Methyl citronellate

Chlorochroa sayi males produce a pheromone consisting primarily of methyl geranate, with trace amounts of methyl citronellate and methyl dihydrofarnesoate [107]. Methyl geranate is readily available in multigram quantities from fractional distillation of the commercially available mixture of methyl geranate and methyl nerate (J.G. Millar, unpublished data), or the two isomers can be separated chromatographically [107]. 

Die Cyclisierung von optisch aktiven Alkenal-iminen nach diesem Schema kann zur enan-tio- und diastcreoselektiven Synthese von alkyl-substituierten Amino-cyclohexanen herangezogen werden, z. B. von (/ / )-trans-l-Amino-5,5-dimethyl-2-isopropyI-cyclohcxan ausgehend von 3-Methyl-citronellal und (7 )-l-Phenyl-cthyIaminI. 

The analogous cyclization of chiral imines occurs in high yield (75-85 %) with good asymmetric induction (36-65 % ee) [91]. For example, the cyclization of the aldimine derived from methyl citronellal, using SnCU, affords only the tram-substituted amino-cyclohexane in high yield (Eq. 57). exo Products are formed exclusively or preferentially over the thermodynamically favored endo products. 

Methyl 6-hydroxy-3-methylhexanoate is our 1,6-difunctional target molecule. Obvious precursors are cyclohexene and cyclohexadiene derivatives (section 1.14). Another possible starting material, namely citronellal, originates from the "magic box of readily available natural products (C.G. Overberger, 1967, 1968 E.J. Corey, 1968D R.D. Clark, 1976). 

FIGURE 26 8 The distribu tion of the C label in citronellal biosynthesized from acetate in which the methyl carbon was isoto pically enriched with C... 

It contains limoaene, ciiral, citronellal, cioeol, and a little thymol, aa well as other nndetermined phenolic constiments. Unlike other Indian basil oils, it contained no methyl-chavicol. 

Acetate, labeled at either the methyl or carboxyl position, was significantly incorporated into both citronellal and citral. 2-C14-Mevalonate was similarly well incorporated, but, in contrast, 1-C14-mevalonate produced only very slight radioactive labeling in the terpenes. The results of these experiments are summarized in Table I. 

CHROMIUM TRIOXIDE-PYRIDINE COMPLEX, preparation in situ, 55, 84 Chrysene, 58,15, 16 fzans-Cinnamaldehyde, 57, 85 Cinnamaldehyde dimethylacetal, 57, 84 Cinnamyl alcohol, 56,105 58, 9 2-Cinnamylthio-2-thiazoline, 56, 82 Citric acid, 58,43 Citronellal, 58, 107, 112 Cleavage of methyl ethers with iodotri-methylsilane, 59, 35 Cobalt(II) acetylacetonate, 57, 13 Conjugate addition of aryl aldehydes, 59, 53 Copper (I) bromide, 58, 52, 54, 56 59,123 COPPER CATALYZED ARYLATION OF /3-DlCARBONYL COMPOUNDS, 58, 52 Copper (I) chloride, 57, 34 Copper (II) chloride, 56, 10 Copper(I) iodide, 55, 105, 123, 124 Copper(I) oxide, 59, 206 Copper(ll) oxide, 56, 10 Copper salts of carboxylic acids, 59, 127 Copper(l) thiophenoxide, 55, 123 59, 210 Copper(l) trifluoromethanesulfonate, 59, 202... 

Within Hymenoptera, pheromones produced by workers in social colonies are the best studied across many genera, principally in ants [6], with those eliciting trail following most extensively studied. The distinct behavior and the relative ease of the bioassay have resulted in chemical identifications in many species [ 113,114]. Those that have been recently identified are listed in Table 5. In addition, several alarm and recruitment signals have recently been identified. Many of the compounds recently identified in ants have previously been reported as trail or alarm pheromones in other ant species. For example, methyl 4-methylpyrrole-2-carboxylate 64, 3-ethyl-2,5-dimethylpyrazine 65, (9Z)-hexadec-9-enal 66,4-methylheptan-3-ol 67, and methyl 6-methylsalicy-late 68 have been identified as trail pheromone components, and heptan-2-one 69,4-methylheptan-3-one 70, formic acid 71, undecane 61,4-methylheptan-3-ol 67, methyl 6-methylsalicylate 68, and citronellal 72 have been identified as alarm pheromone components [6]. The use of the same chemicals across genera, with some used for very different functions, is an interesting phenomenon. 

The identity of methoprene photoproducts has been studied from aqueous emulsions, thin films on glass or silica gel, and in methanolic solution (Figures 3 and 4, 40). As a thin film (0.1 ym) on glass, the half-life of methoprene was about 6 hr. After 93% degradation of parent, more than 50 photoproducts were observed, only five of these present in 3% or higher yield 7-methoxycitronellic acid (4%), 7-methoxycitronellal (4%), the 4,5-epoxide of methoprene (6%), a C12 methyl ketone (3%), and 14C02 (6%). Similar products were encountered on photolysis of a 100 ppm aqueous emulsion of methoprene, except that methoxy-citronellal was isolated only as its dimethyl acetal (9% yield), a presumed artifact of work-up. In addition to the same products identified from thin film studies, at least forty-six other discrete products were detected, but not identified (40). 

The 1-pro-7 -hydrogen is lost on oxidizing geraniol with a cell-free extract from Cannabis sativa (Vol. 7, p. 9, ref. 96), asymmetric microbial reduction of ( )-citronellal to (-)-citronelloI is reported, and callus cultures of Nicotiana tabacum selectively hydroxylate linalool, dihydrolinalool, and the derived acetates at the -methyl group [e.g. to give (59)]. ... 

The hydrogenation of Claisen rearrangement products (R)-(E)- and (S)-(Z)-3,7-dimethyl-4-octenal [obtained highly selectively from (7 )-( )-6-methyl-4-vinyloxy-2-heptene, see p421] to give (S)- and (7 )-3,7-dimethyloctanal, respectively. Authentic samples of these aldehydes were obtained from (5)- and (7 )-citronellal 14°. 

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. 

Analysis by GC-MS of the contaminating peaks in eluates from a blank control column revealed ethyl hexadecanoate, methylbutyl phthalate, stearic acid, methyl 4-methyldodecanoate, dioctyl phthalate (two peaks), and an alkyl benzene. An eighth peak corresponded to an isomer of geranyl citronellal [(H3C)2C=CHCH2CH2C(CH3)= CHCH2CH2C(CH3)=CHCH2CH2C(CH3)CH2CHO]. The A-162 eluate showed bis(2-ethylhexyl) phthalate. 

Formic (rans-Carveol Citronellal Ethyl acetate Methyl a-p-Copaene... 

Selective hydraformylation of nonconjugated dienes can be carried out such that the least-hindered double bond reacts. Thus citronellene (entry 6) and 2,6-dimethyl-l,5-heptadiene both undergo preferential reaction at the least-substituted double bond, the hydroformylation of citronellene patterned after that of 3-methyl-1-pentene (Table 1) and the hydroformylation of 2,6-dimethyl-l,5-heptadiene to citronellal following that of 2-methyl-1-pentene, avoiding placing the formyl group at the quaternary carbon. The reaction of limonene (entry 8) shows similar behavior. 

Crystallization of the crude material without distillation from tert-butyl methyl ether/hexane affords 56% of rac-5, mp 68-70°C, as pale yellow crystals. The submitters obtained a second crop of 1.5 g from crystallization of distilled material mp 68-78°C, starting from citronellal purchased from BASF. The checkers found that dtronellal from Sigma required distillation and gave an impure second crop of 5 only with difficulty. 

The determination of aldehydes and ketones is of importance in the analysis of those essential oils characterised especially by aldehydic or ketoruc principles, e g.,the citral contained in lemon and lemongrass oils, citronellal in citronella Oil and some eucalyptus oils, benzaldehyde in bitter almond oil, salicylaldehyde in meadow-sweet oil, anisaldehyde in aniseed and fennel oils, cuminaldehyde m cumin oil, cinnamaldehyde in cinnamon oil, carvone in caraway oil, pulegone in pennyroyal oil and methyl nonyl ketone in rue oil The determination of the aldehydes and ketones presents, however, difficulties and the above methods are moderately exact in only a few cases, especially when the content of aldehydes or ketones is considerable The bisulphite method is applicable particularly to the determination of cinnamaldehyde and benzaldehyde in cinnamon oil and bitter almond oil, and, up to a certain pomt, to that of citral in lemongrass Oil. The sulphite method gives good results in the same cases and for the determination of carvone and pulegone... 

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