Polyhydroxy biphenyl ethers from the brown alga Cystophora congesta

Abstract

Two new phloroglucinol polymers have been isolated from the aqueous extract of the brown alga Cystophora congesta. They are the linear trimer 2,2',4,6,6'-pentahydroxy-1'-(3,5-dihydroxyphenoxy)- biphenyl ether (1)* and the isomeric angular trimer 3,4',5,6'- or 3,3',5,5'-tetrahydroxy-2'-(3,4,5-tri-hydroxyphenoxy)biphenyl ether which was characterized as its heptaacetoxy derivative (4). Structures were elucidated principally from an analysis of 13C n.m.r. chemical shifts and 13C-1H spin-spin coupling data. X-ray analysis was performed on the heptaacetoxy derivative of (1) to distinguish it from a regio-isomer (3).