Taxol—a chiral auxiliary case study

Nature of science:

Advances in technology—many of these natural substances can now be produced in laboratories in high enough quantities to satisfy the demand. (3.7) Risks and problems—the demand for certain drugs has exceeded the supply of natural substances needed to synthesize these drugs. (4.8)

• Taxol is a drug that is commonly used to treat several different forms of cancer.
• Taxol naturally occurs in yew trees but is now commonly synthetically produced.
• A chiral auxiliary is an optically active substance that is temporarily incorporated into an organic synthesis so that it can be carried out asymmetrically with the selective formation of a single enantiomer.

Applications and skills:

• Explanation of how taxol (paclitaxel) is obtained and used as a chemotherapeutic agent.
• Description of the use of chiral auxiliaries to form the desired enantiomer.
• Explanation of the use of a polarimeter to identify enantiomers.

Guidance:

• The structure of taxol is provided in the data booklet in section 37.

• There is an unequal availability and distribution of certain drugs and medicines around the globe.

Utilization:

• Syllabus and cross-curricular links:
• Topic 20.2—synthetic routes
• Topic 20.3—stereoisomerism

Aims:

• Aim 8: Consider the ethical implications of using synthetic drugs instead of natural sources.