TECHNOLOGY FOCUS - ORGANIC CHEMISTRY - Preferred Process: In the process, the reaction fructose and/or glucose-containing starting material with alcohol, is performed at 50-300 (preferably 125-250, more preferably 175-225)degrees C. At least one solvent or diluent is present in addition to the alcohol. The ratio of alcohol/solvent is 50-0.1 (preferably 20-1, especially 10-2). To initiate or regenerate the heterogeneous acid catalyst, an inorganic or organic acid catalyst is added to the feed of the fixed bed or catalytic distillation continuous flow process. The liquid hourly space velocity (LHSV) of 1-1000 (preferably 5-500, especially 10-250, and particularly 25-100, is used. The process is performed in a continuous flow process. The residence time in the flow process is 0.1 second to 10 hours (preferably 1 second to 5 hours, especially 1 minute to 1 hour). The continuous flow process is a fixed bed continuous flow process. The continuous flow process is a reactive distillation or a catalytic distillation process. Preferred Components: The alcohol is selected from the primary (un) branched aliphatic alcohols (preferably 1-5C primary (un) branched aliphatic alcohols, especially methanol, ethanol, 1-propanol, isopropanol and 1-butanol, particularly methanol and ethanol, more particularly ethanol. The acid catalyst is selected from the group consisting of solid (halogenated) organic acids, inorganic acids, salts, Lewis acids, ion exchange resins and/or zeolites. The acid is a solid Bronsted acid. The acid is a solid Lewis acid. The fructose and/or glucose-containing starting material is selected from starch, amylose, galactose, cellulose, hemi-cellulose, glucose-containing disaccharides such as sucrose, maltose, cellobiose, lactose (preferably glucose-containing disaccharides, especially sucrose or glucose). The solvents are selected from the water, sulfoxides (preferably dimethylsulfoxide) and ketones (preferably methyl ethylketone, methylisobutylketone and/or acetone). The fixed bed comprises a heterogeneous acid catalyst. EXAMPLE - In a continuous flow reactor, sucrose (10 mmol/l) dissolved in water/ethanol/sulfuric acid, was reacted at 195degrees C with a residence time of 6-60 seconds and a flow rate of 10 ml/minutes (i.e. 3.33 ml/minutes/reactor) to obtain 5-hydroxymethylfurfural ether and 5-ethoxymethylfurfural ether with a selectivity of greater than 90% at a conversion of 25%.