8-Hydroxy citronellol

Stereospecific syntheses of the eight stereoisomers [94] used a variation of the methodology developed in Mori s previous synthesis of the stereoisomers of 6,10,13-trimethyltetradecanol (see Scheme 5) [91], using chiral synthons derived from commercially available enantiomers of citronellol and methyl 3-hydroxy-2-methylpropanoate, and the iterative series of steps outlined in Scheme 13A for one of the stereoisomers [94]. A key step involved moving the... 

Therefore, (S)-3-hydroxy-2-methylpropanoic acid (1) is preferred over the structurally similar citronellol derivatives which have more, but often superfluous, carbon atoms and which are optically impure (ee values of 80%). Application of ent-2 in ex-chiral-pool synthesis is demonstrated in the preparation of ac-tocopherol (vitamin E)14. 

In the eighties, the bioconversion of monoterpene alcohols by fungi had not been studied intensively [32]. However, a strain of Aspergillus niger was isolated from garden soil, able to transform geraniol, citronellol and linalool to their respective 8-hydroxy derivatives. This reaction was called fu-hydroxylation [39,40]. 

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. 

Geraniol or nerol can be converted to citronellol in 96-99% ee in quantitative yield without saturation of the C(6)-C(7) double bond (eq 6). The S C ratio approaches 50000. The use of alcoholic solvents such as methanol or ethanol and initial H2 pressure greater than 30 atm is required to obtain high enantioselectivity. Diastereoselective hydrogenation of the enantiomerically pure al-lylic alcohol with an azetidinone skeleton proceeds at atmospheric pressure in the presence of an (i )-BINAP-Ru complex to afford the (3-methyl product, a precursor of ip-methylcarbapenem antibiotics (eq 7). Racemic allylic alcohols such as 3-methyl-2-cyclohexenol and 4-hydroxy-2-cyclopentenone can be effectively resolved by the BINAP-Ru-catalyzed hydrogenation (eq 8). ... 

CIC The powerful odour is dominated by 2-isobutyl thiazole and 3-pentanethiol. The green notes are lipid degradation products like (E)-2-hexenal, hexanal and higher unsaturated aldehydes, the pineapple-pear like fruity notes are derived from methyl hexanoate, ethyl-2-hexenoate and hexyl acetate. The spicy cinnamon notes are represented by 3-phenyl propyl acetate, cinnamyl acetate, methyl cinnamate, ethyl cinna-mate and ciimamaldehyde. Gamma-decalactone and 2,5-dimethyl-4-hydroxy-furan-3(2H)-one and 3-hydroxy-2-butanone add the sweet, creamy body. Beta-famesene, citronellol, 2-phenylethanol, beta-ionone add the sweet, floral, quincelike part and methyl benzoate and ethyl benzoate impart a characteristic medicinal, exotic topnote. 

L-Menthol, hydroxy-dihydro-citronellal, d-and L-citronellol Isomerization of allyl amine with Rh-binap >1000 t/y Takasago [5-7]... 

Periodate-Permanganate oxidation [1, 810-812, at end]. In carrying out the oxidation of (R)-(+)-citronellol (8) to the 6-hydroxy-4-methylhexanoic acid (9) by the Lemieux-von Rudloff reagent, Overberger and Kaye16 used acetone-water as the medium in order to conduct the oxidation at a higher concentration. 

Figure 4.1. (Continued) (11) Ho-diendiol I (3,7-dimethyl-l,5-octadiene-3,7-diol) (12) endiol (3,7-dimethyl-l-octene-3,7-diol) (13) Ho-diendiol II (3,7-dimethyl-l,7-octadiene-3,6-diol) (14) citronellol (3,7-dimethyl-6-octen-l-ol) (15) nerol (Z), geraniol (E) (3,7-dimethyl-2,6-octadien-l-ol) (16) neroloxide (17) 2-exo-hydroxy-l,8-cineol (18) 1,8 -cineol (19) wine lactone (20) cis- and /ram-1,8-terpin (21) p-menthenediol I (p-menth-l-ene-7,8-diol) (22) ( )-geranic acid (3,7-dimethyl-2,6-octadienoic acid) (23) (/. )-2,6-dimethyl-6-hydroxyocta-2,7-dicnoic acid (24) (E- and Z)-sobrerol or p-menthenediol II (/>menth-l-ene-6,8-diol) (25) cis- and trans-rose oxide (26) triol (2,6-methyl-7-octene-2,3,6-triol) (27) hotrienol [(5 )-3,7-dimethylocta-l,5,7-trien-3-ol] (28) myrcenol (2-methyl-6-methylene-7-octen-2-ol).

Pure citronellal is a colorless liquid with a refreshing odor, reminiscent of balm mint. Upon catalytic hydrogenation, citronellal yields dihydrocitronellal, citronellol, or dihydrocitronellol, depending on the reaction conditions. Protection of the aldehyde group, followed by addition of water to the double bond in the presence of mineral acids or ion-exchange resins results in formation of 3,7-dimethyl-7-hydroxy-octan-l-al (hydroxydihydrocitronellal). Acid-catalyzed cyclization to iso-pulegol is an important step in the synthesis of (-)-menthol. 

Use C. find use in perfume and soap industries and for the preparation of menthol, citronellol, hydroxy-citronellal, and isopulegol (see p-menthenols). Dog collars impregnated with C. are purported to calm dogs and induce them to bark less. ... 

S)-(-)-p-Citronellol. See (S)-(-)-Citronellol ( )-P-Citronellol. See P-Citronellol Citroneiioi, hydroxy-. See Hydroxycitronellol Citronellonitrile. See Citronellyl nitrile... 

Synonyms Citronellol, hydroxy- 3,7-Dimethyl-7-hydroxy-1 -octanol 3,7-Dimethyloctane-1,7-diol 3,7-Dimethyl-1,7-octanediol 7-Hydroxy-3,7-dimethyloctan-1-ol 1,2-Octanediol, 3,7-dimethyl- 1-Octanol, 3,7-dimethyl-7-hydroxy-Empirical C10H22O2... 

Pseudomonas citronellolis was found to produce mcl-PHA on many different substrates (Choi and Yoon 1994). Similar to P. fluorescens, this strain also produced unsaturated monomers from unrelated C -C acids up to 9 mol% 3-hydroxy-c -5-dodecenoate and up to 2.6 mol% 3-hydroxy-CM-7-tetradecenoate, with the largest content being (7 )-3-hydroxydecanoate. A novel copolyester, poly(3-hydroxy-7-methyl-6-octenoate-co-3-hydroxy-5-methylhexanoate), was synthesized when P. citronellolis was grown on citronellol (Choi and Yoon 1994). 

Maier and Varseev recently applied MacMillan s elegant one-pot three-step protocol 115) (1. a-hydroxylation, 2. Horner-Wadsworth-Emmons HWE) olefination, 3. N—O cleavage) for the conversion of the (5)-citronellol-derived aldehyde 132 to y-hydroxy-a,p-unsaturated ester 133 early in their 18-step first total synthesis of neosymbioimine (134) 116), a minor amphoteric metabolite of the symbiotic marine dinofiagellate Symbiodinium sp. 117) (Scheme 31). 

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