Furan linalool oxide

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

Cis- and trans 5-[2-hydroxyisopropyl]-2-methyl-2-vinyl-tetrahydrofuran (c/s/frans-furan-linalool oxides) 171/II and rosefuran 18 ... 

A)-Furan linalool oxide (monoterpene) Litchi chinensis (lychee truit) (Sapindaceae) OD-R... 

Damage to the flavor of "Asti Spumante" wines stored at 20 C when compared with samples held at 10 C was related to losses of linalool and glycosidic precursors of linalool, geraniol and nerol (87). Also the concentrations of a-terpineol, hotrienol, nerol oxide and the furan linalool oxides increased in wines held at ambient temperature. Di Stefano and Castino (87) concluded that low temperature storage retarded these reactions and wines so held retained the characteristic muscat flavor for years. 

Fig. 4.5 Extent of hydrolysis of glycoside of different volatile compounds during MLF with four strains of malolactic bacteria (MLB). Values are calculated as a percentage ratio between the concentration of glycosides in MLF samples and in a non-MLF control. Sum of 1-hexanol, trans- and CM-3-hexenol, trans- and c/i-2-hexenol sum of isoamyl alcohols, heptanol, and 4-hydroxy-4-methyl-2-pentanol sum of benzyl alcohol and 2-phenylethanol sum of vanillin and benzaldehyde sum of 4-vinylphenol and 4-vinylguaiacol sum of Unalool and a-terpineol sum of nerol and geraniol sum of cis- and rrani-linalool oxides (pyranic and furanic) sum of 3,7-dimethyl-l,5-octadien-3,7-diol and the two 2,7-dimethyl-2,7-octadien-l,6-diol isomers (from Ugliano and Moio 2006, reproduced with permission)...

Figure 5.1a (1) cis and trans linalool oxide (5-ethenyltetrahydro-a,a,5-trirnethyl-2-furanmethanol) (furanic form) (2) linalool (3,7-dimethyl-l,6-octadien-3-ol) (3) a-terpineol (a,a,4-trimethyl-3-cycloexene-l-methanol) (4) (Z,E) ocimenol (2,6-dimethyl-5,7-octen-2-ol) (5) cis and trans linalool oxide (pyranic form) (6) citronellol (3,7-dimethyl-6-octen-l-ol) (7) nerol (Z), geraniol (E) (3,7-di-methyl-2,6-octadien-l-ol) (8) Ho-diendiol I (3,7-dimethyl-l,5-octadiene-3,7-diol) (9) endiol (3,7-dimethyl-l-octene-3,7-diol) (10) Ho-diendiol II (3,7-dimethyl-l,7-... 

The free volatiles consist mainly of linalool, geraniol, nerol, furan and pyran forms of the linalool oxides (17, 18, 19a, 20a respectively), a-terpineol, hotrienol 3 and citronellol 4a, which are also the major terpene aroma compounds of the fruit. 

The linalool oxides (109) are probably the oldest known of this group (Vol. 2, p. 165). They have been isolated after the action of Streptomyces albus on linalool (28), the optical activity at C-2 of the furan is the same as that of the starting linalool. This work also points out that rotations of the linalool oxides are different when measured neat or in solution. The oxidized linalool oxide 889 has been found in grape juice. It was synthesized by the action of silver carbonate on the dihydroxylinalool 108 (also occurring in grape juice), and dehydrating the hemiacetals 890 thus formed. ... 

Numerous other ethers containing pyran or furan rings are formed by the dehydration of aliphatic diols (e.g. linalool oxides, rose oxide or nerol oxide) and are components of many essential oils. For example, the furanoid 2R,5R)- E)- and (2J ,5S)-... 

Linalool has been used to prepare a mixture of terpenes useful for enhancing the aroma or taste of foodstuffs, chewing gums, and perfume compositions. Aqueous citric acid reaction at 100°C converts the linalool to a complex mixture, as shown in Fig. 8.26. A few of the components include a-terpineol (34%) (26), Bois de Rose oxide (5.1%) (129), ocimene quintoxide (0.5%) (130), linalool oxide (furan form) (0.3%) (131), cw-ocimenol (3.28%) (132), and many other alcohols and hydrocarbons (157). 

Epoxidation of linalool occurs at the more substituted double bond. Ring closure of this epoxide gives a mixture of the cis [5989-33-3] and trans [34995-77-2] isomers of the furan (131), and also the cis and trans isomers of the pyran (133) [14049-11-7] as shown in Fig. 8.27. This mixture is known as linalool oxide, and sometimes erroneously as epox-ylinalool or epoxydihydrolinalool. Linalool oxide has a sweet woody, floral powerful, sweet, and penetrating odor with earthy undertones. It is used in perfumes and in essential oil reconstitutions in which it adds a natural note to linalool. 

The Ti,Al-Beta shows both acidic and oxidative properties which is reflected in unwanted side-reaction. The group of Corma used the bifunctionality in the epoxidation/rearrangement of cx-terpineol to cineol alcohol and in the formation of furans from linalool.81,82 Similarly van Klaveren et al. applied Ti,Al-Beta in the one-pot conversion of styrene to phenyl acetaldehyde.83 Sato et alM solved the unwanted acid-catalyzed side reaction by neutralizing the acid site by ion exchange with alkali metals. Nevertheless the bifunctionality restricts the use of this catalyst to a limited number of reactions. 

Corma et aL [239] took advantage of both redox and acidic properties of Ti/Al-MCM-41 (Si/Ti = 68 and Si/Al = 196) aluminosOicate to carry out the multistep oxidation of linalool to cyclic furan and pyran hydroxy ethers (Scheme 6). 

The reaction was carried out in acetonitrile at 353 K using TBHP as oxidant. Conversions as high as 80 % were obtained. As shown in Scheme 6, it was postulated that the reaction takes place via epoxidation over Ti sites foUowed by acid catalyzed intramolecular opening of the epoxide ring by the 3-hydroxy group. Ti-6 zeolite gave somewhat lower conversions in addition to the preferential formation of furans over pyrans (ratio of ca. 1.5) due to shape selectivity. Ti-MCM-41 and gave furan to pyran ratios of ca. 0.9, comparable to those obtained by the epoxidase conversion of linalool. 

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