MXPA97008523A - Optical isomers of derivatives of aldehido canfolen - Google Patents

Abstract

The present invention relates to a mixture of the 1'S, 2R, 3S; 1'S, 2S, 3R and 1'S, 2S, 3S; 1'S, 2R, 3R diastereoisomers of (E) -3-methyl-5- (2,2, 3-trimstylcyclopent-3-en-1-yl) pent-4-en-2-ol, a mixture of the diastereomers 1'R, 2S, 3R; 1'R, 2R, 3s and 1'R, 2R, 3R 1'R, 2S, 3s of (E) -3-methyl-5- (2,2,3-trimethylcycloopent-3-en-1-yl) pent-4-en-2-ol and for (1's, 2s , 3R) - (E) -3-methyl-5- (2,2,3-trimethylcyclopent -3-en-1-yl) pent-4-en-2-ol, (1'R, 2S, 3R) - (E) -3-methyl-5- (2,2,3-trimethylcyclopent -3-en-1-yl) pent-4-en2ol and for a process for the manufacture of these compounds or mixtures. In addition, the invention relates to any isomeric mixture of (E) -3-methyl-5- (2,2,3-trimethylcycloopent-3-en-1-yl) pent-4-en-2-ol enriched in a or both of the compounds or mixtures, especially to an odorant composition containing any isomeric mixture of (E) -3-methyl-5- (2,2,3-trimethylcyclopent-3-en-1-yl) p ent-4 -en-2-ol enriched in one of both of the above compounds or mixtures, and to the use of any of the compounds or mixtures as odorize

Description

OPTICAL ISOMERS OF CANFOLENIC ALDEHYDE DERIVATIVES DESCRIPTION OF THE INVENTION The present invention relates to the mixture of the diastereomers l'S, 2R, 3S; l'S, 2S, 3R and l'S, 2S, 3S; S, 2R, 3R of (E) -3-methyl-5- (2, 2, 3-trimethylcyclopent-3-en-1-yl) pent-4-en-2-ol, a mixture of the diastereomers l ' R, 2S, 3R; l'R, 2R, 3S; and l'R, 2R, 3R; R, 2S, 3S of (E) -3-methyl-5- (2,2,3-trimethylcyclopent-3-en-1-yl) pen-4-en-2-ol and al (1'S) , 2S, 3R) - (E) -3-methyl-5- (2,2,3-trimethylcyclopent-3-en-1-yl) pent-4-en-2-ol, (1 R, 2S, 3R) - (E) -3-methyl-5- (2,2,3-trimethylcyclopent-3-en-1-yl) pent-4-en-2-ol and to a process for the manufacture of these compounds or mixtures . In addition, the invention relates to any isomeric mixture of (E) -3-methyl-5- (2, 2, 3-trimethylcyclopent-3-en-1-yl) pent-4-en-2-ol enriched in one or in both of the compounds or mixtures, especially to an odorant composition containing any mixture of isomers of (E) -3-methyl-5- (2,2,3-trimethylcyclopent-3-en-1-yl) pent- 4-en-2-ol enriched in one or both of the above compounds or mixtures, and the use of any of the compounds or mixtures as odorants. Here and later in the present REF: 25801 by the term "enriched" is meant that one or both of the two compounds or mixtures mentioned at the beginning in an isomeric mixture of (E) -3-methyl-5- is present in excess. (2,2,3-trimethylcyclopent-3-en-1-yl) pent-4-en-2-ol, for example a particular isomer or mixture of isomers is present in an amount above the proportional amount. For example, a mixture of the 4 diastereoisomers of (1 'S) - (E) -3-methyl-5- (2, 2, 3-trimethylcyclopent-3-en-1-yl) pent-4-en-2 -ol is enriched in the l'S, 2S, 3R isomer if it contains more than 25% of the l'S, 2S, 3R isomer. In spite of the numerous studies in the domain of the derivatives of the canfolénico aldehyde, the prediction of the olfactory properties of different isomers and especially optical isomers, remains a difficult challenge. So far it is not possible to predict which absolute configuration of the five-ring ring carbon atoms and the side chain of such derivatives causes the strongest, most substantive and / or most natural sandalwood odor. Sandalwood oil from the East Indies has been described as "perhaps one of the most precious materials for perfumery from antiquity to modern times, and its popularity has shown no signs of language" (E. Guenther in "The Essential Oils" , Van Nostrand Company, Inc., New York, 1952, Vol.5, p.173). This oil is widely used in perfumery and could even be more widely used except for its limited supply and high cost. For many years there was a need for synthetic substitutes which could be used as sandal substitutes or as extenders. The activity in the analysis of sandalwood oil and the search for synthetic substitutes has been thoroughly revised (see E.-J. Brunke and E. Klein in "Fragance Chemistry- The Science of the Sense of Smell", ET Theimer, Ed., Academic Press, New York, NY 1982, p 397, KH Shankaranarayana and K. Parthasarathi, Perfu er and Flavorist, 9, 17, (1984), G. Ohloff, Ch. Fehr in "Perfumes - Art, Science and Technology" , PM Mueller, D. Lamparsky, Eds., Elsevier Science Publishers, London, New York 1991, pp. 298, G. Frater and D. Lamparsky, ibid, p 561). European Patent No. EP-A-203528 and the Patent No. 4,696,766 is related inter alia to the compound (E) -3-methyl-5- (2, 2, 3-trimethylcyclopent-3-en-1-yl) pent-4-en-2-ol which has the formula particularly with two pairs of enantiomers thereof. The compound has olfactory properties of sandalwood. It has been shown that the olfactory properties of (E) -3-methyl-5 ~ (2, 2, 3-trimethylcyclopent-3-en-1-yl) pent-4-en-2-ol depend on its configuration relative (see below). due to the three asymmetric centers (*) in the compound of formula I, eight optical isomers (four pairs of enantiomers) are expected. By gas-liquid chromatography on a Carbowax® 20M capillary column or by rotary band distillation, the compound was separated into a low boiling component into a higher boiling component. The upper gas-liquid chromatographic analysis on a capillary column of ethylene glycol succinate resolved each of these two components, confirming the presence of four diastereomer pairs of enantiomers. Thus the description refers to two pairs of low-boiling enantiomers, for example l'S *, 2R *, 3S * and l'S *, 2S *, 3R *, and two of higher boiling point, for example 1 , S * 2R *, 3S * and 1 'S *, 2S *, 3R *. It was reported that the two lower boiling pairs of the enantiomers are the organoleptically active compounds that possess a very intense creamy odor, wood, musk, sandalwood and are valuable ingredients for use in fragrance compositions with their qualities similar to musk and sandalwood. The mixture of these pairs of enantiomers is reported as more intense but any of the canhogenic aldehyde derivatives that have been previously reported. But nothing was decided on the odor of the simple enantiomers of the two most interesting pairs of the enantiomers, for example, l'S *, 2R *, 3S * and l'S *, 2S *, 3R *, or that of the other four stereoisomers which together constitute a successful raw material for perfumery, sold under the name of Ebanol. It should be noted that the above-mentioned low boiling enantiomer pairs are not commercially available. The four pairs of enantiomers are shown below: low boiling point low boiling point high boiling point lS (1'S, 2S, 3S) lfi (1'R, 2R, 3R) high boiling point As described in European Patent No. EP-A-203528 the mixture of diastereomers of compounds I are prepared in a sequence of steps as described below.

II III I Compound II is an α, β-unsaturated ketone which is converted to ketone III β, β-unsaturated, which is then converted to compound I by reduction of the ketonic carbonyl to the corresponding alcohol. Compound II is prepared from the campholenic aldehyde by an aldol condensation, whereby the camphoric aldehyde is prepared from α-pinene via the α-pinene epoxide. This is a process well known in the art, see for example U.S. Patent No. 4,052,341. It has now been found that knowledge of the olfactory properties of each of the simple optical isomers of this eight component mixture is crucial for the preparation of a better performance composition enriched in the most valuable isomer or isomer. This can significantly improve the quality of the commercialized raw material, offering more and better odor for the same weight, which is important not only for economic but also environmental reasons. In the synthesis of compound I according to the reaction described above, the configuration of the initial material of canophyenic aldehyde depends on that of a-pinene, which fixes the configuration of the Cl 'atom of the final product. The configuration of the other asymmetric carbons of the compound, located in the side chain, namely C2 and C3, is more difficult to influence, but can be discriminated either by the rapid development of asymmetric synthesis methods or by a relatively easy separation of the diastereoisomers. A systematic use of this recognition leads to the isolation of each simple stereoisomer of the eight constituents of compound I. Thus, the organoleptic properties of each stereoisomer could be determined. The above is shown schematically in Figures 1 and 2. If (IR) - (+) -a-pinene is used to produce the camphoric aldehyde via the pinene epoxide, the product is the aldehyde (S) - (-) - canpholic Using this campholenic aldehyde as starting material to produce a compound II and then carrying out a reaction according to the above description (as shown in figure 1 at the top), the four diastereomers la, Ib, le and Id of the compound are produced I. On the other hand, if (lS) - (-) - a-pinene is used to produce the camphoric aldehyde via pinene epoxide, the product is aldehyde (IR) - (+) - camphoric. Using this campholenic aldehyde as starting material for the production of compound II and then carrying out the reactions according to the above description (as also shown in figure 1), the other four stereoisomers are produced, namely 2a, 2b, 2c, 2d, of compound I. After the stereoisomers are separated by flash chromatography to produce two pairs of diastereoisomers, they are further separated by gas chromatography as shown in Figure 2. The final reduction of the ketone III can be brought to performed in an asymmetric manner (for example by the use of L-selectride) preferably producing the first two diastereomers eluted, or pairs of diastereomers of enantiomers: the + Ib or 2a + 2b. Consequently, if in the starting material the enantiomeric excess is different from 100%, two diastereomer pairs of the + Ib and 2a + 2b enantiomers are preferably obtained, as demonstrated in example 2 where the isomers (1 'S *, 2R *, 3S *) and (1 'S *, 2S *, 3R *) represent 79% of the product. In addition, Figure 2 shows the relevance of sandalwood odors as measured for each of the stereoisomers by determining their odor threshold. The threshold of odor or fragrance is a physical property of the composition, and defined as "its lowest concentration in the air, which can be consistently distinguished from pure air" (JE Moore in "Fragance Chemistry - The Science of the Sense of Smell", ET Theimer, Ed. Academic Press, New York, NY, 1982, p.34). The fragrance odor threshold value is expressed in terms of the odorant weight per volume unit of air as determined by olfactometry, a technique known to those skilled in the art and discussed by Amoore. In essence, the value of the odor threshold is the smallest amount of the odorant that must be present in a unit of volume of air to be detected, for example, distinguish it from the air itself. The details of the procedure and the results are described and simplified hereunder. Four pairs of diastereoisomers were synthesized and evaluated as such by the gas-sniffing chromatography technique, which allows to separately smell the two diastereomers of each part. In this way, the odor profiles and GC odor thresholds (gas chromatography) of the eight optical isomers of (E) -3-methyl-5- (2, 2, 3-trimethylcyclopent-3-en-) were obtained. l-il) pent-4-en-2-ol. The results are quantified in Figure 2. Unexpectedly, only one isomer of the two enantiomers of both enantiomeric pairs I S *, 2R *, 3S * and 1 'S *, 2S *, 3R *, proved to be the vector of the strong odor of natural sandalwood, namely l'S, 2S, 3R and l'R, 2S, 3R. These stereoisomers can each be obtained in pure form. The proportion of the odor intensity between these best stereoisomers (1 'S, 2S, 3R) / (1' R, 2S, 3R) is approximately ~ 3-5: 1. Its odors are much stronger and are apparently the only ones of the eight constituents of the mixture that impart to it the natural note of hot sandalwood and lactonic odor. This indicates that in this case the shape of the side chain as defined by the absolute configuration of the carbons C2 and C3, plays a key role in the perception of the essence of sandalwood and is more important than that of the asymmetric carbon of the carbocycle. The term "pure form" designates the present context a material that is substantially free of other stereoisomers, preferably having at least 90% optical purity, more preferably having at least 95% optical purity. The attribution to absolute configuration of all stereoisomers cited herein is based on the GC retention time of the diastereomer pairs of the enantiomers described in US Patent No. 4,696,766 and knowledge of the absolute configuration of the initial material. The (S) - (-) - camphoric aldehyde and its (R) + (+) - enantiomeric was synthesized according to the similar procedure starting from (lR) - (+) and (1S) - (-) -a -pinene respectively. Pinenos with enantiomeric excess (e.e.) >98% were provided by Aldrich. The campholenic aldehyde of Example 2 was obtained from an industrial quality of (IR) - (+) -a-pinene of e. and. = 43%. The optical purity of the enantiomers of the canpholénico aldehyde was measured with the aid of gas chromatography using a chiral stationary phase of OV-1701 / octakis (6-methyl-2,3-dipentyl) -? - cyclodextrin, and confirmed e. and. of the Pinenos. The gas chromatography analyzes of the reaction products and of the intermediates were carried out on a Megabore DB column of 5.30 m x 0.53 mm. Optical rotation measurements were performed on a Per-in-Elmer 241 polarimeter. The structure of the enantiomerically pure compounds and the mixtures of the diastereomers described in the examples, tested by their proton nuclear magnetic resonance (NMR) 1B spectra. and infrared 13C (IR) and mass spectrum, identical with those of the corresponding enantiomeric mixtures described in the aforementioned US Patent No. 4,696,766. All products synthesized are colorless oils.

Example 1 Preparation of (1 'S) - (E) -3-methyl-5- (2, 2, 3-trimethylcyclopent-3-en-1-yl) pent-4-en-2-ol and separation of its stereoisomers. a) Preparation of the (1 'S) - (E) -3-methyl-5- (2,2,3-trimethylcyclopent-3-en-l-yl) pent-3-en-2-one This compound was obtained as the corresponding enantiomeric mixture of Example II-1 of US Patent No. 4,052,341 starting from 18.0 g of (S) - (-) - camphoric aldehyde and 52.1 g of butan-2-one, and purified by distillation on a 5 cm Vigreux column. Yield: 15.1 g (62%). The product contained small amounts of other isomers, but was used without further purification in the next step. b) Preparation of the (1 'S) - (E) -3-methyl-5- (2,2,3-trimethylcyclopent-3-en-l-yl) pent-4-en-2-one 7. 0 g of the ketone from Example la) were added dropwise, during 30 min. to a stirred solution of 5.9 g of potassium tert-butoxide in 35 ml of dimethylformamide (DMF) at 10 ° C. The yellow reaction mixture was stirred for 5 h at room temperature, then cooled to 0 ° C, treated rapidly in 25 ml of 20% aqueous acetic acid and extracted with 200 ml of methyl tert-butyl ether. The extract was washed with 2 x 50 ml of water, dried (magnesium sulfate) and concentrated in vacuo to give 5.2 g of the crude product with a slightly yellow oil. Purification by flash chromatography on silica gel using a mixture of methyl tert-butyl ether / hexane 1:15 as eluent, gave 2.7 g (39% yield) of the (1 'S) - (E) -3- methyl-5- (2, 2, 3-trimethylcyclopent-3-en-l-yl) pent-4-en-2-one. GC purity: 96%; [a] D22 = + 51.5 ° (c 1.03, ethanol). c) Preparation of (1 'S) - (E) -3-methyl-5- (2, 2, 3-trimethylcyclopent-3-en-l-yl) pent-4-en-2-ol To a solution of 1.5 g of the ß, α-unsaturated ketone of Example Ib) in 10 ml of absolute ethanol was added dropwise at -5 ° C and under nitrogen atmosphere to 0.3 g of sodium borohydride suspended in 20 ml. of the same solvent. Stirring was continued for 20 h at room temperature and then the reaction mixture was poured into 150 ml of 0.1 N cooled with ice and extracted with 2 x 100 ml of MTBE. The extract was washed with 2 x 100 ml of brine, dried (magnesium sulfate) and concentrated in vacuo to give 1.5 g of pure product with GC with 93% (approximately quantitative yield) as a colorless oil. d) Separation of stereoisomers of (l'S) - (E) -3-methyl-5- (2,2,3-trimethylcyclopent-3-en-l-yl) pent-4-en-2-ol 1. 5 g of crude product from the previous step were separated by flash chromatography on silica gel using a mixture of methyl tert.-butyl ether / hexane 1: 5 as eluent. Two fractions were isolated only from the two constituents each: fraction 1 (0.5 g, GC purity:> 95%) contains a mixture -3: 2 of isomers (l'S, 2R, 3S) and (l'S, 2S, 3R); [a] D22 = + 24.5 ° (c 1.01, ethanol); Smell: sandalwood, dry, fresh, strong. fraction 2 (0.25 g, GC purity:> 95%) contains a mixture of isomers ~ 1: 1 (l'S, 2S, 3S) and (l'S, 2R, 3R); [a] D22 = + 27 ° (c 0.99, ethanol); Smell: celery, floral, fruity, fresh.

More than each isomer may have been isolated from less pure fractions. Both pure fractions were separated by gas chromatography on ethylene glycol succinate (LAC-4R-886) with a capillary glass column of 39 m × 0.3 mm. Its constituents are evaluated by the GC-sniff technique. The odor quality and the odor or fragrance thresholds of the simple molecules are described in Figure 2.

Example 2 Preparation of (E) -3-methyl-5- (2, 2, 3-trimethylcyclopent-3-en-1-yl) -pent-4-en-2-ol containing -28% of the isomer (1S, 2S , 3R) 22 ml of a 1M solution of L-Selectride in tetrahydrofuran (THF) was added dropwise, under nitrogen, at 0-5 ° C under stirring in 4.1 g of (E) -3-methyl-5- (2 , 2, 3-trimethylcyclopent-3-en-1-yl) pent-4-en-2-one prepared according to Example Ib from an industrial grade of (S) -campholenic aldehyde (ee 43%) and dissolved 40 ml of the same solvent. The reaction mixture was allowed to warm to room temperature and stirring was continued for 4 h. 20 ml of methanol and 200 ml of brine were added successively and the aqueous phase was extracted with 3 x 200 ml of methyl tert-butyl ether (MTBE). The combined organic phases were dried (magnesium sulfate), the solvent was evaporated in vacuo and the residue was purified by flash chromatography (MTBE / hexane = 1/4) followed by bulb to bulb distillation at 0.1 Torr. The product (2.8 g; 67% yield) contained 40, 39, 4.5 and 6.5% of diastereomeric pairs of the enantiomers (l'S *, 2R *, 3S *) f (l'S *, 2S *, 3R *), (1 'S *, 2S *, 3S *) and (1 'S *, 2R *, 3R *) respectively, the enantiomeric proportion of each pair is of l'S / l'R = 71.5: 28.5; [a] D22 = + 10. 5 ° (c 1. 00, ethanol),; smell: wood, sandalwood, amber with aspects of needles of cedar and pine, stronger and finer than Ebanol.

Example 3 Preparation of (1 'R) - (E) -3-methyl-5- (2, 2, 3-trimethylcyclopent-3-en-1-yl) pent-4-en-2-ol and separation of stereoisomers The following enantiomers (l'R) were prepared starting from the aldehyde (R) - (+) - camphorne in the same manner as their analogs (l'S) of example 1: a) (R) - (E) -3-methyl-5- (2,2,3-trimethylcyclopent-3-en-l-yl) pent-3-en-2-one b) (1 R) - (E) -3-methyl-5- (2,2,3-trimethylcyclopent-3-en-1-yl) pent-4-en-2-one purity GC: 98%; [a] D22 = 52. 5 ° (c 1, 06, ethanol). c) (R) - (E) -3-methyl-5- (2,2,3-trimethylcyclopent-3-en-l-yl) pent-4-en-2-ol d) Separation of stereoisomers of (l'R) - (E) -3-methyl-5- (2,2,3-trimethylcyclopent-3-en-l-yl) pent-4-en-2-ol 1. 5 g (almost quantitative yield) of the crude product from the previous step were separated by flash chromatography on silica gel using a mixture of methyl tert.-butyl ether / hexane 1: 5 as eluent. Two fractions were isolated only from two constituents each: fraction 1 (0.5 g, GC purity:> 91%) contains a mixture -3: 2 of isomers (l'R, 2S, 3R) and (l'R, 2R , 3S); [a] D22 = 25.5 ° (c 1.15, ethanol); odor: creamy, milky, sweet, sandalwood, weaker than that of the corresponding fraction 1 of the example Id. fraction 2 (0.32 g, GC purity:> 95%) contains a mixture of isomers -1: 1 (l'R, 2R, 3R) and (l'R, 2S, 3S); [a] D22 = 24.5 ° (c 1.01, ethanol); smell: celery, wood It could have been isolated more than each isomer from less pure fractions. Both pure fractions were separated and evaluated. The odor quality and odor thresholds were determined by the GC-sniffing technique as in the Id example and are presented in Figure 2.

Example 4 This example shows the advantage of the isomers according to the invention compared to the product Ebanol from the state of the art, which is a commercially available isomer mixture of (E) -3-methyl-5- (2, 2, 3-trimethylcyclopent-3-en-1-yl) pent-4-en-2 -ol. It produced a fine fragrance that contains the following ingredients. continuation [DPG = dipropylene glycol; DEP = diethyl dfatalate) When the amount of Ebanol used in this composition was replaced by twice less (by weight) of the 3: 2 mixture of (l'S, 2R, 3S) and (1 'S, 2S, 3R) - (E) - 3- methyl-5- (2,2,3-trimethylcyclopent-3-en-l-yl) pent-4-en-2-ol of Example Id, the sandalwood hue was retained from its odor and even strengthened. The sandalwood appearance was then accentuated by using less of the product.

Example 5 A fragrance was produced for a powder detergent or a softener with the following ingredients and compared with the same fragrance but containing the isomers of fraction 1 of Id example instead of Ebanol.

Continuation Comparing the two fragrances, the same effect was observed as in Example 4 on wet and dry linen after the washing or rinsing cycles. The systematic chemical names of the trivial names of the individual components mentioned above are listed in standard works, for example, Flavor and Fragrance Materials 1996, Allured Publishing Corporation, Carol Stream, Illinois, U.S.A. or Arctander, Perfume and Flavor Chemicals - 1969, published by the author, Montclair, New Jersey, E.U.A.

It is noted that in relation to this date, the best method known to the applicant to carry out the aforementioned invention, is that which is clear from the present description of the invention.

Having described the invention as above, property is claimed as contained in the following:

Claims (19)

1. A mixture of the diastereomers l'S, 2R, 3S; l'S, 2S, 3R and l'S, 2S, 3S; S, 2R, 3R of (E) -3-methyl-5- (2,2,3-trimethylcyclopent-3-en-1-yl) pent-4-en-2-ol.

2. A mixture of the diastereoisomers l'R, 2S, 3R; l'R, 2R, 3S and l'R, 2R, 3R; R, 2S, 3S of (E) -3-methyl-5- (2,2,3-trimethylcyclopent-3-en-1-yl) pent-4-en-2-ol.

3. The mixture according to claim 1 or 2 characterized in that it is in pure form.

4. (1S, 2S, 3R) - (E) -3-methyl-5- (2,2,3-trimethylcyclopent-3-en-1-yl) pent-4-en-2-ol.

5. (1R, 2S, 3R) - (E) -3-methyl-5- (2,2,3-trimethylcyclopent-3-en-1-yl) pent-4-en-2-ol.

6. The compound according to claim 4 or 5, characterized in that it is in pure form.

7. An isomeric mixture of (E) -3-methyl-5- (2,2,3-trimethylcyclopent-3-en-1-yl) pent-4-en-2-ol enriched in the mixture in accordance with any of the claims 1 to 3 and / or in at least one of the compounds according to claims 4 to 6.

8. A mixture of the compounds according to claims 4 to 6.

9. A process for the manufacture of the mixture according to any of claims 1 to 3, or of the compliant compound of any of claims 4 to 6, characterized the mixture or the compound is synthetically prepared.

10. A process for the manufacture of the mixture according to claim 1, or of this mixture in pure form characterized in that it comprises the use as initial material of (1 'S) - (E) -3-methyl-5- (2 , 2, 3-trimethylcyclopent-3-en-l-yl) pent-4-en-2-one (formula III ') and reducing this to (1' S) - (E) -3-methyl-5- ( 2,2,3-trimethylcyclopent-3-en-1-yl) pent-4-en-2-ol.

11. A process for the manufacture of the mixture according to claim 2, or of this mixture in pure form, characterized in that it comprises using as initial material the (1 'R) - (E) -3-methyl-5- (2 , 2, 3-trimethylcyclopent-3-en-l-yl) pent-4-en-2-one (formula III ') and reducing it to (1' R) - (E) -3-methyl-5- ( 2,2,3-trimethylcyclopent-3-en-1-yl) pent-4-en-2-ol.

12. A process for the manufacture of the compound according to claim 4, or of this compound in pure form, characterized in that it comprises the use as initial material of the (l'S) - (E) -3-meti1-5- (2,2 , 3-trimethylcyclopent-3-en-l-yl) pent-4-en-2-one and reducing it to (1 'S) - (E) -3-methyl-5- (2, 2, 3-trimethylcyclopent) -3-en-l-yl) pent-4-en-2-ol, whose intermediary product is a mixture of the diastereoisomers l'S, 2R, 3S; l'S, 2S, 3R and l'S, 2S, 3S; 1S, 2R, 3R, separating the mixture from the diastereoisomers and isolating the l'S, 2S, 3R isomer.

13. A process for the manufacture of the compound according to claim 5, or of this compound in pure form, characterized in that it comprises the use as initial material of the (l'R) - (E) -3-methyl-5- (2 , 2, 3-trimethylcyclopent-3-en-l-yl) pent-4-en-2-one and reducing it to (1 'R) - (E) -3-methyl-5- (2, 2, 3 -trimethylcyclopent-3-en-l-yl) pent-4-en-2-ol, whose intermediary product is a mixture of the diastereoisomers l'R, 2S, 3R; l'R, 2R, 3S and l'R, 2R, 3R; R, 2S, 3S, separating the mixture from the diastereoisomers and isolating the isomer lR, 2S, 3R.

14. The process according to claim 10 or 12, characterized in that the starting material (1 'S) - (E) -3-methyl-5- (2, 2, 3-trimethylcyclopent-3-en-1-yl) pent -4-en-2-one (formula III ') is synthesized from the aldehyde (S) - (-) - camphorne (formula IV) in a manner known per se.

15. The process according to claim 11 or 13, characterized in that the initial material (l'R) - (E) -3-methy1-5- (2,2,3-trimethylcyclopent-3-en-1-yl) pent -4-en-2-one (formula III ") is synthesized from the aldehyde (R) - (+) - camphorne (formula IV") in a manner known per se.

16. The use of the mixture according to any of claims 1-3, 7 or 8, or of the compounds according to any of claims 4 to 6 as an odorant.

17. An odorant composition, characterized in that it contains any isomeric mixture of (E) -3-methyl-5- (2,2,3-trimethylcpent-3-en-1-yl) pent-4-en-2-ol enriched in minus one of the mixtures according to claims 1-3, 7 or 8 and / or at least one of the compounds according to claims 4 to 6.

18. The process according to any of claims 10, 12 and 14 or 11, 13 and 15, characterized in that the initial material is present in an enantiomeric excess.

19. The process according to claim 18, characterized in that the reduction of the initial material is carried out in an asymmetric manner.