Abstract: 5-(.alpha.-D-glucopyranosyloxymethyl)-furan-2-carboxaldehyde (GMF) is produced from isomaltulose by heating a solution of isomaltulose in a strongly polar aprotic solvent in the presence of an acidic ion-exchanger, either batchwise or by percolation of the solution through a column filled with the ion-exchanger. Novel derivatives of GMF of the formula (I) ##STR1## wherein R' is a hydrogen atom, an acyl group or an alkyl group and X represents --CH.sub.2 OH, --COOH, --C(H).dbd.NOH, --CN, --CH.sub.2 NHR" or --CH.dbd.CR"R'", where R" is a hydrogen atom, an acyl or aryl group or an alkyl group with up to 20 C atoms and R'" is a hydrogen atom, --NO.sub.2, --CN, --COOalkyl or acyl are described, and also their preparation and use for the preparation of surface-active compounds.