Cyclofarnesanes

A detailed account of the chemical and spectroscopic evidence for the structures of cochlioquinone-A (18a) and -B (18b) has been published. These compounds are metabolites of Cochliobolus miyabeanus, a parasitic mould which grows on rice, and their unusual cyclofarnesane structure is probably derived in nature by introduction of a farnesyl unit into an aromatic precursor followed by cyclization of an intermediate bis-epoxide. 

Apart from a few compounds isolated from aquatic plants 543, 604, 652), sesquiterpene derivatives with a reduced carotenoid structure [mono-cyclofarnesane (555)] have not been detected in terrestrial plants. Thus, 9-vinyl-7,8-dihydro-a-ionol is still a synthetic product which, however, shows a biogenetic relationship to the ethers of the caparrapi series (210)/(211) 348). 

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