| Date | November 2016 | Marks available | 1 | Reference code | 16N.3.sl.TZ0.17 |
| Level | SL | Paper | 3 | Time zone | TZ0 |
| Command term | State | Question number | 17 | Adapted from | N/A |
Question
Oseltamivir (Tamiflu) and zanamivir (Relenza) are both used as antivirals to help prevent the spread of the flu virus, but are administered by different methods.
Zanamivir must be taken by inhalation, not orally. Deduce what this suggests about the bioavailability of zanamivir if taken orally.
Oseltamivir does not possess the carboxyl group needed for activity until it is chemically changed in the body. Deduce the name of the functional group in oseltamivir which changes into a carboxyl group in the body. Use section 37 of the data booklet.
The synthesis of oseltamivir is dependent on a supply of the precursor shikimic acid, which is available only in low yield from certain plants, notably Chinese star anise. State one alternative green chemistry source of shikimic acid.
Markscheme
«oral bioavailability is» low
OR
drug is broken down/pH too low/unable to be absorbed from gut
OR
only a small proportion of the drug «taken by mouth» reaches the target organ
ethoxycarbonyl/carbonyl attached to oxygen
Accept “ester”.
Any one of:
fermentation
OR
microbial production
genetically engineered bacteria/E.coli
sweetgum «seeds/leaves/bark»
OR
pine/fir/spruce tree «needles»
OR
Ginkgo biloba
Accept other specific examples of more plentiful plant sources.
