Polyhydroxy biphenyl ethers from the brown alga Cystophora congesta

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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).