Tetraprenyltoluquinols from the brown alga Cystophora fibrosa

Enantiomeric 4′-methoxyamentol, a tetracyclic tetraprenyltoluquinol, has been isolated from the South African marine brown alga Cystophora fibrosa as well as another five amentol derivatives with a further five stereoisomers. The stereochemistry of these compounds is discussed in relation to the results of a series of molecular modelling experiments.