.
Angewandte
Communications
decane-1,17-diol. These molecules are based on a C16 building
block (palmitoleic acid) which is a major component of algae
oils but not of traditional plant oils. a,w-Difunctional com-
pounds can be obtained in high purity, even enabling step-
growth polycondensation to a high molecular weight polyes-
ter. This novel polyester possesses an advantageously high
melting point as a result of the crystallizable linear segments
originating from the algae oil lipids.
Notably, the transition metal catalyzed methoxycarbony-
lation is possible on the crude algae extract. Neither the five-
fold unsaturated eicosapentaenoic acid nor other non-fatty
acid components of the algae (amongst others phosphocho-
lines, see Figure 1) shut down catalysis. While an optimization
of the work-up procedures for larger scale synthesis was not
a focus of this work, it can be noted that already at this stage
a complicated chromatographic workup of the catalysis
products is not necessary. Instead, a recrystallization was
sufficient, which can be readily scaled.
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A detailed investigation on different algae strains—
including genetic modification—for the production of fatty
acids, alternative extraction methods, and the conversion by
other synthetic methods are part of our ongoing research in
this topic.
Experimental Section
Detailed procedures and characterization of monomers and polymers
(including NMR spectra, GC-, SEC- and DSC-traces, and WAXS) are
given in the Supporting Information.
Growth of algae: Phaeodactylum tricornutum UTEX 646 was
obtained from the Culture Collection of Algae at the University of
Texas in Austin and grown in 10 L flasks in a modified f/2-
medium[35,36] (pH 7) with artificial half concentrated sea salts
(16.6 gLÀ1, tropic marine) and 0.09 mm MnCl2 at a light intensity of
35 mmolsÀ1 mÀ2 in a day/night rhythm of 16/8 h at 208C. Ambient air
was bubbled through the flasks. The algae were cultivated for 7–
8 weeks, being in the stationary phase for at least six weeks.
Centrifugation of 30 L algae culture yielded 45.3 g of fresh weight
algae, after freeze drying 12.8 g of dry weight algae were obtained.
Work-up by ultrasonication, acidic hydrolysis, and solvent extraction
yielded 5.8 g of crude algae oil, which was directly subjected to
isomerizing methoxycarbonylation.
Isomerizing methoxycarbonylation: Crude algae oil (5.8 g) and
the catalyst precursor [(dtbpx)Pd(OTf)](OTf) (0.97 mmol), or 1,2-
dioleoyl-sn-glycero-3-phosphocholine (450 mg, 0.57 mmol) and the
catalyst precursor (0.009 mmol), respectively, were dissolved in
methanol. In a pressure reactor, the solution was pressurized with
20 bar CO and heated under stirring to 908C for seven days. The
resulting suspension was diluted with methylene chloride and filtered
to remove solids. The solvents were evaporated, and the crude
product mixture was analyzed by GC. Recrystallization yielded 2.1 g
and 320 mg of the desired linear diesters, respectively.
Polymerization of algae oil monomers: Stoichiometric amounts
of the algae oil-based linear diester and diol mixtures were mixed in
a mechanically stirred Schlenk tube. Titanium(IV) tetrabutoxide was
added as catalyst and the mixture was heated stepwise to 2008C under
reduced pressure to yield the algae oil-based polyester.
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[23] Common nomenclature of fatty acids gives the number of carbon
atoms in the fatty acid chain and the number of double bonds.
Received: April 4, 2014
Published online: && &&, &&&&
Keywords: algae oil · catalysis · polyester · renewable resources
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ꢀ 2014 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Angew. Chem. Int. Ed. 2014, 53, 1 – 6
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