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The asymmetric synthesis of a triene C18 : 3 n‐8 methoxylated ether lipid (MEL) of the 1‐O‐alkyl‐sn‐glycerol type is described by two different routes. The C18 : 3 hydrocarbon chain is attached by an ether linkage to the pro‐S hydroxymethyl group of the glycerol backbone, and constitutes an all‐cis methylene skipped triene framework, along with a methoxyl group in the 2'‐position and R‐configuration at the resulting chiral centre. The initial synthesis was based on the polyacetylene approach involving a semi‐hydrogenation of the resulting triyne. A modified approach based on a combined polyacetylene‐Wittig strategy was also successfully executed and an attempt made to compare and evaluate these strategies. Both syntheses were started from our previously described enantio‐ and diastereomerically pure isopropylidene‐protected glyceryl glycidyl ether, a double‐C3 building block designed as a head group synthon for synthesis of various types of MELs which was shown to suit the Wittig‐based approach very well. [ABSTRACT FROM AUTHOR]

This report describes synthesis of novel structured triacylglycerols (TAGs) and diacylglyceryl ethers (DAGEs) of the 1- O-alkyl- sn-glycerol type constituting EPA and DHA as the sole fatty acids. One of two TAGs was comprised of a pure EPA located at the 1,3-positions with pure DHA at the 2-position and the other had it reversed with a pure DHA at the 1,3-positions and pure EPA at the 2-positions. The similarly structured DAGEs were derived from chimyl-, batyl-, and selachyl alcohols constituting pure EPA at their sn-3 position with pure DHA at the sn-2 position as well as the opposite composition with pure DHA at the sn-3 position and EPA at the sn-2 position, the total of six such DAGE products. The syntheses of these compounds were brought about by a two-step chemoenzymatic process involving a highly regioselective immobilized Candida antarctica lipase to incorporate EPA or DHA activated as acetoxime esters exclusively into the 1,3-positions of glycerol and the sn-3 position of the 1- O-alkyl- sn-glycerols. The second PUFA acyl groups were subsequently introduced to the remaining 2-positions by EDCI coupling agent to accomplish the title compounds highly efficiently in very high to excellent yields (86-92%). Practical applications: The work described is based on a previously reported methodology to introduce n-3 PUFAs activated as oxime esters exclusively into the terminal 1,3-positions of glycerol and 1- O-alkyl- sn-glycerols to prepare reversed structured TAGs and DAGEs by use of immobilized Candida antarctica lipase. The methodology is ideal for introducing isotopically labeled fatty acids into predetermined positions of TAGs and DAGEs. Novel structured triacylglycerols (TAGs) and diacylglyceryl ethers (DAGEs), constituting EPA and DHA as the sole fatty acids, were obtained by a two-step chemoenzymatic synthesis comprised of an exclusive incorporation of EPA or DHA, activated as acetoxime esters, into the terminal positions of glycerol and 1- O-alkyl- sn-glycerols by use of immobilized Candida antarctica lipase, and a subsequent introduction of a second PUFA acyl group to the remaining 2-positions by EDCI coupling agent. [ABSTRACT FROM AUTHOR]

This paper focuses on a detailed evaluation of commercially available immobilized lipases and simple monohydric alcohols for the production of alkyl esters from sunflower oil by enzymatic alcoholysis. Six lipases were tested with seven alcohols, including straight and branched-chain primary and secondary alcohols. The reactions were conducted in a batch stirred reaction vessel using stoichiometric amounts of substrafes under solvent-free conditions. Dramatic differences in alcoholysis performance were observed among the different lipases. For most of the alcohols, Novozym 435 produced the highest yield of FA alkyl esters, with yields well over 90% for methanol, absolute ethanol, and 1-propanol. Overall, 96% ethanol was the preferred alcohol for all lipases except Novozym 435, and ethanolysis reactions reached the maximal conversion efficiency. Increasing the water content in the system resulted in an increased degree of conversion for all lipases except Novozym 435. The secondary alcohol 2-propanol significantly reduced the alcoholysis reaction with all lipases; however, the branch-chain isobutanol was more advantageous than linear 1-butanol for Novozym 435, Lipozyme RM IM, and Lipase PS-C. Many commercial immobilized lipases are highly efficient and promising for the production of alkyl esters, offering high reaction yields and a simple operation process. [ABSTRACT FROM AUTHOR]

The objective of the work described in this paper was to study a possible FA selectivity of digestive lipolytic enzymes isolated from salmon and trout intestines toward astaxanthin diesters of various FA composition and compare it with the FA selectivity of microbial lipase. Astaxanthin diesters of varying FA composition were prepared in excellent yields (>90%) by chemical esterification using a carbodiimide coupling agent. The astaxanthin diesters were screened in a hydrolysis reaction by various commercially available lipases. The highest conversion rates were observed with the Candida rugosa lipase, which discriminated against n-3 PUFA. The rate of hydrolysis was determined by HPLC. Digestive lipolytic enzymes isolated from salmon and rainbow trout intestines displayed reversed FA selectivity. Thus, astaxanthin diesters highly enriched with n-3 PUFA including EPA and DHA were observed to be hydrolyzed at a considerably higher rate than the more saturated esters. Similar trends in FA selectivity were observed in the hydrolysis of fish oil TAG by the digestive lipolytic enzyme mixtures. [ABSTRACT FROM AUTHOR]