Caryophyllene alcohol

When caryophyllene alcohol is dehydrated by means of zinc chloride or phosphorus pentoxide, a hydrocarbon results, which does not appear to be identical with any of the sesquiterpenes described under the name caryophyllene. It has therefore been named clovene . Clovene has the following characters —... 

Analysis TM290 was used by Corey ( . Amer. Chem. Soc,, 196, 86, 1652) in his synthesis of a-caryophyllene alcohol. Again, only one disconnection is very productive ... 

Though the rearrangement step transforms a stable tertiary cation into a less stable secondary cation, relief of strain in expansion from a four- to a five-membered ring makes the alkyl migration favourable. In 1964, E.J. Corey published a synthesis of the natural product a-caryophyllene alcohol that made use of a similar ring expansion. Notice the photochemical [2+2] cycloaddition (Chapter 35) in the synthesis of the starting material. 

Other products which were isolated from this study were the related fused 5,7-ring molecules (117)-(119), together with a-caryophyllene alcohol (116 Scheme 13). 

The ready availability of four-membered rings of defined stereochemistry from enone-alkene photocycloadditions has been the origin of several syntheses which employ Wagner-Meerwein rearrangements in subsequent steps. This is exemplified by a neat and very short synthesis of a-caryophyllene alcohol (40) from cyclopentene and 3-methylcyclohexenone which was described some years ago (see Scheme 15). The rearrangement in 40% sulfuric acid proceeded remarkably smoothly. A short synthesis of iso-comene (41 Scheme 16) also Illustrates this strategy... 

These compounds co-occur in the essential oil of Cedrus atlantica and it is interesting to note that a-caryophyllene alcohol (62) (obtained for the first time as a natural product) and the epimeric himachalene epoxides (63 a and b) have also been identified as co-metabolites. ... 

Normally 1,1-disubstituted double bonds react faster with protons than do 1,1,2-trisubstituted ones because the former are more polarisable, a feature which protons prefer. However, in the case of caryophyllene, the endocyclic trans double bond is so strained that the normal reactivity pattern is reversed and it is this bond which is protonated first. In Figure 7.35, protonation of the endocyclic double bond is rapidly followed by addition of the electrons of the exocyclic bond to give the tricyclic carbocation (7.164). As would be expected, in both instances, the electrophile is added to the less substituted end of the olefin. The carbocation can be trapped by water to give the alcohol (7.165) which is known both as caryophyllene alcohol and caryolanol. Alternatively, a 1,2-carbon shift can occur to reduce strain... 

This ring-expansion process is quite useful when applied to polycyclic systems. Corey treated 57 with 40% sulfuric acid and isolated the rearranged alcohol, a-caryophyllene alcohol (60). The initially formed cyclo-butylcarbinyl cation (58) rearranged to the cyclopentyl cation (59), which was trapped by water to give 60. 

Synonyms a-Caryophyllene alcohol Decahydro-2,2,4,8-tetramethyl-4,8-methanoazulen-9-ol... 

Synonyms Caryophyllene acetate p-Caryophyllene alcohol acetate 4,11,11-Trimethyl-8-methylenebicyclo [7.2.0] undec-3-en-5-yl acetate... 

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