May 20, 2024
Cats and berry bushes produce me.
What molecule am I?
Image of 4-Mercapto-4-methyl-2-pentanone 3D Image of 4-Mercapto-4-methyl-2-pentanone

4-Mercapto-4-methyl-2-pentanone (MMP) is an aliphatic ketone thiol that surprisingly shows up in  several natural settings. In 1948, MMP first appeared in the chemical literature in an article by Hungarian chemists Zoltán Földi and Jano Kollonitsch as an example of the addition of thiols across double bonds. The compound also appeared in articles by Russian and Turkish authors the same year.

MMP appears most often in the literature because of its characteristic olfactory property, that is, its foul smell. It is one of the three major odor components of cat urine, along with 3-mercapto-3-methylbutanol1 and 4-methoxy-2-methyl-2-butanethiol2. MMP is often called “cat ketone”.

But to some people, MMP resembles the aroma of blackcurrants, the fruit of the deciduous shrub Ribes nigrum. MMP’s low concentration in the currants gives them a somewhat pleasant smell that is still reminiscent of cat urine odor.

As our reader who suggested this molecule commented, “Cat ketone! Makes my blackcurrant tea and my cat boxes smell the same!” For more details on the currant–urine connection, see Andy Brunning’s excellent article “Blackcurrants & Cat Urine—The Chemistry of Blackcurrants”.

Finally, MMP shows up in other natural settings, such as Japanese green tea, Sauvignon grapes, and boxwood trees.

1. CAS Reg. No. 34300-94-2.
2. CAS Reg. No. 94087-83-9.

4-Mercapto-4-methyl-2-pentanone hazard information

Hazard class*GHS code and hazard statement
Flammable liquids, category 3H226—Flammable liquid and vaporChemical Safety Warning
Skin corrosion/irritation, category 2H315—Causes skin irritationChemical Safety Warning
Serious eye damage/eye irritation, category 2AH319—Causes serious eye irritationChemical Safety Warning
Specific target organ toxicity, single exposure, respiratory tract irritation, category 3H335—May cause respiratory irritationChemical Safety Warning

*Globally Harmonized System (GHS) of Classification and Labeling of Chemicals. Explanation of pictograms.

Molecule of the Future

Obeldesivir1 is a prodrug under development by Gilead Sciences (Foster City, CA) to combat two diseases. One of Gilead’s targets for obeldesivir is SARS-CoV-2, the virus responsible for COVID-19, in high-risk patients. The drug is given orally and converts enzymatically to the triphosphate form of Gilead’s remdesivir2, which must be administered intravenously. Obeldesivir is currently in Phase 3 trials for COVID-19.

Molecule of the Future

In the mid-2010s, Gilead developed remdesivir for treating Ebola viruses, among other targets, with modest success. This past April, Victor C. Chu at Gilead, Thomas W. Geisbert at the University of Texas Medical Branch (Galveston), and co-workers in both laboratories reported that oral administration of obeldesivir protects nonhuman primates against lethal infection by Sudan ebolavirus. The authors’ study showed that once-daily oral treatments of obeldesivir to cynomolgus monkeys (Macaca fascicularis) for 10 days beginning 24 h after exposure to S. ebolavirus provided 100% protection against lethal infection.

1. CAS Reg. No. 2647441-36-7.
2. CAS Reg. No. 1809249-37-3; Molecule of the Week for April 6, 2020.

Molecule of the Future

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4-Mercapto-4-methyl-2-pentanone fast facts

CAS Reg. No.19872-52-7
SciFindern name2-Pentanone, 4-mercapto-4-methyl-
Empirical formulaC6H12OS
Molar mass132.23 g/mol
AppearanceColorless to pale yellow liquid
Boiling point174 °C
Water solubility20 g/L (20 °C)
Chemical Abstract Service - a division of ACS

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