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Synthesis of natural fragrant molecules cis-3-methyl-4-decanolide and aerangis lactone. General enantioselective routes to beta,gamma-cis-disubstituted gamma-lactones and gamma,delta-cis-disubstituted delta-lactones.

General enantioselective routes to 3,4-cis-dialkyl substituted gamma-lactones and 4,5-cis-dialkyl substituted delta-lactones using TiCl(4)-mediated Evans asymmetric aldolization as the key step are reported. The syntheses are exemplified with two natural fragrant molecules, cis-3-methyl-4-decanolide (1) and aerangis lactone (2). The (R,R) steroegenic centers were established using (S)-phenylalanine-derived 2-oxazolidinone or thiazolidinethione as chiral auxiliary, whereas the (S,S) ones were constructed with auxiliary prepared from (R)-phenylglycine. NaBH(4)/CaCl(2)/THF in the presence of a small amount of EtOH was introduced as a new effective method for reductive cleavage of chiral oxazolidinone auxiliaries. Previously unknown, tricky concentration effects were observed during the monotosylation of diol 7 and BOM protection of Evans aldol 23.

Lactones↗

A general enantioselective approach to jasmonoid fragrances: synthesis of (+)-(1R,2S)-methyl dihydrojasmonate and (+)-(1R,2S)-magnolione.

Methyl dihydrojasmonate 1 and magnolione 3 are of both academic and industrial interest. In this paper, we describe a flexible, high-yielding route to diastereomerically pure (+)-cis-(1R,2S)-methyl dihydrojasmonate 1 and the first synthesis of (+)-cis-(1R,2S)-magnolione 3, both with enantiomeric excesses up to 93%. The two syntheses diverged from the same advanced intermediate 5, readily available from the enantioenriched hydroxymethyl delta-lactone (-)-(3aS,4S,6aR)-6. The olfactory properties of (1R,2S)-1 and (1R,2S)-3 are reported.

Catalysis↗

Enantioselective synthesis of both enantiomers of methyl dihydrojasmonate using solid-liquid asymmetric phase-transfer catalysis.

Both enantiomers of methyl dihydrojasmonate (-)-1 and (+)-1 were obtained by a short route using asymmetric Michael addition of dimethyl malonate onto pentyl enone 3, followed by nonracemizing demethoxycarbonylation. The key enantioselective step involves a new system of asymmetric solid-liquid phase-transfer catalysis using solvent-free conditions. Enantiomeric excess as high as 90% (91% yield) was achieved.

Catalysis↗

Contact allergens formed on air exposure of linalool. Identification and quantification of primary and secondary oxidation products and the effect on skin sensitization.

Linalool (3,7-dimethyl-1,6-octadien-3-ol) is an important fragrance chemical, frequently used in scented products because of its fresh, flowery odor. Linalool is an unsaturated hydrocarbon and is therefore susceptible to oxidation in the presence of air. The primary oxidation products, that is, hydroperoxides, formed in the autoxidation process, are reactive compounds that can be suspected to act as sensitizers. In the present investigation, we studied the autoxidation of linalool with emphasis on the formation of hydroperoxides. The oxidation products were isolated using flash chromatography and preparative HPLC and were identified with NMR and GC/MS, using synthesized reference compounds. Two hydroperoxides and several different secondary oxidation products were identified, among which some contain structural features that make them potential allergens. The amounts of linalool and the major oxidation products were quantified over time, using GC and an HPLC-method, suitable for the analysis of thermolabile primary oxidation products. The hydroperoxide 7-hydroperoxy-3,7-dimethylocta-1,5-diene-3-ol was found to be present in 15% in an oxidized sample. The local lymph node assay (LLNA) was used to investigate the sensitizing potential of pure linalool, two samples of air-exposed linalool, and oxidation products of linalool (an alpha,beta-unsaturated aldehyde, a mixture of two hydroperoxides, and an alcohol). Pure linalool showed no sensitizing potential. The air-exposed samples of linalool produced clearly positive responses, and the hydroperoxides were the strongest allergens of the tested oxidation products. The study demonstrates the importance of autoxidation on the sensitizing potential of linalool. We also conclude that the sensitizing potential differs with the composition of the oxidation mixture and thus with the air exposure time.

Acyclic Monoterpenes↗

Epidemiology of contact allergy in adults.

BACKGROUND: We aimed to determine the prevalence of contact sensitization in the general population and to investigate associations with important sociodemographic and medical characteristics. METHODS: Within a population-based nested, case-control study in Germany, we performed patch tests with 25 standard allergens in 1141 adults (50.4% female, age median 50 years). Additional information was obtained by a dermatologic examination, a standardized interview, and blood analysis. RESULTS: At least one positive reaction was exhibited by 40.0% of the subjects, with reactions most frequently observed to fragrance mix (15.9%), nickel (13.1%), thimerosal (4.7%), and balsam of Peru (3.8%). Women were sensitized more often than men (50.2% vs 29.9%, OR 2.36, CI 1.84-3.03), and this was also significant for fragrance mix, nickel, turpentine, cobalt chloride, and thimerosal. Contact sensitization was more frequent in subjects who reported adverse skin reactions (53.8% vs. 32.6%; OR 2.41, CI 1.85-3.14), and this was particularly true for sensitization to nickel (45.5% vs 8.8%, OR 8.64, CI 5.67-13.17) and fragrance mix (29.0% vs 14.0%, OR 2.51, CI 1.60-3.91) and the corresponding intolerance of fashion jewelry and fragrances. Contact sensitization decreased with increasing degree of occupational training (unskilled 45.9%, apprenticeship 40.1%, technical college 40.4%, and school of engineering 12.5%; P=0.023; trend test P=0.042). Significant associations of contact sensitization and presence of allergen-specific IgE antibodies, atopic eczema, or psoriasis were not observed. Frequency estimates for the general adult population based on these findings were 28.0% for overall contact sensitization and 11.4% for fragrance mix, 9.9% for nickel, and 3.2% for thimerosal. CONCLUSIONS: It is concluded that contact allergy is influenced by sociodemographic parameters and plays an important role in the general population.

Adult↗

Increase in contact allergy to fragrances: patch-test results 1989-1998.

We report the results of patch tests with fragrance-mix as a part of the standard series carried out over the last 10 years (1989-1998) during routine testing of 6129 patients in our department. 5.9% of the total number of patients who were patch tested were positive to fragrance mix. The sex ratio was 2.3:1 with a female predominance. In 1989-1993, the frequency of contact sensitivity to fragrance mix was 3.9% (4.9% for females and 2.1% for males). This rate rose both in female and male patients during the observed period of time and attained 8.9% (females) and 4.1% (males) in 1994-1998; the overall frequency in 1994-98 was 7.5%. This rising trend, which was statistically significant, might be the consequence of an increased use of cosmetics and toiletries containing fragrances in our population.

Allergens↗

Results of patch testing with lavender oil in Japan.

We report the annual results of patch testing with lavender oil for a 9-year period from 1990 to 1998 in Japan. Using Finn Chambers and Scanpor tape, we performed 2-day closed patch testing with lavender oil 20% pet. on the upper back of each patient suspected of having cosmetic contact dermatitis. We compared the frequency of positive patch tests to lavender oil each year with those to other fragrances. We diagnosed contact allergy when patch test reactions were + or <+ at 1 day after removal. The positivity rate of lavender oil was 3.7% (0-13.9%) during the 9-year period from 1990 to 1998. The positivity rate of lavender oil increased suddenly in 1997. Recently, in Japan, there has been a trend for aromatherapy using lavender oil. With this trend, placing dried lavender flowers in pillows, drawers, cabinets, or rooms has become a new fashion. We asked patients who showed a positive reaction to lavender oil about their use of dried lavender flowers. We confirmed the use of dried lavender flowers in 5 cases out of 11 positive cases in 1997 and 8 out of 15 positive cases in 1998. We concluded that the increase in patch test positivity rates to lavender oil in 1997 and 1998 was due to the above fashion, rather than due to fragrances in cosmetic products.

Adolescent↗

Contact allergy and hand eczema in Swedish dentists.

Hand eczema and contact allergy in Swedish dentists were studied in a multidisciplinary project. The aims of the study were to establish diagnoses, to investigate the occurrence of contact allergy, in particular to (meth)acrylates, and to evaluate certain consequences of hand eczema. A postal questionnaire on skin symptoms, atopy and occupational experience was mailed to 3,500 dentists aged <65 years, and licensed 1965-1995. The response rate was 88%. Among dentists living in 3 major cities, 14.9% (n= 191) reported hand eczema during the previous year. They were invited to a clinical examination, including patch testing with a standard and a dental series. 158/191 (83%) dentists attended, and hand eczema diagnosis was confirmed in 149/158 (94%). Irritant contact dermatitis was diagnosed in 67% and allergic contact dermatitis in 28%. On patch testing, 50% presented at least 1 positive reaction. The most frequent allergens were nickel sulfate, fragrance mix, gold sodium thiosulfate and thiuram mix. 7 (5%) had positive reactions to (meth)acrylates, all to 2-hydroxyethyl methacrylate and 6 also to ethyleneglycol dimethacrylate. 38% had consulted a physician, 4% had been on sick-leave and 1% had changed occupational tasks due to hand eczema. No dentist with allergy to acrylates had been on sick-leave or changed occupation. It is concluded that dentistry is a high-risk occupation for hand eczema, and that irritant contact dermatitis is most common. The prevalence of contact allergy to acrylates was below 1% in the population of responding dentists, and in most cases did not have serious medical, social or occupational consequences.

Adult↗

Multicentre study of allergic contact cheilitis from toothpastes.

The present work reports the results of a multicentre study of toothpaste allergic contact cheilitis (TACC) conducted by GIRDCA (Gruppo Italiano Ricerca Dermatiti da Contatto e Ambientali). The study examined 54 patients with eczematous lesions on the lips, the possible cause of which was suspected to be the use of toothpastes. Patch tests were conducted with a standard series, a specially-targeted series (toothpaste cheilitis series, TCS), and with suspected toothpaste(s). A stop-restart test (SRT) was carried out with these, together with a use test to identify possible alternative products. The TCS produced 17 positive reactions in 13 patients, the most frequent being to spearmint oil. Of the 54 patients, 5 displayed positive reactions only to the TCS. The patch tests with toothpaste produced positive reactions in 11/32 patients, the SRT a positive response in 10/12 cases. The diagnosis of TACC was confirmed in 15/54 patients. Alternative products were identified for 5 patients. In conclusion, the allergens most frequently responsible for TACC were the flavourings, and the additional series proved to be useful in many cases (together with patch tests with toothpastes and the SRT) for correct diagnosis and to initiate effective prevention.

Adolescent↗

Quenching: fact or fiction?

Fragrance chemicals are a frequently reported cause of allergic contact dermatitis (ACD), a matter which has recently come into considerable prominence, to the point that legislation in Europe is under serious consideration. Certain skin-sensitizing fragrance chemicals have been reported by the producing industry to be rendered safe (quenched), at least in terms of ACD, when they are used in the presence of a specific quenching agent. Accordingly, it seemed timely to review this apparent quenching phenomenon, considering the available data and potential mechanistic hypotheses that might be used to explain it. If it is correct, it should be a phenomenon of potentially enormous value in the elimination of the allergenic properties of at least a proportion of common skin sensitizers. Whilst there is some evidence in man for the occurrence of quenching during the induction of skin sensitization, a much more substantial body of work has failed to find supportive evidence in various animals models, at a chemical level or at elicitation in human subjects with existing allergy. On balance, it is concluded that quenching of fragrance allergens is a phenomenon still awaiting positive evidence of existence.

Chemical Industry↗

Fragrance contact dermatitis: a worldwide multicenter investigation (Part II).

The purpose of this study was to determine the frequency of responses to selected fragrance materials in patients who were fragrance sensitive. 178 patients were evaluated in 8 centers worldwide with a fragrance mix (FM) and 20 other fragrance materials. Reaction to the fragrance mixture (FM) occurred in 78.7% of the subjects. Substances reacting at a rate of 2% or higher included jasmine absolute, geranium oil bourbon, l-citronellol, spearmint oil, 1,3,4,6,7,8-hexahydro-4,6,6,7,8,8-hexamethylcyclopenta-gamma-2-benzopyran, omega-6-hexadecenlactone, dimethyltetrahydrobenzaldehyde (isomer mixture), and alpha-amylcinnamaldehyde. These chemicals should be furthur evaluated to corroborate their allergenicity. We are constantly looking for new fragrance allergens to extend the diagnostic capability of the fragrance mix (FM).

Allergens↗

Testing with fine fragrances in eczema patients: results and test methods.

The frequencies of contact allergic reactions to 2 fine fragrances were studied by patch testing. Further, a comparison was made of test results before and after evaporation of the solvent. A total of 480 consecutive eczema patients were included, 100 in the Dortmund clinic and 380 in the Gentofte clinic. Patch testing was done with 2 international brand prestige fragrances. Each fragrance was tested in duplicate. One was applied immediately and the other was allowed to dry for 5 min before application. Testing procedures and assessment of reactions followed the international recommendations. In Dortmund 11% (11/100) and in Gentofte 5.8% (22/380) gave a positive patch test reaction to one or both of the fine fragrances. Assessments done in Gentofte showed that in 73% of the cases the positive reaction indicated a clinically relevant fragrance allergy. More irritant reactions were found to the wet, non-evaporated form of the fragrances compared with the dried form, while the method of testing did not significantly influence the number of positive reactions. It is recommended that patch testing be performed with hydro-alcoholic fragrance products after evaporation of the solvent.

Adolescent↗

Fragrance chemicals in domestic and occupational products.

Epidemiological studies have described an increasing prevalence of fragrance allergy and indicated an association with hand eczema. 59 domestic and occupational products intended for hand exposure were subjected to gas chromatography-mass spectrometric (GC-MS) analyses to test the hypothesis that fragrance chemicals known to have the potential to cause contact allergy but not included in fragrance mix (FM) may be common ingredients in these products. A quantitative analysis of 19 selected fragrances was performed by GC-MS. Further analysis of GC-MS data revealed the presence of 43 other fragrance chemicals/groups of fragrance chemicals in the products investigated. Among the 19 target substances the most commonly detected were limonene in 78%, linalool in 61% and citronellol in 47% of the products investigated. The FM ingredients were present in these products with the following frequencies: oak moss (evernic acid methylester) 2%, cinnamic alcohol 2%, cinnamic aldehyde (cinnamal) 3%, isoeugenol 5%, alpha-amylcinnamic aldehyde (amyl cinnamal) 8%, hydroxycitronellal 12%, eugenol 27%, and geraniol 41%. Thus, the chemical analyses of domestic and occupational products indicates that investigation of potential contact allergy related to these products types should consider fragrance allergens additional to those in the FM, since these may occur with high frequency.

Dermatitis, Allergic Contact↗

Understanding fragrance allergy using an exposure-based risk assessment approach.

Conducting a sound skin sensitization risk assessment prior to the introduction of new ingredients and products into the market place is essential. The process by which low-molecular-weight chemicals induce and elicit skin sensitization is dependent on many factors, including the ability of the chemical to penetrate the skin, react with protein, and trigger a cell-mediated immune response. Based on our chemical, cellular and molecular understanding of allergic contact dermatitis, it is possible to carry out a quantitative risk assessment. Specifically, by estimating the exposure to the allergen and its allergenic potency, it is feasible to assess quantitatively the sensitization risk of an ingredient in a particular product type. This paper focuses on applying exposure-based risk assessment tools to understanding fragrance allergy for 2 hypothetical products containing the fragrance allergen cinnamic aldehyde. The risk assessment process predicts that an eau de toilette leave-on product containing 1000 ppm or more cinnamic aldehyde would pose an unacceptable risk of induction of skin sensitization, while a shampoo, containing the same level of cinnamic aldehyde, would pose an acceptable risk of induction of skin sensitization, based on limited exposure to the ingredient from a rinse-off product application.

Acrolein↗