Carveol epoxide

Other useful p-menthane syntheses of no great novelty are of cis- and trans-piperitol from 2a,3o -epoxycarane (silica-catalysed rearrangement to ds-p-menth-2-en-l,8-diol is also reported), of ( )-dihydrocarvone, isopulegone, and p-menthofuran via /S-keto-sulphoxides, of p-mentha-l,4(8)-diene via a bromination-dehydrobromination sequence, and of trans-carveol by benzoyl peroxide-CuCl oxidation of a-pinene. Further details for the conversion of (-)-(142) into (+)-(142), via its epoxide, are reported (Vol. 5, p. 25 cf. Vol. 3, p. 44). " ... 

As a test reaction a mixture of cis- and trans-carveol was oxidized with TBHP. Analogous to what has previously been observed for compounds like geraniol and linalool, epoxidation was fast and selective (reaction 8). Trans-carveol was converted only to the corresponding epoxide, whereas cis-carveol gave a mixture of cis-epoxide and carvone. 

With VO(HPS)-Y [E] as the catalyst, reaction in the presence of the zeolite gave a much better selectivity towards cis-epoxide, than without zeolite present. This suggests that carveol is able to complex with the vanadium present within the molecular sieve. Moreover, the selectivity on TBHP consumed decreased from 95% to 45%, suggesting that the ligand environment has changed. 

An alternative process for the production of (-)-carvone has recently been elaborated. Starting from (-i-)-limonene 1,2-epoxide, a regioselective rearrangement of the epoxide leads to (-)-carveol (trans- -.[2102-58-1] cis- -.[2102-59-2]). The reaction is effected by the use of a catalyst consisting of a combination of metal salts and phenolic compounds. 

The previously unknown (+ )-(lS,2S,4R)-isodihydrocarveol (157) has been made from (+ )-limonene epoxide (158) as a component of a mixture of isomers, either with lithium in ethylamine or with the stoicheiometric amount of lithium aluminium hydride. Dihydrocarveol (159) has been synthesized from 4-acetyl-1-methylcyclohexene by conventional means.A method that is said to convert allyl alcohols into the corresponding chlorides without allyl rearrangement has been applied to carveol. The chloride was indeed obtained, but since the rotations of the compounds were not recorded it is unfortunately impossible to draw any conclusions about rearrangement. An ingenious synthesis of pure stereoisomers of carvomenthone-9-carboxylic acids involves a [2 -I- 2]-type cycloaddition of an ynamine to 2-methylcyclohex-5-enone (160). This leads... 

In the metabolism of cw-carveol by microorganisms, there are four pathways (pathways 1-4) as shown in Figure 19.86. At rst, cA-carveol (81) is metabolized to carvone (93) by C2 dehydrogenation (Noma, 1977, 1980) (pathway 1). Second, ciY-carveol (81b) is metabolized via epoxide as intermediate to bottrospicatol (92) by rearrangement at C2 and C8 (Noma et al., 1982 Nishimura et al., 1983a,b Noma and Nishimura, 1987) (pathway 2). Third, cA-carveol (81b) is hydroxylated at C5 position to give S-hydroxy-ds-carveol (94) (Noma and Nishimura, 1984) (pathway 3). Finally, cw-carveol... 

---