P. Metzger, PHENOLIC ETHER LIPIDS WITH AN N-ALKENYLRESORCINOL MOIETY FROM A BOLIVIAN STRAIN OF BOTRYOCOCCUS-BRAUNII (A-RACE), Phytochemistry, 36(1), 1994, pp. 195-212
Eight series of phenolic ether lipids have been isolated from a Bolivi
an strain of Botryococcus braunii (A race). The lipids constitute, as
a whole, up to 34% of the dry biomass. They are structurally related t
o 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 degr
adations involving oxidation and ether cleavage. With the exception of
the dimethyl ethers, these lipids exhibit one or two ether bridges bi
nding, on the one hand, the resorcinol nucleus, and on the other a C-2
7 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 format
ion 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 st
ructural grounds, a biogenetic relationship is proposed between these
unusual ether lipids, with the monoepoxides derived from C-27 dienes a
nd C-27 tetraenes as possible intermediates in thetetraenes as possibl
e intermediates in the O- and C-alkylation pathways of the resorcinol
nucleus.