Piperitone

An optically active, secondary terpene alcohol. ( —)-Piperilol is found in various eucalyptus oils and (-l-) piperitol in the oil from a species of Andropogon. A somewhat viscous oil of pleasant smell. It yields piperitone on oxidation with chromic acid. 

Piperitone is of considerable technical im portance. It is a colourless oil of a pleasant peppermint-like smell. (-)-Piperilone has b.p. 109-5-110-5 C/I5mm. Piperitone yields thymol on oxidation with FeCl. On reduction with hydrogen in presence of a nickel catalyst it yields menthone. On reduction with sodium in alcoholic solution all forms of piperitone yield racemic menthols and womenthols together with some racemic a-phel)andrene. 

The final condensation could haye gone the other way too, but it doesn t, presumably because attack on, the other carbonyl group is hindered. TM 120 is in fact piperitone, one of the flayouring principles of mint, and has been synthesised essentially by this route g.C.S... 1935, 1583 Rec. Tray. Ctum.. 1964, 464 Zhur. Obshchei Khim.. 1964, 34=... 

Thia true is fcha Bastard Stringy Bark of New Soulh Wales. Tha oil eontaiua eucalyptol, piperitone, and eudeamol, with a large amoont of phellandrene, and haa the followuig charaetera —... 

It coDtaina phellandrene, i.ucalt ptol, a sesquiterpene, piperitone, and citral... 

Piperitol is a secondary alcohol, corresponding with the ketone, piperitone, occurring in several of the so-called peppermint group of eucalyptus oils. ... 

Piperitone can be most easily obtained from the higher boiling portions of the oil of E. dives. It combines slowly with sodium-bisulphite, and by repeated agitation for two or three weeks eventually forms crystals in some quantity. A proportion of alcohol assists the combination. The pure ketone prepared from the purified crystals is colourless at first, but on long standing becomes slightly yellowish in tint. It has a burning peppermint-like taste and odour. The formula is... 

According to Read and Smith i piperitone is, under natural conditions, optically inactive. By fractional distillation under reduced pressure, it is prepared, by means of its sodium bisulphite compound, in a laavo-rotatory form. The slight laevo-rotation is probably due to the presence of traces of cryptal. By fractional distillation alone, it is usually obtained in a laevo-rotatory form whether this is due to decomposition products or not is unknown. Piperitone has a considerable prospective economic value, as it forms thymol by treatment with formic chloride, inactive menthone by reduction when a nickel catalyst is employed, and inactive menthol by further reduction. Its char-Mters are as follows —... 

Givaudan Co., however, compare the properties of piperitone with those of the ketone prepared synthetically by Wallach, and discovered in Japanese peppermint oil by Schimmel and later in camphor oil by Bchimmel, and finally in the oil of Cymhopogon sennaarensis by Roberts,"... 

Read and Smith loc. cit.) have prepared benzylidene-piperitone, of the formula CioHi O CH. CgHg, by the interaction of piperitone and benzaldehyde in the presence of alcoholic sodium ethoxide. This body melts at 61°, and the discoverers claim that it is sufficiently characteristic to definitely differentiate piperitone from any of the hitherto described menthenones. 

Menthone can be prepared by the reduction of piperitone. For this. Smith and Penfold give the following method —... 

Pure piperitone was subjected to the action of purified hydrogen, in the presence of a nickel catalyst, for six hours, the temperature ranging between 175° to 180° C. The double bond in piperitone was readily opened out with the formation of menthone, but further action of the hydrogen under these conditions did not reduce the carbonyl group, even after continued treatment for two days. Under correct conditions, however, the reduction to menthol should take place. The ease with which menthone is formed in this way is of special interest, not only in connection with the production of this ketone, but also as a stage in the manufacture of menthol. 

The reduction of piperitone to menthone cannot well be brought about by the action of sodium or of sodium-amalgam in alcoholic solution, because, with the latter particularly, a solid bimolecular ketone is formed at once. This is a finely crystallised substance, melts at 148° to 149° C., and has the formula C gHj O. Piperitone thus follows the rule with substances having a conjugated double bond, carvone for instance, also forms a bimolecular ketone on reduction, melting at 148° to 149° C. 

Menthone was prepared from piperitone in almost quantitative yield, and had the characteristic peppermint odour of this substance. It. 

Smith and Penfold have shown that thymol can be prepared by the action of-ferric chloride on piperitone. 

The photocycloaddition of an excess of cyclobutenecarboxylic acid (380) and (—)-piperitone (381), followed by esterification with diazomethane, gave the adduct (382). Reduction of (382) afforded the lactone (383). Upon thermolysis in decane at 174 °C, the lactone (383) was converted to the dihydroisoaristolactone (384). Thermolysis of (382) in refluxing decane gave quantitative yield of the compound... 

There are ample evidences which suggest that a cyclic periodate ester is the intermediate 148). Cyclobutane-1,2-diols can also be cleaved oxidatively and this aspect has been used in organic synthesis. Thus, photocycloaddition of l,2-bis(tri-methylsiloxy)cyclobutene to (—)piperitone (381) gave the photoadduct (438). Desilyla-... 

Piperitone, Z-menthol from, 24 522—523 Pipe still furnaces, 18 646 Pipe taps, 11 658-659 Piping... 

Piperitone, with its fresh minty camphor4ike odor, is present in various leaf essential oils. Among Mentha and Eucalyptus genera, there are piperi tone-rich species which are considered common sources of this natural monoterpene ketone. The (45) (-f)- enantiomer was reported to be... 

The two diastereomers of cis- and rmws-piperitone oxide are 1,2-epoxy-3-keto-p-menthanes, which have been found in various plant species. The most abundant natural sources of these compounds are plants belonging to the Lamiaceae family, especially Mentha and Calamintha In many publications, the authors gave no details on the diastereomeric composition of piperitone oxides, probably because of their very similar retention times on a non-polar column. 

S,2S,AS) —)-trans-V vpcntonc oxide (dihydro rotundifolone) has been isolated for the first time from Mentha longifolia by Reitsema and Varnis. The presence of the (15,25,4i )(—l-ar-isomer was reported in aAf. spicata mutant. Only enantiomerically pure levorotatory piperitone oxides, (15,25, AS)-trans piperitone oxide and (15,25, AR)-cis piperitone oxide, were detected by chiral GC analysis of Micromeria fruticosa and Mentha longifolia The occurrence of the cis- and trans- piperitone oxides was dependent on the population of the species. In most cases, the enantiomeric composition of trans- and cis- piperitone oxides detected in various essential oils is unknown. 

The antimicrobial activity of piperitone oxide rich Mentha rotundifolia M. suaveolens) oil was investigated by Oumzil et al., who found it less significant than that of pulegone or piperitone rich oils. The biosynthesis of the two levorotatory diastereomers from (15,25)(+)-piperitenone oxide... 

Larkov O, Matasyoh JC, Dudai N, Lewinsohn E, Mayer AA, Ravid U, Distribution of piperitone oxide stereoisomers in Mentha and Micromeria species and their chemical syntheses. Flavour Fragr/22 328—333, 2007. 

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