Muscone

Muscone is an organic compound that is the primary contributor to the odor of musk.

Muscone
Names
IUPAC name
(R)-3-methylcyclopentadecanone
Identifiers
3D model (JSmol)
ChEMBL
ChemSpider
ECHA InfoCard 100.007.997
EC Number
  • 208-795-8
UNII
Properties
C16H30O
Molar mass 238.40 g/mol
Density 0.9221 g/cm3
Melting point −15 °C (5 °F; 258 K)
Boiling point 328 °C (622 °F; 601 K)
Hazards
NFPA 704 (fire diamond)
Flammability code 1: Must be pre-heated before ignition can occur. Flash point over 93 °C (200 °F). E.g. canola oilHealth code 1: Exposure would cause irritation but only minor residual injury. E.g. turpentineReactivity code 1: Normally stable, but can become unstable at elevated temperatures and pressures. E.g. calciumSpecial hazards (white): no code
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1
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Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Infobox references

The chemical structure of muscone was first elucidated by Leopold Ružička. It consists of a 15-membered ring ketone with one methyl substituent in the 3-position. It is an oily liquid that is found naturally as the (−)-enantiomer, (R)-3-methylcyclopentadecanone. Muscone has been synthesized as the pure (−)-enantiomer as well as the racemate. It is very slightly soluble in water and miscible with alcohol.

Natural muscone is obtained from musk, a glandular secretion of the musk deer, 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 "musky".

One asymmetric synthesis of (−)-muscone begins with commercially available (+)-citronellal, and forms the 15-membered ring via ring-closing metathesis:[1]

Synthesis of muscone via RCM

A more recent enantioselective synthesis involves an intramolecular aldol addition/dehydration reaction of a macrocyclic diketone.[2] Muscone is now produced synthetically for use in perfumes and for scenting consumer products.

Isotopologues 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.[3] It was found that the human musk-recognizing receptor, OR5AN1, identified using a heterologous olfactory receptor expression system and robustly responding to muscone, fails to distinguish between muscone and the so-prepared isotopologue in vitro.[3] OR5AN1 is reported to bind to muscone and related musks such as civetone through hydrogen-bond formation from tyrosine-258 along with hydrophobic interactions with surrounding aromatic residues in the receptor.[4]

See also

References
  1. Kamat, V. P.; Hagiwara, H.; Katsumi, T.; Hoshi, T.; Suzuki, T.; Ando, M. (2000). "Ring Closing Metathesis Directed Synthesis of (R)-(−)-Muscone from (+)-Citronellal". Tetrahedron. 56 (26): 4397–4403. doi:10.1016/S0040-4020(00)00333-1.
  2. Knopff, O.; Kuhne, J.; Fehr, S. (2007). "Enantioselective Intramolecular Aldol Addition/Dehydration Reaction of a Macrocyclic Diketone: Synthesis of the Musk Odorants (R)-Muscone and (R,Z)-5-Muscenone". Angew. Chem. Int. Ed. 46 (8): 1307–1310. doi:10.1002/anie.200604518.
  3. Block, E.; et al. (2015). "Implausibility of the Vibrational Theory of Olfaction". Proc. Natl. Acad. Sci. USA. 112 (21): E2766–E2774. Bibcode:2015PNAS..112E2766B. doi:10.1073/pnas.1503054112. PMC 4450420. PMID 25901328.
  4. Ahmed, L.; et al. (2018). "Molecular Mechanism of Activation of Human Musk Receptors OR5AN1 and OR1A1 by (R)-Muscone and Diverse Other Musk-smelling Compounds". Proc. Natl. Acad. Sci. USA. 115 (17): E3950–E3958. doi:10.1073/pnas.1713026115. PMC 5924878. PMID 29632183.
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