Neoisostegane, a New Bisbenzocyclooctadiene Lignan Lactone from Steganotaenia araliacea

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Abstract
Neoisostegane, the first naturally occurring steganin without a functional group at C-5, was isolated from 2 different collections of Steganotaenia araliacea. The structure of neoisostegane, which contained 5 aromatic methoxyl groups rather than the more usual 3 methoxyls and one methylenedioxy moiety, was elucidated by comparison of the PMR coupling constants with those of synthetic steganes and by selective decoupling experiments. The structure was confirmed by cmr [carbon magnetic resonance] data, by preparation of a derivative having 5 aromatic methoxyl moieties from stegane, which was compared spectroscopically to neoisostegane, and by thermal isomerization experiments.