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 degrees C using Lipozyme(TM). The reaction of method B using Lipozyme(TM) or the lipase of Candida antarctica in n-hexane at 60 degrees 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 mN m(-1) at critical micelle concentrations of 10(-5) to 10(-3) mol l(-1) at 37 degrees C.