Different strategies for selective monoacylation of hexoaldoses in acetone

Abstract

Experimental protocols for the selective production of 6-O-acylhexoaldose emulsifiers from precursor sugars (mannose, glucose, and galactose) and corresponding fatty acids are compared. The protocols employ an immobilized Candida antarctica lipase in a solvent (acetone) which is both easily eliminated and accepted by the European Economic Community for use as an extraction solvent in the manufacture of foods and/or food additives. This comparative study provides guidelines for selection of appropriate conditions for quantitative monoacylation of aldoses in acetone, on the basis of the solubilities of the precursor sugar and the monoester in acetone at different temperatures. Although relatively low temperatures (<40°C) favor precipitation of glucose monoesters, higher temperatures (e.g., 55°C) should be used to increase solubility of mannose and thus selectivity of the reaction leading to the mannose ester. Galactose is transformed with poor selectivity to the desired monoester by these procedures. Factors affecting the viability of these synthetic reactions in acetone are also discussed. JSD 1, 345-352 (1998). FIG. 1. (A) Effect of the molar ratio of lauric acid to glucose on the enzymatic synthesis of 6-lauroyl glucose. Conditions: 60 mg glucose, 2 mL acetone, 100 mg Novozym 435 (Novo Nordisk, Bagvaerd, Denmark), 200 mg of molecular sieves, 40°C. Lauric acid/glucose: • 6:1; ■, 3:1; ■ ■, 2:1; ▲, 1:1. (B) Effect of temperature on this reaction. Equimolar quantities of acid and sugar; •, 24°C, ■, 40°C; other conditions as in Figure 1A. Molar yields of monoand diesters are expressed in percentages with respect to the limiting reagent. 348 J.A. ARCOS ET AL.

Production and characterisation of enzymatically produced lauric acid esters of fructose

“…Reactions at different molar ratios of lauric acid to fructose (0.5:1, 1:1, 3:1, 5:1) were performed at 40 °C using acetone as a solvent. Acetone is accepted by EEC directive 88‐344‐CEE as a general use solvent in the manufacture of food additives 18. It is also cheap and easy to remove from the final product.…”

“…The diester was then eluted with 100 ml of a 99:1 (v/v) mixture of CHCl 3 and CH 3 OH. Finally, elution of the monoester was done with 100 ml of a 97:3 (v/v) mixture of CHCl 3 and CH 3 OH 18…”

Optimization of lipase‐catalyzed sorbitol monoester synthesis in organic medium

“…The synthesis of pure monoester is difficult when the polyol contains several primary hydroxyl groups. Several parameters have been shown to determine the proportion of monoester in the ester product (including the solvent system, water activity, and temperature) among which reaction time and acid/polyol molar ratio generally are key parameters (3,4,(8)(9)(10)(11).The purpose of this work was to study the influence of the last two parameters on the synthesis of monoester of oleic acid (OA) and sorbitol catalyzed by Candida antarctica lipase B (Novozym 435) in nearly anhydrous organic medium under reduced pressure, using the process described by Ducret et al (3). A mathematical model was developed to determine relationships between OA concentration (for a constant sorbitol concentration) and various parameters concerning product quality (percentage of monoester in total ester), downstream processing (monoester concentration, OA, and sorbitol conversion yields), and economical considerations (productivity).…”

“…The synthesis of pure monoester is difficult when the polyol contains several primary hydroxyl groups. Several parameters have been shown to determine the proportion of monoester in the ester product (including the solvent system, water activity, and temperature) among which reaction time and acid/polyol molar ratio generally are key parameters (3,4,(8)(9)(10)(11).…”

Regioselective lipase-catalyzed synthesis of glucose ester on a preparative scale

“…However, most of these studies were performed only on a milligram scale and relatively little attention has been paid to practical difficulties in the production of SFAE on a large scale, e.g. how to efficiently remove reaction water and the products from the solvent and how to properly regenerate solvents [6][7][8][9][10][11][12][13][14]. In our ongoing projects on the lipase-catalyzed synthesis of SFAE, we have described that SFAE can be obtained in a heterogeneous reaction system [15][16][17][18][19][20][21], in which most of the substrates (unmodified sugar and free fatty acids) are present in form of suspended particles and which contains a very small amount of solvent in order to maintain a catalytic phase.…”