Urceolatol, a tetracyclic bromobenzaldehyde dimer from Polysiphonia urceolata.

ABSTRACT

Urceolatol (1), a novel bromobenzaldehyde dimer, together with one known bromophenol, 3-bromo-4,5-dihydroxy-benzaldehyde (2), were isolated from the red alga Polysiphonia urceolata. The structure and absolute stereochemistry of 1 were elucidated to be (5R,10R)-2,7-dibromo-3,8-dihydroxy-5,10-dimethoxyl-5,10-dihydrochromeno[5,4,3-cde]chromene, on the basis of spectroscopic techniques and X-ray diffraction analysis.