Phenolic ether lipids with an n-alkenylresorcinol moiety from a bolivian strain of Botryococcus braunii (A race)

Abstract

Eight series of phenolic ether lipids have been isolated from a Bolivian strain of Botryococcus braunii (A race). The lipids constitute, as a whole, up to 34% of the dry biomass. They are structurally related to a homologous series of three long chain n-alkenylresorcinols with C 25, C 27 (major) and C 29 hydrocarbon chains, and, a minor series of n-alkenylresorcinol dimethyl ethers excepted, to hydrocarbons e.g. C 27 dienes and tetraenes previously identified in this strain. The above structures were determined by spectroscopic analyses and chemical degradations involving oxidation and ether cleavage. With the exception of the dimethyl ethers, these lipids exhibit one or two ether bridges binding, on the one hand, the resorcinol nucleus, and on the other a C 27 alkatrienyl chain and/or a C 27 alkenyl one. The latter can, in turn be ether-linked to an alkatrienyl chain, thus resulting in the formation of high M r ether lipids. Moreover, one of these phenolic ethers was found to result from a C-alkylation of the aromatic nucleus. On structural grounds, a biogenetic relationship is proposed between these unusual ether lipids, with the monoepoxides derived from C 27 dienes and C 27 tetraenes as possible intermediates in the O- and C-alkylation pathways of the resorcinol nucleus.