Enzymatic monoacylation of fructose by two procedures

Abstract

Two methods for the lipase-catalyzed monoacylation of fructose with long-chain fatty acids (e.g., palmitic, stearic) in hexane or 2-methyl-2-butanol are described. Using method A the enzymatic monoacylation of fructose was carried out at a molar ratio up to 15:1 of fatty acid to fructose in 2-methyl-2-butanol at 55°C using Lipozyme™. The reaction of method B using Lipozyme™ or the lipase of Canadida antarctica in n-hexane at 60°C was favored by a 1:3:4.5 molar ratio of fatty acid to fructose to phenylboronic acid; phenylboronic acid served as a solubilizing agent for the sugar in hexane. Method A gave a mixture of the C-1 and C-6 monoacylated fructose fatty acid esters, whereas for method B only the C-1 monoester was found. In each case pyranose and furanose isomeric forms of the sugar were apparent in solution. Typically, yields of about 40% were obtained. Adding fructose fatty acid esters to water lowered the surface tension from 72 to a minimum of 27 m n m −1 at critical micelle concentrations of 10 −5 to 10 −3 mol l −1 at 37°C.