Carvone transformation

Where multiple products are possible, the CMR and MBR have been employed to optimize conditions for formation of specific components of a reaction sequence. Examples discussed below, were obtained by heating organic substrates such as allyl phenyl ether [46] and carvone [47] in water. Rearrangements, addition or elimination of water and isomerizations occurred, with each transformation favored under tightly defined conditions. 

A total synthesis of functionalized 8,14-seco steroids with five- and six-membered D rings has been developed (467). The synthesis is based on the transformation of (S)-carvone into a steroidal AB ring moiety with a side chain at C(9), which allows the creation of a nitrile oxide at this position. The nitrile oxides are coupled with cyclic enones or enol derivatives of 1,3-diketones, and reductive cleavage of the obtained cycloadducts give the desired products. The formation of a twelve-membered ring compound has been reported in the cycloaddition of one of the nitrile oxides with cyclopentenone and as the result of an intramolecular ene reaction, followed by retro-aldol reaction. 

Limonene (92) is the most widely distributed terpene in nature after a-pinene [68]. The (+)-isomer is present in Citrus peel oils at a concentration of over 90% a low concentration of the (-)-isomer is found in oils from the Mentha species and conifers [26]. The first data on the microbial transformation of limonene date back to the sixties. A soil Pseudomonad was isolated by enrichment culture technique on limonene as the sole source of carbon [69]. This Pseudomonad was also capable of growing on a-pinene, / -pinene, 1-p-menthene and p-cymene. The optimal level of limonene for growth was 0.3-0.6% (v/v) although no toxicity was observed at 2% levels. Fermentation of limonene by this bacterium in a mineral-salts medium resulted in the formation of a large number of neutral and acidic products. Dihydrocarvone, carvone, carveol, 8-p-menthene-1,2-cw-diol, 8-p-menthen-1 -ol-2-one, 8-p-menthene-1,2-trans-diol and 1 -p-menthene-6,9-diol were among the neutral products isolated and identified. The acidic compounds isolated and identified were perillic acid, /Msopropenyl pimelic acid, 2-hydroxy-8-p-menthen-7-oic acid and... 

The fungal bioconversion of limonene was further studied [82]. Penicillium sp. cultures were isolated from rotting orange rind that utilised limonene and converted it rapidly to a-terpineol. Bowen [83] isolated two common citrus moulds, Penicillium italicum and P. digitatum, responsible for the postharvest diseases of citrus fruits. Fermentation of P. italicum on limonene yielded cis- and frans-carveol (93) (26%) as main products, together with cis- and from-p-mentha-2,8-dien-l-ol (110) (18%), (+)-carvone (94) (6%), p-mentha-1,8-dien-4-ol (111) (4%), perillyl alcohol (100) (3%), p-menth-8-ene-1,2-diol (98) (3%), Fig. (17). Conversion by P. digitatum yielded the same products in lower yields. The two alcohols />-mentha-2,8-dien-1 -ol (110) and p-mentha-1,8-dien-4-ol (111) were not described in the transformation studies where soil Pseudomonads were used [69]. 

X-ray analysis of hydrindanone 29 showed a cis ring fusion. The absolute configuration of 29 was proposed by applying the octant rule109. The absolute configuration of the transfused hydrindanone 30 was correlated by chemical transformations of (—)-carvone. The ketone 30 CD is in accord with the octant rule110. 

Scheme 28 Transformation of ( R)-carvone oxide into a fischerindole precursor...

To achieve this goal, (—)-carvone was transformed into the dimethylhydrazone, and the unsaturated hydrazone was deprotonated by EDA (Scheme 37). Due to complexation of the lithium ion with nitrogen, 3,3-dimethoxypropyl bromide was used to alkylate the a-position (202). A 3 2 mixture of the two possible stereoisomers 332 and 333 was obtained. The authors claimed that the ketone was... 

Stypodiol, epistypodiol and stypotriol are secondary diterpene metabolites produced by the tropical brown algae Stypopodium zonaie. These compounds display diverse biological properties, including strong toxic, narcotic, and hyperactive effects upon the reef-dwelling fish. In the laboratory of A. Abad an efficient stereoselective synthesis of stypodiol and its C14 epimer, epistypodiol, was accomplished from (S)-(+)-carvone. The key transformations in the synthesis of these epimeric compounds were an intramolecular Diels-Alder reaction, a sonochemical Barbier reaction and an acid-catalyzed quinol-tertiary alcohol cyclization. 

Regiosp>ecific synthesis of enol silyl ethers can also be achieved from enones either by reductive silylation or by 1,4-addition of the conjugated system. Thus, Li/NH reduction of the decalone (27) and silylation give the enol silyl ether (28). Similarly, addition of lithium dimethylcuprate to cyclohexenone followed by silylation gives the enol silyl ether (29). Trimethylsilyl cyanide (30) normally adds 1,2 to conjugated ketones (e.g. carvone, 31). However, in the presence of trialkylaluminum, 1,4-addition bdces place to give the enol silyl ether (32 Scheme 9). The same overall transformation can be accomplished by diethylaluminum cyanide and trimethylchlorosilane. ... 

Flavor of Microbial Transformation Products. The flavor of terpenoids produced by microbial transformation was evaluated. (-)-Carvone (1) is well known as a spearmint flavor component. Transformation products (4 - 7) of 1 had peppermint-like flavor although these are slightly different to each other in terms of the odor quality. The metabolites, bottrospicatols (10a and 10b) Streptomyces species did not have a characteristic flavor but quite different activities (Figure 8). (+)-Bottrospicatal (15) which was produced by the oxidative reaction of (+)-bottrospicatol (10a) with CrOa in pyridine had a weak spice-flavor (slightly black-pepper like). The ester derivatives (13 in Figure 7) had a weak medicinal flavor. The flavor of acetyl ester (13a) was the strongest of all. 

The aldehyde has been prepared [165] from (-)-carvone, which was epoxydized and transformed into (+)- ram,-carveol. Orthoacetate Claisen rearrangement and saponification afforded the corresponding y,5-... 

Scheme 6 Transformation of Carvone (71) to methyl ketone (74) was achieved by the use of known reagents. It was converted to a mixture of diasteromers(75) and separarated. Hydration of each isomer with dilute methanolic oxalic acid yielded the corresponding lactone (76), each of which was converted into the same lactone (77). Epoxidation followed by reduction gave a mixture of epimeric diols whose diacetate was subjected to pyrolysis to phytuberin (55).

Hydroxyketone (72) (Scheme 6) prepared from R-carvone, was made to react with dichloromethyl lithium to yield (94) in 9 1% yield and this upon treatment with potassium carbonate in anhydrous ethanol yielded hemiacetal (95) in 75% yield. Its conversion to ester (96) was achieved by oxidation and then acetylation. This upon treatment with LDA at -78°C afforded lactone (97) whose structure was confirmed by X ray diffraction. Subjection to dehydration and cuprate addition provided compound (98) whose transformation to phytuberin has been discussed by Findlay.44... 

X-ray emission analysis of platinum-gold catalysts bears out that gold decorates the platinum particles rims pointing out that low coordination platinum atoms which are selectively deactivated by gold deposition, are responsible for the direct transformation of carvone into carvomenthone. 

Many syntheses of tropanes proceed by nucleophilic addition of amines to cyclohepta-2,6-dienones. A variation of this method, by starting with a substituted cyclohexenone, permits the synthesis of novel tropanes. Such a transformation of carvone (50) is shown in Scheme 10. 

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