Synthesis of polyfunctional glycerol esters: Lipase‐Catalyzed esterification of glycerol with diesters

Abstract

The enzymatic esterification of glycerol with dicarboxylic acids or esters was studied to produce mono-and/or diesterified glycerol adducts. Such materials are useful synthons in the synthesis of biodegradable polymers and surfactants. In this work two strategies were studied for preparing these prepolymeric glycerol derivatives: the lipase-catalyzed esterification of free glycerol with diacids or esters and the reaction of supported or protected glycerol with diesters. For example, reaction of isopropylidene glycerol with dimethyl sebacate gave a >95% yield of isopropylidene glycerol-monomethyl sebacate ester. Reaction of glycerol supported on silica with dimethyl adipate gave a 40% yield of glycerol-monomethyl adipate ester. Best yields of glycerol-mono-and diesters (70% and 10%, respectively) were obtained by direct esterification of free glycerol with a diester in a solvent-free system containing small amounts of water (<4%). JAOCS 75, 1545-1549 (1998).The lipase-catalyzed esterification of aliphatic dicarboxylic acids with diols has been studied extensively for the production of bifunctional precursors in the synthesis of biodegradable polymers (1-3). In this regard, the enzymatic esterification of glycerol with diacids also would be attractive (Scheme 1). The latter reaction should result in the formation of monoand/or diesterified glycerol products that can be used as trifunctional synthons in the synthesis of glycerol-derived biopolymers or surfactants. The synthesis of such partial glycerides can be achieved using either chemical or enzymatic methods (4). Chemical methods typically are carried out with inorganic catalysts at high pressure and temperature and suffer several drawbacks such as low yields, unwanted side reactions, and decomposition products that result in discolored reaction products. Enzymes (lipases), on the other hand, operate under milder conditions and hence offer advantages over chemical methods. Basically, three strategies have been used in the lipase-catalyzed synthesis of partial glycerides: (i) partial hydrolysis of triacylglycerols; (ii) glycerolysis of triacylglycerols; and (iii) direct esterification of glycerol with acyl donors. The latter strategy, however, deals with substrates that often have very different solubility characteristics, which often inhibits their reaction with each other. A number of publications have addressed this problem by devising different methods to modify the solubility of glycerol, for example by adsorption onto inert supports (5-7), use of the isopropylidene protecting group (8-10), or complexation with phenyl boronic acid (PBA) (11,12). Other approaches to overcoming the glycerol solubility limitation include carrying out the reaction with substrates in biphasic systems (13), by microemulsion (14), or by addition of water to the reaction media (15). One objective of our present study is the synthesis of polyfunctional glycerol esters of dicarboxylic acids for use as prepolymeric synthons. Attempts to prepare these synthons using the above enzymatic ...

Lewis Acid‐Catalyzed Synthesis of Hyperbranched Polymers Based on Glycerol and Diacids in Toluene

“…Our research group has explored the direct utilization of refined glycerol to produce mono-and diesterified adducts [1] and hyperbranched polyesters [2,3]. Identifying new uses for glycerol would be of great benefit to the biodiesel industry because glycerol is the principle coproduct made from the transesterification process by which biodiesel is produced.…”

Plant lipases: Biocatalyst aqueous environment in relation to optimal catalytic activity in lipase‐catalyzed synthesis reactions

“…Thus, the importance of the water content of the system was shown (Green and Nakajima, 1998;Haraldsson and Thorarensen, 1999;McNeill and Sonnet, 1995;Rosu et al, 1999;Villeneuve et al, 1998). Some studies reported that the water thermodynamic activity (a w ) is conditioning the lipase spatial structure and thus its enzymatic activity either toward synthesis or hydrolysis (Chandler et al, 1998;Soumanou et al, 1998b;Svensson et al, 1994;Valivety et al, 1992Valivety et al, , 1994Villeneuve et al, 1997a;Lee and Foglia, 2000).…”

Solvent‐free lipase‐catalyzed thioesterification and transthioesterification of fatty acids and fatty acid esters with alkanethiols in Vacuo

“…To our knowledge the vacuum conditions reported here were being used for the first time in thioesterification and transthioesterification reactions with lipases. However, other lipase-catalyzed esterifications and transesterifications in vacuo are well known (e.g., [17][18][19].…”