Isocaryophyllene

This body has been termed by Deussen isocaryophyllene. It yields two nitrosoohlorides, a-isocaryophyllene nitrosochloride melting at 122°, and yS-isooaryophyllene nitrosochloride melting at 146°. 

Boswellia serrata olibanum has a chemical composition close to that of both the B. carteri and of B. sacra, but contains compounds that are absent in those from other Boswellia and could be used as markers methylchavicol (38), p-anisaldehyde (47), methyleugenol (70), isocaryophyllene (82), sesquiterpene 91, elemicin (92) and an unidentified diterpene (124) eluting between cembrene C (123) and verticilla-4(20),7,ll-triene (125). It is devoid of (5-caryophyllene (73), a-humulene (78), caryophyllene oxide (95) and bornyl acetate (50). 

Strategies based on reconnections which have been applied succesfully to sesquiterpenes, such as caryophyllene, isocaryophyllene and hirsutic acid, as well as to Cecropia juvenile hormone. 

Caryophyllenes are a class of sesquiterpenes that protect plants against insects, and have a quite unusual structure a four membered-ring fused to a medium-sized ring of nine carbon atoms. There are two isomers which only differ in the configuration of an endocyclic double bond the so-called a-caryophyllene ( -isomer) (la) and the corresponding (Z)-isomer the P- or isocaryophyllene (lb). 

Therefore, a rational synthesis of caryophyllenes should be designed in such a way that after proceeding through a series of common intermediates at a given step they may offer the opportunity to exert a stereochemical control in the formation of the endocyclic double bond. In this context, the synthesis reported by Corey as early as 1964 [1] is still more efficient than more recent syntheses in which only one isomer (isocaryophyllene, lb) is formed [2] or that require parallel synthetic sequences which start from compounds which are only remotely related to each other [3]. 

The two stereoisomeric 2-alkyl branched 2-alkenyl potassium species obtained upon deprotonation of ( )- and (Z)-isocaryophyllene equilibrate to afford an endo-exo... 

Elegant applications of the contrapolarized orientation in such photocycloadditions include syntheses of caryophyllene/isocaryophyllene [80], 10-epijunenol [191], and helminthosporal [192]. 

Similar observations were made in the dimethylketene adducts of partially resolved cyclonona-1,2-diene and cyclotrideca-1,2-diene (see Table 1). A total synthesis of isocaryophyllene was carried out using the dimethylketene adduct of the partially resolved allene 74 as an intermediate. However, in all of these cases the enantioselectivity of these processes was not determined since the optical purity of the products were not established. 

Double bonds with different geometry behave in a unique way. For example, the monohydroboration of caryophyllene (9) with dicyclohexylborane followed by oxidation brought about the participation of the (E)-trisubstitutcd double bond in preference to the exocyclic double bond during hydroboration to give the corresponding alcohol (10) (Eq. 10)50t. However, under similar conditions, isocaryophyllene (11), which has a (Z)-endocyclic double bond, affords a mixture of unsaturated alcohols... 

This cycloalkanone synthesis furnishes a short synthesis of isocaryophyllene (1), the (Z)-isomer of natural caryophyllene. In this example, the double bond isomerizes during the keto cyclization.2... 

Although isocomene (668), mentioned above, is included in this section it is likely that this hydrocarbon, together with modhephene (679), is derived from a caryophyllene-type precursor. Indeed one can conceive of a biogenetic pathway (Scheme 87) which encompasses both these compounds as well as botrydial (681), quadrone (682), and the recently isolated senoxydene (304). " To lend partial credence to this scheme is the fact that the hydrocarbon (680) is a product of acid-catalysed rearrangement of isocaryophyllene (678). ... 

Direct photolysis of caryophyllene (182) and isocaryophyllene (183) gives rise to an extremely complex mixture of isomeric hydrocarbons. The majority of these have now been identified and rationalizations for their formation have been presented.In addition to the photoisomerization between caryophyllene and isocaryophyllene, caryophyllene produces (184)—(188), whereas isocaryophyllene yields (187)—(192). 

Scheme 5). Similarly, isocaryophyllene (66) undergoes transannular cyclization in mineral acid to (65) and to the tricyclic alkene (67 Scheme 6) in high yield.

An alternative synthesis of ( )-isocaryophylIene (253) has been achieved by the reaction sequence outlined in Scheme 27. ° The conversion of the bicyclic ketone (250) into isocaryophyllene (253) has previously been reported (cf. Vol. 5, p. 67) by another research group. ... 

Cyclization initiation can also be achieved by epoxide ring opening but using this procedure mixtures of products are found28-34. Mixtures of constitutional isomers are observed when naturally occurring caryophyllene or isocaryophyllene are treated with mineral acids 35. 

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