Muscone is an

organic compound In chemistry, organic compounds are generally any chemical compounds that contain carbon-hydrogen or carbon-carbon bonds. Due to carbon's ability to catenate (form chains with other carbon atoms), millions of organic compounds are known. The ...

that is the primary contributor to the odor of

musk Musk (Persian: مشک, ''Mushk'') is a class of aromatic substances commonly used as base notes in perfumery. They include glandular secretions from animals such as the musk deer, numerous plants emitting similar fragrances, and artificial sub ...

. The chemical structure of muscone was first elucidated by

Leopold Ružička Leopold Ružička (; born Lavoslav Stjepan Ružička; 13 September 1887 – 26 September 1976) was a Croatian-Swiss scientist and joint winner of the 1939 Nobel Prize in Chemistry "for his work on polymethylenes and higher terpenes" "including t ...

. It consists of a 15-membered ring ketone with one

methyl In organic chemistry, a methyl group is an alkyl derived from methane, containing one carbon atom bonded to three hydrogen atoms, having chemical formula . In formulas, the group is often abbreviated as Me. This hydrocarbon group occurs in many ...

substituent in the 3-position. It is an oily liquid that is found naturally as the (−)-

enantiomer In chemistry, an enantiomer ( /ɪˈnænti.əmər, ɛ-, -oʊ-/ ''ih-NAN-tee-ə-mər''; from Ancient Greek ἐνάντιος ''(enántios)'' 'opposite', and μέρος ''(méros)'' 'part') – also called optical isomer, antipode, or optical ant ...

, (''R'')-3-methylcyclopentadecanone. Muscone has been synthesized as the pure (−)-enantiomer as well as the

racemate In chemistry, a racemic mixture, or racemate (), is one that has equal amounts of left- and right-handed enantiomers of a chiral molecule or salt. Racemic mixtures are rare in nature, but many compounds are produced industrially as racemates. ...

. It is very slightly soluble in water and miscible with alcohol. Natural muscone is obtained from musk, a glandular secretion of the

musk deer Musk deer can refer to any one, or all seven, of the species that make up ''Moschus'', the only extant genus of the family Moschidae. Despite being commonly called deer, they are not true deer belonging to the family Cervidae, but rather their fa ...

, which has been used in perfumery and medicine for thousands of years. Since obtaining natural musk requires killing the endangered animal, nearly all muscone used in perfumery today is synthetic. It has the characteristic smell of being "

y". One asymmetric synthesis of (−)-muscone begins with commercially available (+)-

citronellal Citronellal or rhodinal ( C10 H18 O) is a monoterpenoid aldehyde, the main component in the mixture of terpenoid chemical compounds that give citronella oil its distinctive lemon scent. Citronellal is a main isolate in distilled oils from the p ...

, and forms the 15-membered ring via

ring-closing metathesis Ring-closing metathesis (RCM) is a widely used variation of olefin metathesis in organic chemistry for the synthesis of various unsaturated rings via the intramolecular metathesis of two terminal alkenes, which forms the cycloalkene as the ''E-' ...

A more recent enantioselective synthesis involves an intramolecular aldol addition/

dehydration reaction In chemistry, a dehydration reaction is a chemical reaction that involves the loss of water from the reacting molecule or ion. Dehydration reactions are common processes, the reverse of a hydration reaction. Dehydration reactions in organic ch ...

of a

macrocyclic Macrocycles are often described as molecules and ions containing a ring of twelve or more atoms. Classical examples include the crown ethers, calixarenes, porphyrins, and cyclodextrins. Macrocycles describe a large, mature area of chemistry. ...

diketone In organic chemistry, a dicarbonyl is a molecule containing two carbonyl () groups. Although this term could refer to any organic compound containing two carbonyl groups, it is used more specifically to describe molecules in which both carbonyls ...

. Muscone is now produced synthetically for use in

perfume Perfume (, ; french: parfum) is a mixture of fragrant essential oils or aroma compounds (fragrances), fixatives and solvents, usually in liquid form, used to give the human body, animals, food, objects, and living-spaces an agreeable scent. Th ...

s and for scenting consumer products.

Isotopologue In chemistry, isotopologues are molecules that differ only in their isotopic composition. They have the same chemical formula and bonding arrangement of atoms, but at least one atom has a different number of neutrons than the parent. An exampl ...

s of muscone have been used in a study of the mechanism of olfaction. Global replacement of all hydrogens in muscone was achieved by heating muscone with Rh/C in D₂O at 150 °C. It was found that the human

-recognizing receptor,

OR5AN1 Olfactory receptor 5AN1 is a protein that in humans is encoded by the ''OR5AN1'' gene. Olfactory receptors interact with odorant molecules in the nose, to initiate a neuronal response that triggers the perception of a smell. The olfactory receptor ...

, identified using a heterologous

olfactory receptor Olfactory receptors (ORs), also known as odorant receptors, are chemoreceptors expressed in the cell membranes of olfactory receptor neurons and are responsible for the detection of odorants (for example, compounds that have an odor) which give r ...

expression system and robustly responding to muscone, fails to distinguish between muscone and the so-prepared isotopologue ''in vitro''. OR5AN1 is reported to bind to muscone and related musks such as

civetone Civetone is a macrocyclic ketone and the main odorous constituent of civet oil. It is a pheromone sourced from the African civet. It has a strong musky odor that becomes pleasant at extreme dilutions. Civetone is closely related to muscone, the p ...

through hydrogen-bond formation from tyrosine-258 along with hydrophobic interactions with surrounding aromatic residues in the receptor.

References

{{reflist Flavors Perfume ingredients Macrocycles Ketones

See also

References