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The Sequential Monte Carlo/Quantum Mechanics approach was used for investigate the solvent effect on the solute-solvent structure and spectroscopic properties of Damascone derivatives, Carvone, Perillaldehyde and Menthadiene in water solution. Our in-water results have shown that the dipole moment increase of the compounds are between 36% and 84% when compared with the gas phase values and a solvatochromic shift between −20 and 14 nm whereas the magnetic properties studied have indicated an NMR shift close to 10 ppm for some carbon atoms and greater than 140 ppm for oxygen atoms.

This review covers the synthesis of damascones and damascenones from their early discovery to nowadays starting from ionones, cyclic or linear starting materials. Gram-scale syntheses are highlighted.

Transfer of compounds across cellular barriers is a critical step of compound uptake into organisms. Using in vitro barrier systems to evaluate such transfer is attractive because of the higher throughput and reduced resource needs compared to animal studies. Thus far, however, studying the transfer of hydrophobic and volatile compounds was hampered by the unavailability of in vitro exposure systems that allow for stable and predictable chemical exposure concentrations. To overcome this limitation, we constructed a novel exposure chamber, TransFEr, and tested it with an in vitro epithelial barrier model using the rainbow trout (Oncorhynchus mykiss) intestinal cell line, RTgutGC. Key features of the chamber are its closed design and rotatable silicon segments, which can serve for chemical dosing and sampling. Using the fragrance damascone beta (log KOW: 3.7, log HLC: −3.9) as a pilot chemical, we were able to demonstrate that our exposure chamber provides for stable chemical exposure concentrations and full mass balance. The RTgutGC epithelium served as barrier for damascone beta transfer, which we attribute to chemical retention and biotransformation in the intestinal cells. Nevertheless, substantial transfer of the chemical across the epithelium occurred. When a chemical sink, i.e. a silicon segment, was included in the basolateral chamber to mimic blood constituents binding in vivo, transfer was about three-fold enhanced. We suggest that the presented methodology can help to obtain insights into chemical uptake mechanisms via the intestinal or other epithelia of fish and other animals for hydrophobic and volatile chemicals.

Following a request from the European Commission, the EFSA Panel on Additives and Products or Substances used in Animal Feed (FEEDAP) was asked to deliver a scientific opinion on the safety and efficacy of oct‐1‐en‐3‐ol [02.023], pent‐1‐en‐3‐ol [02.099], oct‐1‐en‐3‐one [07.081], oct‐1‐en‐3‐yl acetate [09.281], isopulegol [02.067] and 5‐methylhept‐2‐en‐4‐one [07.139], belonging to chemical group 5, and of isopulegone [07.067] and α‐damascone [07.134] belonging to chemical group 8, when used as feed flavourings for all animal species. They are currently authorised for use as flavours in food. The FEEDAP Panel was unable to assess the safety of isopulegone because the purity of the compound could not be established and the safety of α‐damascone [07.134] because of the inconclusive assessment of its genotoxicity. The FEEDAP Panel concluded that the use of isopulegol [02.067] is safe at the maximum proposed dose of 5 mg/kg complete feed for all animal species, except cats for which the use level of 1 mg/kg is considered safe. 5‐Methylhept‐2‐en‐4‐one [07.139] is safe at the proposed normal use levels of 1 mg/kg complete feed for all animal species. For oct‐1‐en‐3‐ol [02.023], pent‐1‐en‐3‐ol [02.099], oct‐1‐en‐3‐one [07.081] and oct‐1‐en‐3‐yl acetate [09.281], the calculated safe use level is 1 mg/kg complete feed for all animal species, except cats for which the calculated safe level is 0.6 mg/kg. No safety concern would arise for the consumer from the use of these compounds up to the highest safe levels in feed. In the absence of studies to assess the safety for the user, the FEEDAP Panel cannot conclude on the safety for the users when handling the additives. Use of the compounds in animal feed at the maximum safe level is considered safe for the environment. Since the compounds are used in food as flavourings and their function in feed is essentially the same, no demonstration of efficacy is necessary.

The silicon analogue of the potent spirocyclic δ-damascone odorant 6 was synthesized from allyltrichlorosilane (15) and but-2-en-1-ol (16). The latter was transformed to 3-methylpen-4-enenitrile (11) by Saucy-Marbet reaction with ethoxyethane and subsequent treatment with HONH2 ⋅HCl. The resulting γ,δ-unsaturated nitrile 11 was silylated with 1-allyl-1-chlorosilolane (14), which was prepared from allyltrichlorosilane (15) and the bis-Grignard reagent of 1,4-dichlorobutane. Metathetic ring closure employing the Grubbs I catalyst, followed by DIBAL reduction with non-aqueous work up, Grignard reaction with prop-1-en-1-ylmagnesium bromide, and Attenburrow MnO2 oxidation concluded the synthesis. The target compound was found to be olfactorily related to the spiro[4.5]-δ-damascone lead, but approximately 900 times weaker. In a type of enol Brook rearrangement, it thermally decomposes however to 3,6-dihydro-2H-1,2-oxasilocine (20), which surprisingly is a damascone odorant as well; although, 12 000 times weaker.

The dehydrogenative synthesis of β-damascenone from β-damascone via the related allyl bromide intermediate was studied in depth. The requisite dehydrobromination thereof was found strongly solvent system dependent. Under respective conditions, the product was identified as dehydrogenation-derived a, 4-alkoxy-derived b and 4-oxo-derived c, accordingly. In addition, the conversion from b to a was successfully accomplished, thereby offering an alternative access (with one step more) to reach β-damascenone. Copyright © 2016 John Wiley & Sons, Ltd.

The effects of dietary applied of β-damascone and its synthetic derivatives γ- and δ-halolactones, which show strong antifeedant activity, on the growth and development of larvae of the lesser mealworm, Alphitobius diaperinus Panzer (Coleoptera: Tenebrionidae), were studied. Bioassays were performed in a dose-dependent manner. In the bioassays, oat flakes treated with 1.0, 0.5, and 0.1 % (w/v) acetone solutions of the tested compound or acetone alone as control were served as food. The experiments were conducted using 2-week-old larvae with an average body weight of 4.35–4.88 mg. High correlations between antifeedant activity and larvicidal and growth-inhibitory effects were observed. Larvae reared on diets containing the compounds (at a concentration of 1 %) with high deterrent activity were characterized by a prolonged period of development, lower body weight gain, and strong tendency for cannibalism as a result of starvation. The control larvae ended their development after 24 days with a mean body weight of 22.9 mg. At the same developmental time, the mean body weights of larvae treated with the δ-halolactones γ-chloro- and γ-bromo-δ-lactone were only 60.3 % and 43.2 % of that of the control larvae. The larval periods for larvae on the diets containing γ-chloro- and γ-bromo-δ-lactone were 33 and 41 days, respectively. The larval developmental time and body weight gain were not significantly influenced by lower doses of the compounds, with the exception of γ-bromo-δ-lactone. This compound, when applied at a concentration of 0.5 %, significantly prolonged larval development as compared to the control larvae, and caused high mortality of larvae and pupae. The adult emergence percentage was 37.51 % when this treatment was applied, as compared to 90.0 % in the control. Thus, β-damascone derivatives with a lactone ring exhibit both dose-dependent behavioral effects and post-ingestion toxicity against A. diaperinus larvae, and may have the potential to control this pest.

Microbial conversion of β-damascone ( 1 ) into 4-hydroxy-β-damascone ( 2 ) was studied. The results showed the potential of the tested biocatalysts for the regio- and enantioselective hydroxylation of substrate 1 . The highest enantioselectivity was exhibited by strain Mortierella isabellina AM212. β-Damascone ( 1 ) was a relatively good deterrent towards Alphitobius diaperinus and it was behaviorally inactive to Myzus persicae . The racemic compound 2 and its (+)-( S )-enantiomer were stronger antifeedants against A. diaperinus than β-damascone ( 1 ), in the case of M. persicae only (+)-( S )-( 2 ) exhibited the deterrent properties.

α-Damascone is widely used in perfumes. However, the manufacture of α-damascone remains challenging owing to the limitations of current production processes. Herein, α-damascone was successfully synthesized from α-ionone using a new route involving only four steps, namely oximization, epoxidation, dehydration, and reduction. The total yield was 54.9% with a final chemical purity of 97% (by GC). Only water, cyclohexane, and ethanol were used in the reactions except in the purification step, and all solvents could be recycled. The structures of the intermediates and target compound were identified by 1H NMR and 13C NMR analyses and MS experiments. This route is a simple and successful method for the industrial preparation of α-damascone.

Starting from β-damascone, six new lactones were obtained. The Claisen–Johnson rearrangement of allylic alcohol and halolactonization of γ,δ-unsaturated acid were the key steps of the presented synthesis. The structures of the new derivatives were determined by spectroscopic data. The antifeedant activity of β-damascone towards two insect species with different feeding habits and food preferences, i.e., the peach-potato aphid Myzus persicae (Sulz.) and lesser mealworm, Alphitobius diaperinus Panzer, was studied, as well as the biological consequences of structural modification of the starting substrate. The successive structural modifications of β-damascone that resulted in the greatest antifeedant activity towards M. persicae were the incorporation of a lactone moiety and concomitant presence of bromine in the side chain. All β-damascone derivatives with a lactone moiety deterred the feeding of adults and larvae of A. diaperinus. Halo-δ-lactones were more active than halo-γ-lactones, and A. diaperinus adults were more sensitive to the compounds studied than larvae.

The oxidation of terpene olefins with hydrogen peroxide in the presence of the non-hemo catalyst 5a afforded mixtures of epoxides whose composition was dependent upon the oxidation protocol used in each case. With terpenoid enones, the mixtures obtained evolved from clean epoxidation of α-ionone 23 to the clean allylic oxidation of damascone 28 due to the progressive deactivation of the electron density on the double bonds present in this series. The oxidation of bicyclic and tricyclic terpenoids afforded oxidation products coming from epoxidation, to olefin degradation, methyne and methylene activation products. Probably, the most attractive result was the synthesis of the Magnus lactone 46 , from the tricyclic ether 45 , with 88% yield and 100% conversion.

The photochemistry of (E)-α- and (E)-β-damascone has been studied. Upon triplet-sensitized irradiation, both compounds exclusively undergo (E)-(Z) isomerization. (E)-β-damascone, upon direct irradiation with λ 254, 300 or 350 nm in non-alcoholic solvents, exhibits only (E)-(Z) isomerization. However, in an alcoholic solvent, direct irradiation induces cyclization and subsequent solvent incorporation, with formation of exo-8-alkoxy-1,5,5-endo-9-tetramethyl-cis-bicyclo[4.3.0]nonan-7-one (12). (E)-α-damascone, upon direct irradiation, exhibits α-cleavage with subsequent formation of the 1,3-acyl shift product, and equal amounts of the dimerization products of the allylic radical, viz.9 and 10. The 1,3-acyl shift product again undergoes photo-α-cleavage and the only products, upon prolonged irradiation, are the bicyclohexenyls 9 and 10.

1-(3,6,6-Trimethyl-1,3-cyclohexadien-1-yl)-2-buten-1-one (1), a β-damascenone isomer, was synthesized from 3,6,6-trimethyl-2-cyclohexenone (14). This starting ketone 14 was obtained in good yield from 3-methyl-2-butanone (11) and 3-buten-2-one (12). Ethynylation of 14 with 3-butyn-2-ol afforded acetylenic diol 20. Acid-catalyzed rearrangement of 20 yielded 1-(3,6,6-Trimethyl-1-cyclohexen-1-yl)-2-buten-1-one (2), a β-damascone isomer, was prepared from 1 by hydrogenation. Ketone 2 is shown to be identical to a naturally occurring compound found in fusel oil. 4-(3,6,6-Trimethyl-1-cyclohexen-1-yl)-3-buten-2-one (3), a β-ionone isomer, was obtained by condensation of 3,6,6-trimethyl-1-cyclohexenecarboxaldehyde (29) with acetone. Aldehyde (29) was synthesized from 2,2,5-trimethylcyclohexanone (16) by reaction of its tosylhydrazone 28 with n-butyllithium and DMF. The compounds 1–3, 17–21 and 25–29 are new. 1.

The effect of composition and origin of maltodextrins on the retention of 38 components in a mixture of volatile organic substances (odorants) during 6-month storage was studied by means of capillary gas-liquid chromatography. The retention of esters increased with an increase in their molecular weight. The retention of lactones, phenols, linalool, menthone, and damascone was 75–85%. Storage of aldehydes was accompanied by oxidation, and the retention of these substances did not exceed 55%. The retention of odorants increased with a decrease in the molecular weight of maltodextrins. The maximum retention was typical of maltodextrin from amylopectin starch not containing amylose.

γ‐ and δ‐Pyronenes are terpenic synthons easily available from myrcene. They are used as intermediates in the synthesis of α‐damascone, γ‐damascones, and β‐damascenone.

β‐Damascenone and β‐damascone derivatives, important fragrant compounds, were directly obtained from β‐ionone by a new way via retro‐α‐ionol.

A toxicologic and dermatologic review of trans-beta-damascone when used as a fragrance ingredient is presented.

A toxicologic and dermatologic review of gamma-damascone when used as a fragrance ingredient is presented.

A toxicologic and dermatologic review of trans,trans-delta-damascone when used as a fragrance ingredient is presented.

The aldehydes rac-1, rac-2, and 3 were conveniently prepared by starting from isophorone (4). Reaction of 1–3 with (E,Z)-1-bromo-1-propene (14) afforded the rac-allylic alcohols (E,Z)-15, -18, and -20. The alcohols were oxidized to the damascone/damascenone analogs 1-(3,5,5-trimethyl-2-cyclohexen-1-yl)- (rac-16), 1-(3,5,5-trimethyl-1-cyclohexen-1-yl)- (rac-19), and 1-(3,5,5-trimethyl-1,3-cyclohexadien-1-yl)-2-buten-1-one (21), and the (E/Z) isomers were separated by FC. Their olfactory evaluation shows that the highly estimated odor of damascone (A, B) and damascenone (C) is more or less lost. This result can be explained by force-field calculation of the lowest energy conformation of 16, 19, and 21 in comparison with those of A–C.

A straightforward enantioselective synthesis of both enantiomers of the title compounds is described starting from enantiopure methyl (2S,6R)- or (2R,6S)-cis-2-hydroxy-γ-cyclogeraniate. These versatile building blocks are obtained by biomimetic cyclization of methyl (6S)- or (6R)-(Z)-6,7-epoxy-7-methyl-3-(trimethylsilyl)methyl-2-octenoate, respectively. The chiral information was encoded by a highly regioselective Sharpless asymmetric dihydroxylation of the corresponding diene.

The scale-up of the HPLC separation of the enantiomers of the flavour norterpenoid ketones α-ionone and α-damascone from analytical to preparative scale was achieved using the chromatographic simulated moving bed (SMB) technique. Commercial HPLC columns, with heptakis-(2,3,6-per-O-methyl)-β-cyclodextrin bound to silica gel as chiral stationary phase, were employed for the separation. High-purity enantiomers of both chiral compounds have been obtained with a rather satisfactory productivity. Copyright © 2002 John Wiley & Sons, Ltd.

5,6,7-Trimethylocta-2,5-dien-4-one (3) was suspected of being a trace component smelling of damascone in a crude complex reaction product. Although this trace component eventually turned out to be the constitutional isomer 2-methyl-3-isopropylhepta-2,5-dien-4-one (4), the title compound 3 was found to possess even superior fruity, rosy odor characteristics, reminiscent of apples, plums, raisins and other dried fruits, and these odor characteristics are, surprisingly, due mainly to its (5Z)-isomer. The synthesis of 3 commenced with the preparation of 1-ethoxyprop-1-yne (11) from 2-chloro-1,1-diethoxyethane (9). Borontrifluoride-catalyzed addition of methyl isopropyl ketone (10) to 11 provided ethyl 2,3,4-trimethylpent-2-enoate (8), which was transformed into the target molecule 3 by Grignard reaction with propen-1-ylmagnesium bromide and in situ enolization. Further derivatives 13−16 provide more insight into the structure−odor correlation of damascone-type odorants, and the use of 3 in perfumery is illustrated by a composition formula of a demonstration perfume.

Poly(styrene-co-maleic anhydride)s were modified with poly(propylene oxide (PO)-co-ethylene oxide (EO)) side chains (Jeffamine®) with different EO/PO molar ratios, varying between 0.11 and 3.60. These copolymers were then further functionalized with a β-mercapto ketone of δ-damascone. The obtained poly(maleic acid monoamide)-based β-mercapto ketones were then studied as delivery systems for the controlled release of δ-damascone by retro 1,4-addition. The release of δ-damascone, a volatile, bioactive molecule of the family of rose ketones, was studied by dynamic headspace analysis above a cotton surface after deposition of a cationic surfactant containing fabric softening formulation, as a function of the ethylene oxide (EO)/propylene oxide (PO) molar ratio of the grafted copolymer side chains. The polarity of the EO/PO side chain influenced the release efficiency of the damascone in a typical fabric softening application. PO-rich copolymers and the corresponding poly(styrene-co-maleic anhydride) without Jeffamine® side chains were found to be less efficient for the desired fragrance release than the corresponding bioconjugate with a EO/PO ratio of 3.60 in the side chain. This copolymer conjugate seemed to represent a suitable balance between hydrophilicity and hydrophobicity to favor the release of the δ-damascone and to improve the deposition of the conjugate from an aqueous environment onto a cotton surface.

(R)-and (S)-γ-cyclogeranic acid ((R)-and (S)-9, resp.) were obtained by resolution of the racemate, and their absolute configurations determined by chemical correlation. The γ-acids (R)-and (S)-9 were converted into (R)-and (S)-methyl γ-cyclogeranate ((R)-and (S)-6, resp.), and (R)-and (S)-γ-damascone ((R)-and (S)-5, resp.). A more direct entry to (R)-and (S)-9 consisted in the enantioselective protonation of a thiol ester enolate with (−)- or (γ)-N-isopropylephedrine((−)- or (γ)-20) and subsequent hydrolysis of the (R)-and (S)-S-phenyl γ-thiocyclogeranate ((R)- and (S)-24, resp.; 97% ee). The esters (R)- and (S)-24 were also used as precursors of (R)- and (S)-γ-damascone ((R)- and (S)-5, resp.). Alternatively, (S)-5 (75% ee) was obtained by enantioselective protonation of ketone enolate 29 with (−)-N-isopropylephedrine ((−)-20). Organoleptic evaluation demonstrated that the (S)-enantiomers of methyl γ-cyclogeranate and γ-damascone are markedly superior to their (R)-enantiomers.

(R)- and (S)-α-ionone ((R)- and (S)-1, resp.) were prepared from (R)- and (S)-α-damascone ((R)- and (S)-3, resp.) without racemization in 48% yield employing a new enone transposition. The described transposition is complementary to existing methods whose application is often prohibited by the structural requirements of the substrate. The now easily accessible α-ionones of desired absolute configuration are useful as chiral building blocks for terpenoid synthesis.

(1993). A FACILE SYNTHESIS OF β-DAMASCONE. Organic Preparations and Procedures International: Vol. 25, No. 6, pp. 687-689.

(R)-and (S)-γ-cyclogeranic acid ((R)-and (S)-9, resp.) were obtained by resolution of the racemate, and their absolute configurations determined by chemical correlation. The γ-acids (R)-and (S)-9 were converted into (R)-and (S)-methyl γ-cyclogeranate ((R)-and (S)-6, resp.), and (R)-and (S)-γ-damascone ((R)-and (S)-5, resp.). A more direct entry to (R)-and (S)-9 consisted in the enantioselective protonation of a thiol ester enolate with (−)- or (γ)-N-isopropylephedrine((−)- or (γ)-20) and subsequent hydrolysis of the (R)-and (S)-S-phenyl γ-thiocyclogeranate ((R)- and (S)-24, resp.; 97% ee). The esters (R)- and (S)-24 were also used as precursors of (R)- and (S)-γ-damascone ((R)- and (S)-5, resp.). Alternatively, (S)-5 (75% ee) was obtained by enantioselective protonation of ketone enolate 29 with (−)-N-isopropylephedrine ((−)-20). Organoleptic evaluation demonstrated that the (S)-enantiomers of methyl γ-cyclogeranate and γ-damascone are markedly superior to their (R)-enantiomers.

Thujone, a waste by-product of the Canadian forest industry, has been utilized as a starting material to develop a versatile synthetic route to the damascones (rose oil ketones) and related analogues. The synthetic sequence provides a route to β-cyclocitral (45), the latter having been previously converted to β-damascone (2). In addition, thujone-derived intermediates are converted to β-damascenone (48) and to intermediates that can be utilized for the preparation of damascone analogues. In conjunction with the above, an efficient route to safronitrile (42), β-cyclogeranonitrile (43), and β-cyclocitral (45) from 2,6-dimethylcyclohexanone has been developed. In summary, these studies afford an attractive versatile route to these important perfumery materials.

(R)- and (S)-α-ionone ((R)- and (S)-1, resp.) were prepared from (R)- and (S)-α-damascone ((R)- and (S)-3, resp.) without racemization in 48% yield employing a new enone transposition. The described transposition is complementary to existing methods whose application is often prohibited by the structural requirements of the substrate. The now easily accessible α-ionones of desired absolute configuration are useful as chiral building blocks for terpenoid synthesis.

Structural comparison of apple constituents with known inducers of phase two cytoprotective enzymes led to the identification of 3-hydroxy-beta-damascone and related carotenoid derived aroma compounds as potent inducers of NAD(P)H:quinone reductase (QR) activity. Damascone-related compounds were found to be more potent inducers than ionone derivatives, with CD values (concentrations required to double the specific activity of QR in Hepa1c1c7 cell culture) in the range of 1.0-5.7 microM. QR induction by 3-hydroxy-beta-damascone was shown to be mediated via transcription factor Nrf2 signaling in transient transfection experiments. We further identified aroma compounds as potent inhibitors of LPS-induced inducible nitric oxide synthase activity in Raw 264.7 cell culture. Again, damascone derivatives were most potent with half-maximal inhibitory concentration values of 1.8-7.9 microM. These results reveal previously unrecognized cancer chemopreventive potential of aroma compounds such as beta-damascenone, 3-hydroxy-beta-damascone, and related substances, which may contribute to the cancer protective efficacy of apple products and other dietary sources in animal models.

The crystal structure of the zerovalent DIOP-platinum ethene complex has been determined. The complex has been used as a chiral derivatising agent for the analysis of the enantiomeric purity of cyclohexene derivatives, e.g. damascone, and certain chiral norbornenes.

The direct capillary gas Chromatographic separation oftrans-α-ionone andtrans-α-damascone enantiomers is reported using heptakis(2,3,6-tri-O-methyl)-β-cyclodextrin in polysiloxane as a suitable chiral stationary phase. The method described has been applied to determine the naturally occurring enantiomeric composition oftrans-α-ionone in the absolutes of the flowers ofBoronia megastigma Nees andOsmanthus fragrance Lour., Costus root oil (Saussurea lappa Clarke) as well as in odor concentrates of violet flowers (Viola odorata L.), fresh raspberries, carrots and vanilla pods. Furthermore, the optical purity oftrans-α-ionone in the solvent extracts of distilled alcoholic raspberry beverage, raspberry fruit juice concentrate and black tea was investigated.Trans-α-ionone was either isolated by headspace stripping in vacuo or by organic solvent extraction and subsequently enriched by multidimensional preparative Chromatographic techniques.Trans-α-damascone was isolated from Virginia tobacco extract and from black tea aroma and was enriched for direct chirospecific analysis by medium pressure liquid chromatography followed by multidimensional preparative capillary gas chromatography. The importance of chirality as an essential criterion for the discrimination of natural and nature-identical aromas is discussed briefly.

Bioconversion of α-damascone (compound 1) was studied with four strains of Botrytis cinerea in grape must (pH 3.2). As biotransformation products of compound 1, 3-oxo-α-damascone, cis - and trans -3-hydroxy-α-damascone, γ-damascenone, 3-oxo-8, 9-dihydro-α-damascone, and cis - and trans -3-hydroxy-8,9-dihydro-α-damascone were identified. In addition, acid-catalyzed chemical transformation of compound 1 to the diastereomers of 9-hydroxy-8,9-dihydro-α-damascone was observed. Identifications were performed by capillary gas chromatography (HRGC) and coupled HRGC techniques, i.e., on-line HRGC-mass spectrometry and HRGC-Fourier transform infrared spectroscopy, after extractive sample preparation.

Among the fragrance compounds synthesized by enantioselective protonation, (S)-alpha-damascone, (R)-muscone, and (S,S)-Vulcanolide are the most prominent ones. (S)-alpha-damascone has been prepared by four different procedures: from the magnesium enolate, from the lithium enolate, from the enol, and from the corresponding thiol ester. We now present a new, industrially viable protocol for the addition of allyl magnesium chloride to the 'cyclogeranoketene' by a Barbier reaction, followed by protonation of the ensuing magnesium enolate by an aggregate formed from (-)-N-isopropylephedrine, lithium isopropylate, and acetic acid, furnishing (S)-alpha-damascone in 91% yield and with 71% ee.

A toxicologic and dermatologic review of delta-damascone when used as a fragrance ingredient is presented.

β‐Damascenone and β‐damascone derivatives, important fragrant compounds, were directly obtained from β‐ionone by a new way via retro‐α‐ionol.

Enantioselective syntheses of ( S )-(+)-4-hydroxy-β-ionone and ( S )-(+)-4-hydroxy-β-damascone have been achieved through pig pancreatic lipase catalysed trans -esterification. These molecules find utility as constituent in fruit-type fragrance and flavor formulations and as chiral synthons in asymmetric synthesis of bioactive terpenoids.

An efficient highly enantioselective (eeor =99%) synthesis of alpha-ionone and alpha-damascone is described. Both enantiomers of title compounds were synthesized through two straightforward pathways diverging from enantiopure (R)- or (S)-alpha-cyclogeraniol. These versatile building blocks were obtained by regioselective ZrCl(4)-promoted biomimetic cyclization of (6S)- or (6R)-(Z)-6,7-epoxygeraniol, respectively, followed by deoxygenation of the so formed secondary alcohol. The chiral information was encoded by a highly regioselecive Sharpless asymmetric dihydroxylation of inexpensive geranyl acetate.