Oxygenated p-Menthanes

Both CIS- and trans-p-mentha-l(7),5-dien-2-ol (144) are reported from the essential oil of Cinnamomum japonicum Sieb. and called yabunikkeols (from the Japanese name of the plant) but the structures are unsupported by n.m.r. data. 

Another new aldehyde was recently isolated from the oil of Rosa damascena (Bulgarian rose oil), and shown to be menth-l-en-9-al, a mixture of both diastereo-isomers (152) and (153) being present in the natural product. By oxidation of the hydroboration products of (+)-limonene (111) (see also ref. 109), both 

Ohloff, W. Giersch, K.-H. Schulte-Elte, and E. sz. Kovats, Helv. Chim. Acta, 1969, 52, 1531. 

Katsuhara has discussed the mechanism of opoxidation of endocyclic ocfi-unsaturated terpene ketones and reached the conclusion that the oxygen atom is introduced stereoselectively in such a way that the most favourable transition state involves the best orbital overlap stabilisation. He predicted the formation of lK,4i ,5/ -menth-4-en-3-one epoxide (161) from the unsaturated ketone, a prediction that was subsequently confirmed. 

Some unexpected rearrangements occur when palladium chloride (PdCl2) is allowed to react with allyl alcohols of the p-menthane series in the presence of carbon monoxide. 7t-Allylpalladium compounds are formed, but after 10 days that from piperitol (128) has rearranged to the 3,4,8-tn7iapto-complex (162) which is obtained from pulegol (163) after 1 h. Menth-3-en-2-ol (127) leads to the same complex after 9 days.  

Kayahara, H. Ueda, I. Ichimoto, and C. Tatsumi, Agric. and Biol. Chem. Japan), 1970,34,1597. 

Fujita, S. Fujita, and Y. Hayama, Nippon Nogei Kagaku Kaishi, 1970, 44, 428. 

Albaiges et al. have continued their work on the synthesis of menthenols and menthadienols, preparing menth-3-en-8-ol (126), menth-l(7)-en-8-ol (127), and mentha-l(7),4(8)-dien-9-ol (128). These syntheses involve dehydrating the Reformatsky product (129) obtained from a 4-substituted cyclohexanone (130) and ethyl a-bromoproprionate with phosphorus oxychloride. Conventional treatment of the separated products [(131a), (131b), etc.] leads to the desired substances. 

Coll Toledano, Rev. Real. Acad. Cienc. Exactas, Fis. Natur. Madrid, 1970, 64, 523 Chem. Abs. 1970, 73, 120 761) 

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Oxygenated p-Menthanes. The conformations of dihydrocarvone (148), the diastereoisomeric pairs of the corresponding 1-hydroxy-compound, and some related substances have been studied by temperature-dependent c.d. The conformations of the various stereoisomers (149) of the reduction products of carvotanacetone epoxide, as well as some of the corresponding alcohols from carvone epoxide (150) have been examined through their Hn.m.r. spectra. ... 

The resin secreted by Cannabis indica and Cannabis sativa, varieties of hemp, is known variously as marijuana, hashish or bhang and is abused as a hallucinogenic drug. It appears however to have some beneficial properties and is currently under test as an antiemetic in cancer therapy. The secretion contains a number of interrelated oxygen heterocycles, some of which are shown in Scheme 281, which attempts to indicate their biosynthetic relationships (70MI22401). The cannabinoids are probably derived from a monoterpene unit based on p-menthane and 5-n-pentylresorcinol (olivetol), acting the part of a polyketide. 2,2-Dimethylchromene biosynthesis also requires the intervention of an isoprene fragment. 

Alkanes. In most of the chemical reactions observed in irradiation chambers, saturated hydrocarbons—even highly-branched ones such as p-menthane (l-isopropyl-4-methylcyclohexane)—have been quite unreac-tive. Since attack of alkanes by hydroxyl radical (26), atomic oxygen (27, 28), or ozone (29) follows the C-H reactivity order, tertiary > secondary > primary, the chemical measurements with alkanes would be expected to follow a clear pattern. However some alkanes (e.g., p-menthane) with tertiary hydrogens do not react more rapidly than those (e.g., n-octane) with only secondary and primary hydrogens, and hydrogen abstraction reactions often do not appear to be rate-determining steps. 

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