Damascones

2 Damascones. The damascones are isomers of the corresponding ionones in which the a,p-unsaturated function of the side chain has been transposed. They occur in rose oils and their name is derived from the Damask rose (Rosa damascena) in which they were first detected. They have powerful fruity odours with a hint of florality and rose character. 

The ready availability of ionones as potential starting materials, was exploited by Btichi in an elegant synthesis of p-damascone (8.69) and 

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Of all these, probably P-phenethyl alcohol (2) comes closest to the odor of fresh rose petals however, mixing all these components does not reproduce the total fine character of the natural oil. It has been determined that a number of trace constituents representing less than 1% of the volatiles are critical to the development of the complete rose fragrance (10). These include cis- and trans-i.ose oxide (1), nerol oxide (12), rose furan (13), /)i7n7-menth-l-en-9-al (14), P-ionone (15), P-damascone (16), and P-damascenone (3). 

KH/HMPT is also useful for selective 3-cleavage of tris(homoallylic) alcohols, as shown by a new synthesis of a-damascone (4). In general, l,l-dimethyl-2-pro-penyl and benzyl groups are cleaved more readily than a l-methyl-2-propenyl group,... 

Delivery receipt, 25 330 Delocalized cationic azo dyes, 9 423 Delta-3-carene (A-3-carene), 24 499 8-alumina, 2 404, 406t Delta coke, 22 704 8-damascone, 24 570... 

LInalool oxide-furan LInalool oxide-pyran 3-Hydroxy-p-damascone Fig. 18 Aromatic compounds occurring as glycosides... 

Examination of the flavour constituents of the passion fruit Passiflora edulis has yielded the novel ionone derivatives (47) and (48). Edulans 1 and II, (49) and (50), and dihydroedulans I and II, (51) and (52), from the same source have been characterized fully. Two bicyclodamascenones, (53) and (54), have been identified as components of the flavour of Virginia tobacco, and several ionone, damascone, and cyclocitral derivatives are present amongst the many volatile compounds produced during flue-curing of this tobacco. ... 

The acid-catalyzed cyclization of the chiral enamine (134) produces (R)-a-cyclocitral (135) and hence (R)-trans-a-damascone (136) in 33 % enantiomeric excess 152). 

Although a small amount of acyclic terpene acids such as geranic acid and citronel-lic acid occurs in many essential oils, often as esters, they are rarely used in perfume and flavor compositions. Methyl geranate is an intermediate in a-damascone synthesis and is sometimes needed in the reconstitution of essential oils. 

C13H20O, Mr 192.30, are ionone isomers. Depending on the position of the double bond in the ring, various isomers may exist. Commercially important are a-, (3-and -damascone. 

One synthetic route to the damascones starts with an appropriate cyclogeranic acid derivative (halide, ester, etc.). This is reacted with an allyl magnesium halide to give 2,6,6-trimethylcyclohexenyl diallyl carbinol, which on pyrolysis yields the desired l-(2,6,6-trimethylcyclohexenyl)-3-buten-l-one. Damascone is obtained by rearrangement of the double bond in the side-chain [98]. 

The a- and /3-damascones are used in perfume compositions, especially rose perfumes, and in flavor compositions, to which they impart naturalness and body. 

The material is prepared by Diels-Alder reaction of 1,3-pentadiene and mesityl oxide and subsequent aldol condensation of the resulting acetyl trimethyl cyclohexene with acetaldehyde [99]. 5-Damascone is used in perfumes to create masculine notes. 

Werkhoff P, Bretschneider W, Giintert M, Hopp R, Surburg H (1991) Chirospecific analysis in flavor and essential oil chemistry. Part B. Direct enantiomer resolution of trans-a-ionone and trans-a-damascone by inclusion gas chromatography. Z Lebensm Unters Forsch 192 111 Larsen M, Poll L (1990) Odour thresholds of some important aroma compounds in raspberries. Z Lebensm Unters Forsch 191 129... 

Zenoni G, Qrattrini F, Mazzotti M, Fuganti C, Morbidelli M (2002) Scale-up of analytical chromatography to the shmdated moving bed separation of the enantiomers of the flavor nor-terpenoids a-ionone and a-damascone. Flavour Fragr J 17 195... 

The thiolester was readily converted to target molecules, (S)-a-cyclocitral and (5)-a-damascone. 

Such routes have been used for the synthesis of natural products terpenes such as egomaketone (3-(4-methyl-3-pentenoyl)furan, perillene, ar-turmerone and iso-ar-turmerone [341], ar-curcumene [152], artemisia and isoartemisia ketones [342, 343], damascone [344], macrolides such as maysine [345], and pheromones with the sex attractant of the pine saw-fly [346],... 

Hydrogenation of 2,4,4-trimethyl-2-cyclohexenone with rrans-RuCl2(tolbinap)(dpen) and (CH3)3COK under 8 atm of hydrogen gives 2,4,4-trimethyl-2-cyclohexenol quantitatively with 96% ee (Scheme 1.70) [256,275,276]. In this case, unlike in the reaction of aromatic ketones, the combination of the R diphosphine and S,S diamine most effectively discriminates the enantiofaces. The chiral allylic alcohol is a versatile intermediate in the synthesis of carotenoid-derived odorants and other bioactive terpens such as a-damascone and dihydroactinidiolide [277]. 

Dihydroxylation of allylsilanes with OSO4 has been investigated extensively. The reaction has been used for the synthesis of /J-damascone 179 (equation 152)270. 

Amrollah-Madjdabadi and Stella used a similar approach for the rapid and concise synthesis of y-damascone (30) in three steps starting from allyl bromide (28) and dimethylaminoacetonitrile (29).21 These investi-... 

Today there are several thousand synthetically produced aroma chemicals potentially available to the perfumer. Many of these—for example, vanillin, the rose oxides, and the damascones—were first discovered in nature and subsequently synthesized. Others are the fruit of a chemist s imagination and have never been found in nature. Of course not all are of equal value to the perfumer, and the number that are widely used runs into the hundreds rather than into the thousands. 

Geraniol Citronellol beta Damascone Rose oxide Geranium Citronellyl acetate Phenyl ethyl alcohol Orthomethoxy benzyl ethyl ether... 

Paris also contains fruity notes, including alpha damascone and gamma-decalactone, which contrast with the green side of the violet accord. Violet and raspberry, both of which can contain ionones, form a natural association, and a trace of Frambinone can also work well in this context. 

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