How do you identify R and S isomers?
If it is going clockwise, then it is an R-enantiomer; If it is going counterclockwise, it is an S-enantiomer.
How does optical isomerism occur in thalidomide molecule?
In order for optical isomerism to occur a chiral carbon has to be present. This is a carbon that is bonded to four different groups within the molecule. In the case of thalidomide there is only one chiral carbon in the molecule so only two possible isomers can occur.
What was the effect of thalidomide on animals?
L aboratory tests after the thalidomide disaster showed that in some animals the ‘S’ enantiomer was tetragenic but the ‘R’ isomer was an effective sedative. It is now known that even when a stereo selective sample of thalidomide (only one of the optical isomers) is created, if administered pH in the body, can cause racemizing.
How many chiral carbons are there in thalidomide?
This is a carbon that is bonded to four different groups within the molecule. In the case of thalidomide there is only one chiral carbon in the molecule so only two possible isomers can occur. However one of these isomers causes the birth defects that are unwanted and the other relieves morning sickness.
What’s the difference between thalidomide and S-enantiomer?
The ( R )-enantiomer, shown in the figure, has sedative effects, whereas the ( S )-isomer is teratogenic. Under biological conditions, the isomers interconvert, so separating the isomers before use is ineffective. More recently, thalidomide has proven useful for treating cancer and leprosy and is approved for these uses.