Brown algal polyphenols: synthesis of 'fucophlorethol A' octamethyl ether (2,2′,4,6,6′-pentamethoxy-4′-(2,4,6-trimethoxyphenoxy)biphenyl)

Vanadium tetrachloride-catalyzed dimerization of 3,5-dimethoxyphenol yields the key intermediate 2,2′,6,6′-tetra-methoxy-4,4′-dihydroxybiphenyl, from which the octamethyl ether of the brown algal metabolite "fucophlorethol A" (2,2′,4,6,6′-pentamethoxy-4′-(2,4,6-trimethoxyphenoxy)biphenyl, 6) is synthesized by Ullmann condensation and Hakomori methylation.