Chirality & Odour Perception

Ionones, Irones, Damascones & Structurally Related Odorants

by John C. Leffingwell, Ph.D.

Photo by permission of M. Roudintska - Art & Parfum

Cyclic Terpenoid Odorants

Bicyclic Terpenoid Odorants

Acyclic Terpenoid Odorants

Ionones, Irones, Damascones & Structurally Related Odorants

Acyclics (Alcohols, Esters, Acids, Aldehydes)

Lactones & Furanones

Sesquiterpenoid Related Odorants

Steroid Urine Type Odorants

Sandalwood Type Odorants

Musk Odorants

Miscellaneous

Enantiomer & Odor Description
Odour Threshold (PPB)

Ionones, Irones, Damascones & Structurally Related Odorants

.

(R)-(+)-(E)-alpha-ionone - violet-like, fruity, raspberry-like, flowery, strong impact

0.03-328

(S)-(-)-(E)-alpha-ionone - woody, cedar wood like, raspberry & beta-ionone like

0.1-656

(R)-(-)-gamma-Ionone - Weak green, fruity, pineapple-like odor with metallic aspects, quite different from the typical ionone odor; however, slightly woody, ionone-type nuances are also present.

11

(S)-(+)-gamma-Ionone - Linear, very pleasant, floral, green, woody odor with a very natural violet tonality; the most powerful and pleasant isomer.

0.07

(R)-(+)-(E)-alpha-damascone - odor character was reminiscent of rose petals, with apple & fruitier notes than (S)-(-)-(E)-alpha-damascone . When used as a flavoring ingredient, (R)-(+)-alpha-damascone possesses also a somehat woody, camphory, dirty and musty taste.

100

(S)-(-)-(E)-alpha-damascone - floral, reminiscent of rose petals and characterized by a more pronounced and fresher floral note possessing moreover a green and slightly winey notes without presenting the "cork" tone and the typical green apple note of the racemic mixture or of the (R)-(+)-enantiomer. When used as a flavoring ingredient, (S)-(-)-alpha-damascone develops a floral note. Moreover, it is reminiscent of tea, especially with regard to its herbal character.

1.5

(R)-gamma-damascone - Liquorice, damascone-like, camphoraceous, inferior to the (S)-enantiomer

NA

(S)-gamma-damascone - Nice damascone character, camphoraceous

NA

Methyl (R)-alpha-cyclogeranate - a precious flowery, fruity, damascone-like fragrance

NA

Methyl (S)-alpha-cyclogeranate - characterised by a green, metallic, minty, camphoraceous note

NA

Methyl (R)-gamma-cyclogeranate - more common than (S)-enantiomer, camphoraceous, corky, cellar

NA

Methyl (S)-gamma-cyclogeranate - aromatic, damascone-like, thujone, fruity

NA

(+)-Methyl (1R,2S)-delta-cyclogeranate - Perfumers have also noticed some differences between the two enantiomers - although the odor of both enantiomers is clearly damascone-like and in the same trend described, the fragrance of the (1R,2S)-(+)- enantiomer is stronger than the (1S,2R)-(-)- enantiomer which, in the other hand, is more aromatic.

NA

(-)-Methyl (1S,2R)-delta-cyclogeranate - less strong and more aromatic than the (1R,2S)-(+)- enantiomer.

NA

Ethyl (R)-gamma-cyclogeranate - less fruity, aromatic, rosemary, less powerful than the (S)-enantiomer

NA

Ethyl (S)-gamma-cyclogeranate - aromatic, fruity, damascone-like

NA

Allyl (R)-gamma-cyclogeranate - more green, less blackcurrant, less floral, weaker than (S)-enantiomer

NA

Allyl (S)-gamma-cyclogeranate - green, floral, blackcurrant, aromatic, fruity, pleasant

NA

(1R,6S)-(+)-ethyl tetrahydrosafranate - clean and sweet floral

20

(1S,6R)-(-)-ethyl tetrahydrosafranate - dirty and heavy fatty floral

100

(1R,6S)-(-)-1,6-dihydrodamascone - ripe fruity odor with fresh rosy note

5

(1S,6R)-(-)-1,6-dihydrodamascone - slightly camphoraceous fruity odor like beta-damascone

0.75

(1'R,6'S)-(+)-1',2,3,6'-tetrahydrodamascone - heavy fruity

10

(1'S,6'R)-(+)-1',2,3,6'-tetrahydrodamascone - fruity odor with slight peach note

25

(1S,6S)-(+)-1,6-dihydroionone - very strong violet leaf odor like alpha-ionone (Yamamoto, et. al.); aromatic, carvone, woody, humus, powdery, ionone, myrrh, violet, strong (Chapuis & Brauchli)

25

(1R,6R)-(-)-1,6-dihydroionone - weak woody odor with chemical note (Yamamoto, et. al.); woody, ionone, leather, camphor, weak (Chapuis & Brauchli)

10

(R)-(+)-Dihydro-alpha-ionone - Floral, violet-type odor with slightly fruity aspects. Also possesses a woody side, but less pronounced than in dihydro-beta-ionone

31

(S)-(-)-Dihydro-alpha-ionone - Exhibits a floral orris-type odor, with woody aspects and a distinct honey note.

100

(R)-(-)-Dihydro-gamma-ionone - Emanates a fatty, earthy odor with floral, orris-type nuances

6.2

(S)-(+)-Dihydro-gamma-ionone - Fatty-floral odor, less orris-type than the other compounds of the dihydro series. An animalic undertone is also present.

39

(1R,6S)-(+)-Tetrahydroionone - Woody, powdery, amber, ionone

NA

(1S,6R)-(-)-Tetrahydroionone - Woody, cedar, powdery

NA

(-)-dihydro-beta-ionol - excellent retaining properties and a fine floral-musky type fragrance accompanied with a high-class feeling.

NA

(+)-dihydro-beta-ionol - excellent retaining properties and a fine floral-amber fragrance accompanied witha high-class feeling.

NA

(1R,6S)-(+)-tetrahydroionol - diffusive amber odor with slightly floral, orrisy and earthy note (Yamamoto et al.); also described as slightly floral and orris-lke amber fragrance (Ohmoto et al. for an ~95: 5 % ratio of trans/cis isomers)

400

(1S,6R)-(-)-tetrahydroionol - faint vetiver-like woody odor (Yamamoto et al.); also described as a very faint woody odor (Ohmoto et al. for an ~95: 5 % ratio of trans/cis isomers)

1000

(1'R,6'S)-(+)-1-(2',2',6'-Trimethyl-cyclohexyl)-pentan-3-one - Woody, irone, weak

NA

(1'S,6'R)-(-)-1-(2',2',6'-Trimethyl-cyclohexyl)-pentan-3-one - Amber, woody, saffron

NA

(1'S,6'S)-(+)-1-(2',2',6'-Trimethylcyclohexyl)-pent-1-en-3-one - Oily

NA

(1'R,6'R)-(-)-1-(2',2',6'-Trimethylcyclohexyl)-pent-1-en-3-one - Saffron, woody, floral

NA

(1'S,6'S)-(+)-1-(2',2',6'-Trimethylcyclohexyl)-hex-1-en-3-one - Liquor, quince, violet, woody, powdery

NA

(1'R,6'R)-(-)-1-(2',2',6'-Trimethylcyclohexyl)-hex-1-en-3-one - Woody, dry

NA

(1'R,3'S,6'S)-(+)-1-(2',2',3',6'-Tetramethyl-cyclohexyl)-pentan-3-one - Woody, weak, irone

NA

(1'S,3'R,6'R)-(-)-1-(2',2',3',6'-Tetramethyl-cyclohexyl)-pentan-3-one - Woody

NA

(1'S,3'S.6'S)-(+)-1-(2',2',3',6'-Tetramethylcyclohexyl)-pent-1-en-3-one - Woody, Orris, powdery, myrrh, balsamic

NA

(1'R,3'R,6'R)-(-)-1-(2',2',3',6'-Tetramethylcyclohexyl)-pent-1-en-3-one - Woody

NA

(1'R,6'S)-(+)-1-(2',2',6'-Trimethyl-cyclohexyl)-pentan-3-ol - very diffusive sharp amber odor with slight orrisy camphoraceous side note

56

(1'S,6'R)-(-)-1-(2',2',6'-Trimethyl-cyclohexyl)-pentan-3-ol - faint vetiver-like woody odor with slight amber and moldy note

890

4-methyl-1-[(1'R,6'S)-2',2',6'-trimethylcyclohexyl]pentan-3-ol - relatively powerless and slightly soil-like amber-like woody fragrance

NA

4-methyl-1-[(1'S,6'R)-2',2',6'-trimethylcyclohexyl]pentan-3-ol - very faint woody odor with a little moldiness

NA

1-[(1'R,6'S)-2',2',6'-trimethylcyclohexyl]heptan-3-ol - highly diffusible amber fragrance with slight orris-like side note

NA

1-[(1'S,6'R)-2',2',6'-trimethylcyclohexyl]heptan-3-ol - faint woody odor with a little moldiness

NA

(+)-(1'R,3'S,6'S)- Limbanol® = (+)-(1'R,3'S,6'S)-3'-methyl-norlimbanol - woody-amber odor of extraordinary intensity, together with a slight transpiration side note

NA

(-)-(1'S,3'R,6'R)-Limbanol® = (-)-(1'S,3'R,6'R)-3'-methyl-norlimbanol - a much weaker odor, albeit of similar character to the (+)-(1'R,3'S,6'S)-isomer

NA

(1'R,6'S)- (+)-5-methyl-norlimbanol - woody notes

NA

(1'S,6'R)- (-)-5-methyl-norlimbanol - woody notes but much weaker than the (+)-(1'R,6'S)-isomer

NA

(1'R,3R,6'S)- (+)-norlimbanol - very weak and devoid of animal character

NA

(1'S,3S,6'R)- (-)-norlimbanol - elegant woody-amber note, similar to the (1'R,3S,6'S) -isomer but much weaker

NA

(1'R,3S,6'S) -(+)-norlimbanol - strong very elegant woody-amber note strongest of 4 trans isomers

NA

(1'S,3R,6'R)-(-)-norlimbanol - very weak and devoid of animal character

NA

(1'S,3'S,6'S)-(E)-(+)-dihydroirone - iris-irone note with a very warm balsamic-myrrh, woody character. The violet-iris character is more pronounced than in (1'R,3'R,6'R)-(E)-(-)-enantiomer or the racemate and the odor note is even stronger

NA

(1'R,3'R,6'R)-(E)-(-)-dihydroirone - Woody, powdery, incense.
The description given for racemate is: iris-violet note, powdery, balsamic, reminiscent of myrrh, woody, exceptional strength and tenacity odor

NA

(1R,3S, 6S)-(+)-Tetrahydroirone - Woody, powdery, ambergris

NA

(1S,3R,6R)-(-)-Tetrahydroirone - Unpleasant

NA

(1S,5R)-(+)-cis-alpha-irone - iris, sweet irone odour, woody ionone, floral, fruity (Galfry, et.al, by GC sniffing); Violet like, with woody, methylionone undertones (Brenna, et. al.)

100,000

(1R,5S)-(-)-cis-alpha-irone - odourless (Galfry, et.al, by GC sniffing); In contrast, Inoue, et. al., indicate the (-)-cis-alpha-irone fragrance is superior to its enantiomer; Brenna, et. al. describe it as slightly stronger with a distinct ‘orris-butter’ character

10,000

(1S,5S)-(+)-trans-alpha-irone - floral, fresh & fruity, irone and ionone type, honey, sweet chamomille effect, violet odour is weak (Galfry, et.al, by GC sniffing); Brenna, et. al. describe it as the weakest of the alpha-isomers

NA

(1R,5R)-(-)-trans-alpha-irone - iris, sweet irone charachter, dry odour (Galfry, et.al, by GC sniffing); Brenna, et. al. describe it as showing a "weak violet/wood/red berry character. Neither (+)- nor (-)-trans-alpha-irone possesses the characteristic ‘orris’ odour"

NA

(1S,5R)-(+)-cis-gamma-irone - iris, sweet, woody ionone, dry floral (Galfry, et.al, by GC sniffing); Inoue, et. al., indicate the (-)-cis-gamma-irone fragrance is Floral, green; weak; Brenna, et. al. describe it as showing a floral, fatty, sweet, and woody odour character, an ionone-type odour with slightly sweet aspects

0.1

(1R,5S)-(-)-cis-gamma-irone - odourless (Galfry, et. al.); In contrast, Inoue, et. al., indicate the (-)-cis-gamma-irone fragrance is superior to its enantiomer with Floral, sweet, ionone-like notes; Brenna, et. al. describe it as showing a "beta-ionone-type odour of warm floral-woody tonality. Green aspects are present, too. It shows some fruity nuances, reminiscent of pineapples. The odour is linear, and it can be considered a dry-down note"

0.00075

(1S,5S)-(-)-trans-gamma-irone - iris and floral note, ionone, like trans-alpha-irone (Galfry, et.al, by GC sniffing); Brenna, et. al. describe it as not very powerful, but it possesses a soft ‘orris-butter’-type of odour

0.02635

(1R,5R)-(+)-trans-gamma-irone - weak, burnt smell, metallic, chemical (Galfry, et.al, by GC sniffing); Brenna, et. al. describe it as very weak, of a woody odour tonality

0.1135

(5R)-(+)-beta-irone - iris family, anis, liquorice, green (Galfry, et.al, by GC sniffing); Brenna, et. al. describe it as possessing a beta-ionone-type odour of warm floral-woody tonality with green and anisic aspects. The odour is linear, and the tenacity of the note is good. It can be considered a dry-down note

NA

(5S)-(-)-beta-irone - poor, weakly iris (Galfry, et.al, by GC sniffing); Brenna, et. al. describe it as having a woody odour with a distinct honey note, that is quite sweet. Besides, it shows floral ionone-type facets, and a fruity tonality, but also an unpleasant smoky character. It belongs to the beta-ionone-type family, without being very close to beta-ionone

NA

(1S,6R)-(+)-trans-2,2,6-Trimethyl-cyclohexyl methyl ketone - Pleasant mint-like, camphor-like fragrance that is extremely sharp, strongly dispersing and characteristic

.NA

(1R,6S)-(-)-trans-2,2,6-Trimethyl-cyclohexyl methyl ketone - Characteristic marine, ozone and white floral fragrance in which the mint-like and camphor- like fragrance is weaker resulting in a softer aroma overall

NA

(1'R,2S,6'S)-(+)-1-(2',2',6'-trimethylcyclohexyloxy)-2-pentanol - amber, costus, Limbanol-type; dry, very powerful much more powerful than the three other possible optically active isomers. Its odour possesses a top note of the amber type which is particularly strong, accompanied by a woody note, less pronounced than in the other isomers. Its fragrance is also characterised by its dryness and an original costus note

NA

(1'S,2R,6'R)-(-)-1-(2',2',6'-trimethylcyclohexyloxy)-2-pentanol - woody, earthy, sesquiterpenes, lacks character; odoriferous notes of the woody type, but much less powerful than the (1'R,2S,6'S)-(+)-isomer

NA

(+)-(1'R,2R,6'S)-1-(2',2',6'-trimethyl-1'-cyclohexyloxy)-2-pentanol - woody, amber, lacks character

NA

(-)-(1'S,2S,6'R)-1-(2',2',6'-trimethyl-1'-cyclohexyloxy)-2-pentanol - woody, pencil, without character

NA

(+)- (1'R,2S,3'S,6'S)-1-(2',2',3',6'-tetramethylcyclohexyloxy)-2-pentanol - the best odorant ingredient of the series, amber, woody, dry, exceedingly powerful; possesses a fragrance which is much more intense and long-lasting than that of the other possible optically active isomers. Its extremely intense woody fragrance also has an amber-scented, dry, very natural character.

NA

(-)- (1'S,2R,3'R,6'S)-1-(2',2',3',6'-tetramethylcyclohexyloxy)-2-pentanol - woody, cedar, very weak to odorless; much weaker than the (+)-(1'R,2S,3'S,6'S)-isomer.

NA

(-)-(1'S,2S,3'R,6'R)-1-(2,2,3,6-Tetramethylcyclohexyloxy)-pentan-2-ol - woody, paper, slightly amber, weak;

NA

(+)-(1'R,2R,3'S,6'S)-1-(2,2,3,6-Tetramethylcyclohexyloxy)-pentan-2-ol - woody, amber, somewhat powerful

NA

(+)-(2S)-1-[(2,2,6,6-tetramethylcyclohexyl)oxy]butan-2-ol - amber, woody, cedar, strong

NA

(-)-(2R)-1-[(2,2,6,6-tetramethylcyclohexyl)oxy]butan-2-ol - celluloid, oil cloth

NA

(-)-(1'R,2S,2'S)-Ambercore® - amber, woody, dry, nice and strong

NA

(+)-(-)-(1'S,2R,2'R)-Ambercore® - woody, amber, very weak

NA

(+)-(1'S,2S,2'R)-Ambercore® - woody, amber, very weak

NA

(-)-(1'R,2R,2'S)-Ambercore® - without character

NA

(-)-(1'R,2S,2'S,5'R)-5-methyl-Ambercore® - amber, woody, not very powerful

NA

(+)-(1'S,2R,2'R,5'S)-5-methyl-Ambercore® - chalk, dusty, vaguely woody, weak

NA

(+)-(1'S,2S,2'R,5'S)-5-methyl-Ambercore® - floral, vague

NA

(-)-(1'R,2R,2'S,5'R)-5-methyl-Ambercore® - floral, vague

NA

(1'S,6'R)-(-)-1-(2',2',6'-Trimethyl-cyclohexyl)-hexan-3-one - Ionone, woody

NA

(1'R,6'S)-(+)-1-(2',2',6'-Trimethyl-cyclohexyl)hexan-3-one - Myroxyde, lavender, woody, ionone

NA

(2S,8aR)-3,4-Dihydro-3-oxoedulan - In the mixture of 2S,8aS (see below) and 2S,8aR isomers (2S,8aS : 2S,8aR ratio of 15:85), a camphoraceous note dominated

NA

(2R,8aS)-3,4-Dihydro-3-oxoedulan - In the mixture of of 2R,8aR (see below) and 2R,8aS isomers (2R,8aR : 2R,8aS ratio of 15:85), a weak tobacco note was detectable

NA

(2S,8aS)-3,4-Dihydro-3-oxoedulan - In the mixture of 2S,8aS and 2S,8aR isomers (2S,8aS : 2S,8aR ratio of 15:85), a camphoraceous note dominated

NA

(2R,8aR)-3,4-Dihydro-3-oxoedulan - In the mixture of of 2R,8aR and 2R,8aS isomers (2R,8aR : 2R,8aS ratio of 15:85), a weak tobacco note was detectable

NA

(2R,5RS)-Theaspirane - aroma of fruits, peach and honey, and sweet scent, clearly different from the racemate

NA

(2S,5RS)-Theaspirane - aroma of camphor, mint, wood, and eucalyptus, clearly different from the racemate

NA

(-)-(2R,5R)-Theaspirane - weak camphoraceous note

NA

(+)-(2S,5S)-Theaspirane - odor of isomer was dominated by a fresh camphoraceous note

NA

(+)-(2S,5R)-Theaspirane - a camphoraceous - almost naphthalene-like note

NA

(-)-(2R,5S)-Theaspirane - isomer exhibited a highly attractive, intense fresh-fruity (black currant or cassis) odor

NA

6S)-(+)-8,9-dehydrotheaspirone - Fruity-floral aroma (Kataoka, et. al.); floral, woody-ambery, powdery, reminiscent of Cetonal with natural fruity, orris-like facets (Serra, et. al.).

100

(6R)-(-)-8,9-dehydrotheaspirone - Woody aroma (Kataoka, et. al.); woody, dry, cedarwood odor with a green, earthy, tobacco and olibanum inflection and floral-fruity nuances (Serra, et. al.).

500

(+)-1-[(1R)-2,6,6-trimethylcyclohex-2-en-1-yl]acetone - a strongly diffusive floral-fruity odor with an iris-like note.

NA

(-)-1-[(1S)-2,6,6-trimethylcyclohex-2-en-1-yl]acetone - a weaker woody-animallic odor than that of the (S)-enantiomer.

NA

(+)-(1S,6R,8S)-Riesling acetal - woody, fruity, ionone, flowery note

NA

(-)-(1R,6S,8R)-Riesling acetal - slightly camphoraceous, flowery note

NA

(-)-(6R)-3,4-Didehydro-gamma-ionone - weaker than (+)-(S)-isomer, fruity-floral, slightly woody

0.25 ng/L in air

(+)-(6S)-3,4-Didehydro-gamma-ionone - stronger than (-)-(R)-isomer on blotter, floral-woody, cetonal-like, slightly fruity, damasconic, sweet

0.080 ng/L in air

(-)-(6R)-3,4-Didehydro-7,8-dihydro-gamma-ionone - weaker on blotter than (+)-(S)-isomer, fruity, agrestic, floral, ionone- and damascone-like, slightly woody, and saffron-like

99.4 ng/L in air

(+)-(6S)-3,4-Didehydro-7,8-dihydro-gamma-ionone - stronger on blotter than (-)-(R)-isomer, woody-powdery, ionone, slightly fruity-floral, more pronounced ionone character than (-)-(R)-isomer.

92 ng/L in air

(+)-(6R)-alpha-Iso-methylionone (ee = 94%) - typical dry warm ionone note, irisone, clean tea-like, also on blotter more intense and dryer than (-)-enantiomer.

0.079 ng/L in air

(-)-(6S)-alpha-Iso-methylionone (ee = 98%) - about ten times weaker floral note in the direction of iris and ionone, with hesperidic—citric elements and sweet fruity damascone-like aspects. More rich and complex in odour than (+)-enantiomer.

0.83 ng/L in air

(+)-(6R)-gamma-Iso-methylionone - Rich and interesting woody-ambery leather odour with fruity-floral facets in the direction of irone and methyl ionone and additional green accents.

NA

(-)-(6S)-gamma-Iso-methylionone - Woody-ambery mix odour between methyl ionone and Iso E Super of dry character.

NA

(+)-(6R)-alpha-n-Methylionone (ee = 93%) - woody, powdery, floral odour in the direction of the ionone family, but less powerful and less intense. Dry-down linear, after 4 h woody-ionone, somewhat orris-like, and after 24 h woody-ionone, fruity, raspberry-type.

0.53 ng/L in air

(-)-(6S)-alpha-n-Methylionone (ee = 98%) - woody, powdery, floral odour in the direction of the ionone family, but less powerful and less intense. Dry-down linear, after 4 h woody-ionone, somewhat orris-like, and after 24 h woody-ionone, only very slightly fruity.

0.24 ng/L in air

(-)-(6R)-gamma-n-methylionone - Woody odour in the direction of methyl ionone with additional dry, leathery aspects.

NA

(+)-(6S)-gamma-n-methylionone - Woody-floral odour in the direction of methyl ionone, with a fruity-floral violet inclination and facets of orris, but also an oily background.

NA

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