4. Biological synthesis reactions within cells ( in vivo) produce only one enantiomeric form. However, when drugs are produced by synthetic processes outside the body (in vitro), they yield a mixture of enantiomers known as a racemate.
Pharmaceutical companies face the challenge of finding out the physiological effects of each isomer, before determining whether the drug can be marketed as the racemic mixture or whether a single enantiomer must be produced.
The motivation for this research activity came from the thalidomide tragedy. Thalidomide was produced and sold as a racemic mixture. However, it was later discovered that only one of the isomers had a beneficial effect. The other isomer was teratogenic, meaning that it caused serious deformities in the fetus.

5. Many drugs are marketed as racemates, including fluoxetine (Prozac) and the anti-inflammatory drug Ibuprofen. However, it is becoming more common to develop drugs as single enantiomers.
It is estimated that of the chiral drugs on the market, approximately 50% are single enantiomers.

6. Taxol – a powerful anti-cancer drug
Taxol, also known as Paclitaxel, belongs to a group of compounds known as taxoids.
Taxol has potent effects against solid tumors and it is used primarily in the treatment of breast and ovarian cancers.
Taxol binds to a protein called tubulin in cells. Tubulin is the main component of microtubules, which form structures called spindles during cell division.
When the Taxol binds at the microtubules , it prevents the spindle fibers from breaking down, and this halts the cell division cycle. In this way taxol prevents the growth of a tumor.

10. Chiral auxiliary