Conioids Norlignans , Including Condensed and Structurally Related Compounds

3 Conioids (Norlignans), Including Condensed and Structurally Related Compounds 

Sequirin D (19) from Sequoia sempervirens (12, 54) and yateresinol (20) of Libocedrus yateensis (41) are two compounds that may be mentioned in this context although they do not possess the characteristic C17 backbone of the conioids. A diphenylbutadiene (21) has also been isolated from the heartwood of L, yateensis (41). Possible biogenetic relationships between the common lignans, yateresinol (20), the conioids, and the diphenylbutadiene (21) have been discussed by Erdtman and co-workers (41) and by Whiting (121). 

The lability of several conioids suggests that natural oligomers and polymers may occur. Polymerization of sequirin under acidic conditions results in a material having an infrared spectrum nearly identical with that of the water-soluble polymers ( tannin and phlobaphen ) from redwood (Sequoia sempervirens) (93). Milder acid treatment of sequirin and also of hydroxysugiresinol yields isose-quirin, the structure of which has been postulated mainly on the basis of a mechanism of its formation (93). 

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