Perfumes hydroxycitronellal

Hydroxycitronellal is generally considered to have the odour closest in character to that of the natural product and has been used in such fragrances as Diorissimo which is a classic muguet type of perfume. Hydroxycitronellal is clearly terpenoid in origin, Lyral is prepared from a terpene, myrcene, and the structure of Lilial is very reminiscent of that of the p-menthane family of terpenoids. The syntheses of hydroxycitronellal and Lyral are both described in Chapter 3. All three of these materials contain aldehyde functions which limits their stability in oxidising media and in products where the pH is not neutral. There has therefore been a considerable amount of work on trying to find replacements for them and some examples are shown in Figure 10.11. 

Hydration of (R,E)-diethylenamine, followed by hydrolysis with sulfuric acid gives (+)-7-hydroxycitronellal, which is known as an artificial perfume with pleasant olfactory properties, with high optical purity (Scheme 5).9... 

Terpenoid alcohols appeared early in the history of synthetic perfumery because several were readily available from inexpensive essential oils. Alpha-terpineol, citronellol and linalool shown in Figure 7 are important constituents of pine stump oil, citro-nella oil and rosewood oil, respectively. The fourth material listed, hydroxycitronellal, is a hydroxy aldehyde which perhaps has a questionable place in this discussion. It is included because it is one of the most important fragrance chemicals used today. "Hydroxy" is almost a perfume unto itself. Its soft flowery, linden blossom odor blends very well in many floral perfumes. 

Initially, at the beginning of the present century, the traditional structure of the earlier perfumes was for the most part retained. "Fresh" natural materials such as bergamot and lemon, in combination with other essential oils, formed a large proportion of the composition, supported by animal and balsamic fixatives. To these were added the newly discovered synthetic and derived materials such as vanillin, coumarin, hydroxycitronellal, vetiveryl acetate, and methyl ionone, to-... 

Another technique much used in the past, though less popular today, was to take well-known products such as methyl ionone, vetiveryl acetate, or hydroxycitronellal—materials that themselves could often form 10-20% of a finished perfume—and decorate them with a number of other synthetic and natural materials to form a base with much of the complexity and "roundness of a finished perfume. Many such bases, for example, Althenol and Selvone (used in Ma Griffe), were created by Carles to be used not only by himself but also by client perfumers who lacked perhaps the same level of technical proficiency. 

The middle part of the perfume is a bouquet of floral notes reduced to their simplest components. Terpineol for lilac, styrallyl acetate for gardenia, phenylethyl alcohol for rose, hydroxycitronellal (10%) for muguet, and benzyl acetate and amyl cinnamic aldehyde for jasmin. 

Among the most important of these structural differences are the introduction of cis-3-hexenyl salicylate (6%) replacing part of the benzyl salicylate, and the replacement of hydroxycitronellal by Lyral (8%). Both changes are in keeping with the green, floral direction of the perfume. The woody and musk notes have also been modified and augmented by the introduction of newer materials such as Vertofix (3%) and ambrettolide. 

The green side of the perfume which is less pronounced than in Fidji, and more floral, is based on phenylacetaldehyde and cA-3-hexenyl acetate with perhaps a trace of galbanum. Narcisse absolute may also be used. Other materials that add to the building up of the white flower character are Lilial and cyclamen aldehyde in addition to the hydroxycitronellal and Lyral. The tuberose character can be given by the use of the Schiff base derived from methyl anthranilate and Helional, or by the direct addition of methyl anthranilate. The mossy side of the perfume is represented by Evemyl. 

As we would expect in a perfume as distantly related in time as Opium is to both Shalimar and Youth Dew, a number of more modem materials have been introduced. The cis-3-hexenyl salicylate backs up the benzyl salicylate, and Lyral, the hydroxycitronellal. A small amount of Hedione is also included. There have been important developments to the rose aspect of the perfume with the addition of phenylethyl dimethyl carbinol (3%) and Centifolyl. The fresh character of the rose derives from the use of geranyl acetate. Unlike the earlier oriental perfumes there is also an important aldehydic note. 

This combination of patchouli, hedione, rose, hydroxycitronellal, methyl ionone, and woody notes has been used in a number of subsequent perfumes including Coriandre, Aramis 900, Paloma Picasso, and Knowing, which can be thought of as forming a small but characteristic family. 

As we would expect the perfume is clearly composed around a classical structure of top, middle, and base notes. Apart from all the essential elements of a chypre there is the bold use of strong materials such as citronellal (1%), the aliphatic aldehydes (1%), styrallyl acetate (4%), and styrax in an accord that gives the perfume its enormous individuality. It was also part of Carles s technique to take structural materials such as vetiveryl acetate, methyl ionone, and hydroxycitronellal and dress them up with a number of natural and synthetic ma-... 

Apart from the materials already mentioned the top note contains a simple mixture of bergamot and orange. The middle note is dominated by a traditional jasmin base, with muguet (hydroxycitronellal 10%), and rose. At the heart of the perfume is the classical chypre accord between vetiveryl acetate (10%), methyl ionone, oakmoss, aldehyde C14, coumarin, sandalwood, patchouli, musk ketone, and amber. The amber note can be reproduced by the simple but effective combination of labdanum, olibanum, and vanilla. Small amounts of other animalic notes such as civet may also be used. 

A conventional jasmin base again provides the main floral aspect of the perfume. In more modem versions, for example, as in the Eau de Toilette, Lyral is used to replace part or all of the hydroxycitronellal. The styrax note may be reinforced by the use of phenylpropyl alcohol, one of its major constituents. The base note, in many ways similar to that of Ma Griffe, differs in the very much higher level of patchouli (10%). 

Not all new materials are entirely new. Many are, in their odor character, reminiscent of familiar ones the very first perfumer who smelled Lyral, for example, must have recognized its similarity to hydroxycitronellal. Others resemble familiar ones not only in their odor but also in the chemical structure c/.s-3-hexenyl salicylate was bound to find its place, if it had any at all, within the general area of the earlier known salicylates. 

The most classical artificial substances used in perfumery are as follows (Figure 5). Hydroxycitronellal (99) was found to exhibit the odor of lily of the valley, the essential oil of which is not possible to prepare in the first place. Other classics include ct-amylcinnamaldehyde (100) and musk ketone (101), which were discovered to be good substitutes for jasmine and musk, respectively. Furthermore, perfume No. 5 (Chanel, launched 1921) contained 2-methylundecanal, 1 with so unique an aroma character that it established No. 5 as the pioneer of a new fragrance class — floral aldehydic. 

Since the blossom oil of lily of the valley is not commercially available, the perfumers have to rely on synthetic substitutes, such as hydroxy-citronellal (1), Lilial (3) and Bourgeonal (6) to create their muguet fragrances. The oldest lily of the valley odorants, hydroxycitronellal and cyclamen aldehyde (2) (Winthrop Chem. Corp., 1929), were discovered by chance. Serendipity still continues to play an important role. Anselmi et al. (1992) synthesized and organoleptically screened a series of 38 tetrahydropyranyl ethers. This class of compounds was chosen because of their ease of synthesis and purification, and because of their stability in alkaline media, conditions under which aldehydes tend to undergo aldol condensations. Two compounds (24 and 25) were described as having a white, floral odour reminiscent of hydroxycitro-... 

Bourgeonal and hydroxycitronellal. Interestingly, a perfumer can often distinguish the typical odour of certain functional groups. Salicylates tend to have a woody character, which is modified by the length of the attached aliphatic chain or ring structure. Nitriles often smell somewhat metallic. Phenylacetates usually exhibit aspects of honey, etc. 

Perfume screening trays for patch testing has been developed to increase the sensitivity and specificity of perf ume allergy detection (Larsen 1977). In 20 perfume-sensitive patients examined with a screening tray of 15 fragrances, jasmin synthetic, cinnamic alcohol, and hydroxycitronellal were the three most common allergens. Rudzki and Grywa (1977 a) tested 35 essential oils and 4 balsams on... 

Uses Synthetic flavoring agent and fragrance in foods and pharmaceuticals fragrance in soap perfumes masking agent in cosmetics mfg. of hydroxycitronellal, insect repellent... 

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