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Date November 2019 Marks available 1 Reference code 19N.3.hl.TZ0.26
Level HL Paper 3 Time zone TZ0
Command term Apply and State Question number 26 Adapted from N/A

Question

Taxol is an anticancer drug.

State the feature of Taxol that is a major challenge in its synthesis. Use section 37 of the data booklet.

[1]
a.

Describe how the challenge in (a) was resolved by pharmaceutical companies.

[1]
b.

Markscheme

numerous stereoisomers/chiral carbons/chiral centres/stereocentres/optical isomers ✔

NOTE: Accept exact number of chiral carbons ie 11, but do not accept just “chiral”.

a.

chiral auxiliaries/molecule binds to reactant blocking one reaction site «by steric hindrance»
OR
asymmetric synthesis / enantioselective catalysis «producing a specific enantiomer»
OR
biosynthesis / genetically modified bacteria/microorganisms ✔

NOTE: Accept “use of a chiral auxiliary leading to «the synthesis of» the desired enantiomer”.

b.

Examiners report

[N/A]
a.
[N/A]
b.

Syllabus sections

Additional higher level (AHL) » Topic 20: Organic chemistry » 20.3 Stereoisomerism
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Options » D: Medicinal chemistry » D.7 Taxol—a chiral auxiliary case study (HL only)
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Additional higher level (AHL) » Topic 20: Organic chemistry
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